Issue 1 August 2020 QUARTERLYDOOT MAGAZINE OF THE INDIAN INSTITUTE OF ASTROPHYSICS

Are you stuck in the mirror universe? --Check it out

Understanding the significance of the A Tale of Two Eclipses insignificantUs

Errors are beautiful, Glimpses of memories Really...! --25 years of Hanle

To the edge of the Cosmos with Prof. Varun Sahni Director’s Message DOOT Quarterly Magazine of the Indian Institute of Astrophysics

Issue 1 Congratulations to the IIA student team August 2020 for bringing out the first issue of the e-magazine IIA Publication No.: IIA/Pub/DOOT/2020/Aug/001 DOOT. I am very happy that the first issue of this magazine is released by Prof. Avinash C. Pandey, Editors Panel the Chair of the Governing Council, in the presence of Prof. Ashutosh Sharma, Secretary DST and Prof. Sandeep Kataria (Chief Editor) Vijay Raghavan, PSA to honorable Prime minister. This year is very special, as IIA is celebrating its 50th Content Team Prof. Annapurni Subramaniam finished year of formation as a society and the Department Fazlu Rahman, Partha Pratim Goswami, Raveena Khan, her post-graduation from Victoria of Science and Technology is also celebrating its Soumya Sengupta, Suman Saha, S.V. Manoj Varma, College, Palakkad. She completed a 50th year of formation. Vishnu Madhu Ph.D. in Physics from the Indian Institute of Astrophysics (IIA) and Bangalore This e-magazine is an initiative of the Design Team University in 1996, with a thesis entitled ‘ students of the institute, to bring together Anand M N, Manika Singla, Prasanna Deshmukh, “Studies of star clusters and stellar interesting contributions to a larger community. Rishabh Singh Teja, Sarthak Choudhary evolution.” She became a Post Doctoral The idea emerged from the increasing demand Fellow at IIA in 1998. Currently, she on honing skill sets such as presentation, Advisers is a Professor and the Director of IIA. communication and expressing ideas effectively Dr. Maheswar Gopinathan Her major fields of research include through, writing and graphics from the younger Dr. Piyali Chatterjee Stellar Populations, Star Clusters, Stellar researchers. An enthusiastic and skilled team has Evolution, Galactic Structure, Magellanic put together a wonderful set of contributions Acknowledgment Clouds and nearby galaxies. Prof. including, articles, creative writing, experiences Special thanks to Mr. Prabhakaran (Prabhu) for permitting us Subramaniam was elected as the Fellow and astronomical photography. I am sure that st to use his Solar Eclipse image (June 21 , 2020) taken from UAE of Indian Academy of Sciences (FASc) this will be an interesting read to all age groups, in the DOOT title and Mr. Dorje Angchuk, IAO Hanle for the and the Fellow of National Academy of a sneak-peak into the world of astronomy and a cover picture. Sciences (FNASc). She has contributed special treat for budding science enthusiasts. I to India’s two major astronomy projects, request the IIA fraternity to make their contribution India’s first multi-wavelength astronomy to this magazine. I am sure that this will be a great satellite, AstroSat and the proposed learning experience for the entire team behind Thirty Meter Telescope which is the next this initiative. I look forward to the flow of future FAIR USE DISCLAIMER generation optical- infrared observatory. issues and my best wishes to the team. The primary intent of this magazine is for Non-profit, Education and Outreach purpose. The material used in this Magazine may be Copyright protected. Prof. Annapurni Subramaniam FASc., FNASc. Wherever possible permissions are obtained from the respective content owners. Director, Indian Institute of Astrophysics Appropriate credits are provided to the Owner & Original Source. DOOTQUARTERLY MAGAZINE OF THE INDIAN INSTITUTE OF ASTROPHYSICS

Invitation for the next issue From the Editor For the next issue of DOOT, we are inviting your contributions under the following categories:

Review Articles: Scientific and technical publications (recent publications in academic journals from the IIA family, IIA technical reports, breakthroughs in Astronomy, book review, Journal club discussions, milestones of IIA projects; to be published in simple language) are The Director-Students interaction in November 2019 seeded an idea for invited. Project interns and summer school project students can submit their results. (Word improving the writing skills among students through a magazine. This idea limit: 2000 words) seems to have double benefits, as an internal magazine allows the opportunity for students to review each other’s articles, and alongside it connects all the Physics Concepts made easy: For this section, we invite write-ups discussing interesting IIA family members. This idea has grown with the students’ and a few staff concepts of Physics in a very simple and enjoyable way, without using much of technical volunteers’ efforts and started producing its fruits. I remember that we (~5 jargons. The main motive is to reach a wider audience by making it easy to understand, students) had our first face to face team meeting in Bhaskara as part ofthe relate, or appreciate Physics, without having any technical background in the subject. (Word limit: 1200 words) magazine’s early planning. The new normal shifted all the planning sessions to an online platform with an increased team size of 12 members. From the time Individual Experiences and Substation stories: In this section, we invite stories of your we asked for this online magazine’s contribution, we feel encouraged to have personal experience, maybe with a scientific project, an experiment, attending a conference/ received enormous contributions from the IIA family members. workshop, a collaborative visit, visit to an observatory, or even a coffee break with a prominent scientist. We also invite interesting stories from our substations at Hanle, Kodaikanal, Our team hopes that all the IIA family members will share their Kavalur, and Gauribidanur about the ongoing activities and valuable memories. (Word limit: experiences through this platform in successive issues. The sustainability of 1200 words) this magazine certainly depends on the contributors to the magazine. We are Alumni and retired staff/faculty stories: IIA Alumni students and retired staff/faculty can excited to bring the first issue of this magazine. As it is our first experience, we share their motivational experiences in building up the IIA. (Word limit: 1200 words) would like to improve it with your generous feedback.

Creativity Corner: Splurge on your creativity here! For this section, we invite all kinds of artworks including but not limited to paintings, poems, short stories, and graffiti. (Word Dr. Sandeep Kataria limit: 800 words) Chief Editor, DOOT

Disclaimer: Any article received will be published only after strict screening. The chief editor’s decision will be final.

We would like to improve the content of the magazine. Please send your generous feedback and contibutions for next issues to [email protected] CONTENTS

Featured DOOTQUARTERLY MAGAZINE OF THE INDIAN INSTITUTE OF ASTROPHYSICS ‘Miles to Go to the 11 Edge of the Cosmos’ Experiences Creative Corner

A Tale of Two Eclipses 8 Glimpses of memories 21 Stillness 22 at Hanle during July Poem Part 1 29 Oh...Wind... Poem 24 To ‘if’ or to ‘when’ 33 Meeting the Milkyway that is the question 37 Swami Vivekanand Calligraphy 39 First Light with UVIT Detection of a dead 42 The Universe, 30 companion to a An Occult - Poem Vampire star in the 45 The shining eyes Globular Cluster of 48 The Exoplanets Painting’ our Galaxy 52 Passo del Tonale 51 More than me - Errors are beautiful Poem 35 and Gaussian 55 My life at IIA 57 Around you Really? Painting The Cover Picture 64 Experience at IIA and I rarely come in front of a camera since I am much happy on the other side of it. Recently there was Mystic You Testing Theoretical a broad research 67 some problem with my camera and after many days of thoughts, I was able to rectify it. So excited 43 Poem Bar Formation philosophy was I, that I decided to utilize the full moon and take some beautiful pictures of the Hanle Dark Criterion Sky Sanctuary. I have been thinking of a shot with the ice, inspired by Paul Zizka. During the shot I found that the cracks were good, but the same was not getting justified without any prop. Also it is very difficult to bring someone out of their comfortable beds with me in -10 OC. I had no other Zeeman Effect 49 Observations choice but to get a self portrait to justify the Ice. The artificial lighting was done with a lume cube underneath me in one of the cracks and the green cast is due to the colour of the jacket and pants. 28 Sky Map - 48 Annular Solar Eclipse 60 A tale of hydrogen- August 2020 26th December 2019 deficient stars Portrait of a Stargazer ISO : 400 38 Timeline of 58 Sky Map - - With Orion, Hyades and Pleiades from left to Post processing : Photoshop. Eclipse over IAO October 2020 right, and the natural lighting provided by the How to know if you 65 Supermoon at Hanle Dark Sky Sanctuary. Panorama of 2 shot, 1 for the foreground and are stuck in the 41 Sky Map - 68 Once in a life time September 2020 Capturing the Comet 2nd for the sky with same settings and tripod “mirror universe”? NEOWISE Camera Exif: location. Camera : Sony A7S II Lens : Sigma 20mm at f/5 Mr.Dorje Angchuk Exposure : 30 sec Engineer-in-Charge, IAO, Hanle DOOT Indian Institute of Astrophysics IIA Stories IIA Stories Indian Institute of Astrophysics DOOT Asst. Commandant, ITBP are seen in these During July 1996, first AWS (Automatic Weather photos. A stone pileup sacred ‘Mane’ is there Station, Campbell Scientific Inc.) reached Hanle. in the background. Prof. Harish has put a note We transported it to SW base of hill in the early of this visit in our log-book. I could get a photo morning on July 17, 1996 by Jeep and then also.

Glimpses of memories at Hanle during July Indian Astronomical Observatory: 25 Years

Prof. B. C. Bhatt Part 1 loaded the boxes on mules for transporting Dorje Angchuk the consignment top. A team of myself, Prof. Man Singh Tushar Prabhu and Mr. B. N. Naidu (from IIA) also climbed to the top with other helpers. The AWS was installed by noon and we got the first

Preamble

Under the Himalayan Infrared 1995, we traveled Optical Telescope (HIROT) to the SW side of project, the first team of IIA the hill and climbed landed at Leh in November 1994 to the top in late and with initial acclimatization evening. By the On July 8, 1995, Gen. K. V. Krishna Rao, then in high altitude and cold time we reached Governor, State of J&K State landed on ITBP weather, this team arrived in Digpa-rtsa-re top, camp helipad near our setup. After visiting Hanle in December 1995. We it was dark and ITBP, he came to our setup also and Prof. pitched our setup in a mud-hut we spent 3-4 hours Harish welcomed him. He gave a briefing on result at 1300hrs 17/7 which we could see by in the premises of ITBP Camp in in night there. We our project. He appreciated IIA’s effort in that downloading data on a portable storage module Hanle. This camp is situated in the North-East experienced the Hanle sky from top for the first tough terrain for the project. Prof. Harish had connecting to PC in the evening at our Camp. of our aimed Digpa-rtsa-re hill. To approach time and tried to judge the quality of sky. As it put a small note on our log-book about it as seen After installation we climbed down and cooked this hill, we have to walk about 4-5 km to Tashi- can be noticed that we are at the topmost point in the photo. our food (Mr. Man Singh, Leh) near a spring at Chholing Gompa or travel approx. 12-14 Km to of hill and Prof. Harish was looking at the sky base of the hill. the base of the hill in the South-West direction with Binocular. Myself, Mr. Venkataramanan and then climb steep 1000 ft to reach the top of (VBO), Kunga Tsering (Hanle) and Mr. B. Sinha, the hill. I was a member of this team and stayed in Leh/Ladakh for an extended period. I have some fond memories of Leh/Hanle and I would like to share it every month in this new IIA messenger magazine, ‘Doot’’ under the title From IIA, wooden panels arrived at Hanle and “Glimpses of memories at Hanle during July”. we erected one enclosure ourselves at Hanle top and 12 inch Meade telescope was installed During 1995, Prof. Harish Bhatt was the over the roof on this structure. Dome and other coordinator for our group at Hanle. On July 5, fabrication was completed at the site only with 8 August 2020 August 2020 9 Indian Institute of Astrophysics DOOT Indian Institute of Astrophysics IIA Stories Interview DOOT

‘Miles to Go to the Edge of the Cosmos’ Professor Varun Sahni speaks about his exciting career, childhood days, PhD life in Moscow and his views on the future of cosmology

Fazlu Rahman and Sandeep Kataria

Let’s begin with your academic life and exciting the locally available resources and helping research activities. After bagging years of experience hands. This telescope was used for seeing abroad working with great scientists like Yakov measurement at the site with Differential Image Zeldovich and Alexei Starobinsky, you have been there Motion Monitor (DIMM) method. Beside it, we Dr. B. C. Bhatt joined IIA in 1994 and was in the forefront of scientific research in the country for erected a 220 GHz radio sensor for measuring part of the first team of IIA that did the site- the past three decades. How would you look back on precipitable water vapor, made by joint efforts of testing and characterization of Hanle, Ladakh in November 1994. He was the Project Officer your career as a cosmologist? IIA, RRI and Japan. for setting up the 2 meter HCT at Leh/Hanle. Currently he is a professor at IIA and Scientist- in-Charge CREST campus, Hoskotte. It has been a very satisfying experience. My PhD work in Moscow was done under the guidance of two Mr. Dorje Angchuk was the first person from great Russian theorists. Additionally, Moscow State Ladakh to join IAO as a Trainee Engineer during University was well known for its fine physics and its initial phase. He contributed to the installation and commissioning of the 2 meter HCT, later maths departments. As a result, I was exposed to the getting a permanent position there. Presently he Professor Varun Sahni is an Indian science of a very high order, which inculcated in me theoretical physicist, astrophysicist and is Engineer-in-Charge, IAO. an appreciation for high-quality scientific research and a distinguished professor at the Inter- endeavor. Mr. Man Singh joined as Cook/Caretaker at University Center for Astronomy and IIA’s transit guest house, and was later posted Astrophysics (IUCAA), Pune. Known for as Caretaker, IAO, Leh. During this time, he his research in cosmology, Sahni has studied I should add that when I started working in Liquid Nitrogen Plant: A modular Liquid supported the guest houses at Leh and Hanle the universe, more specifically its large-scale cosmology, it was still not a very popular field, and Nitrogen Plant purchased from M/S Sterling including office related work. He is currently a structure, the early inflationary phase, and most of the great discoveries in those days were Cryogenics and Refrigeration BV, the UDC at Raman Science Centre, IAO, Leh. its accelerated expansion. Prof Sahni is a coming from other disciplines such as high energy Netherlands. The installation of this plant was recipient of the Bhatnagar Award (2000), a physics. Even when I returned to India in 1991, done at the base camp in July 1999 with the help fellow of the three national science academies cosmology was primarily driven by fine theoretical of M/S Philips India. It has a capacity of 5 lit/ and The World Academy of Science (TWAS). ideas. hour liquid nitrogen production. This complete plant was designed by a company keeping in For DOOT magazine, he spoke to Fazlu All that changed in 1992 with the discovery of mind the harsh and tough weather conditions in Rahman and Sandeep Kataria about his academic life, childhood stories, PhD days in fluctuations in the cosmic microwave background Hanle. Moscow, his interests in arts and science, and made by the Cosmic Background Explorer (COBE) his views on the future of cosmology. telescope which placed the standard model of

* Authorship and photo credits : Prof. B. C. Bhatt, IIA, Bangalore, Mr Dorje Angchuk Mr. Man Singh, IAO, Leh. cosmology on a firm foundation. 10 August 2020 August 2020 11 DOOT Indian Institute of Astrophysics Interview Interview Indian Institute of Astrophysics DOOT a lecture on my findings in from primordial gravity waves, which could determine the paper in 1980! The very next Cambridge. One of the great which in addition to density properties of the cosmic web year I embarked on my MSc moments of my life was fluctuations, are also a generic in a very precise manner with Alexei Starobinsky, discussing the no-hair theorem prediction of the inflationary using elaborate concepts from who suggested an interesting in the presence of Stephen scenario. I had then just joined differential geometry and problem involving quantum Hawking, who asked several IUCAA, and a clever young topology. particle production in the deep and perceptive questions. PhD student was working with vicinity of black holes. This, (My paper on the no-hair me -- Tarun Souradeep. Tarun I am very happy to see that our too, turned into a research theorem was written jointly and I began to work intensively Shapefinder work has become paper. So even before with Hawking’s former student on this problem and wrote a quite popular, and aside from embarking on my PhD, Ian Moss.) nice paper which was the first being applied to the study of under the joint supervision of to extensively analyze the effect the cosmic web, it is also being Zeldovich and Starobinsky, My next exciting research of gravity waves on the CMB. widely applied to fields as far I had already published two Varun Sahni (center) during his PhD defence in 1985 flanked by his supervisors moment came with the This paper was part of Tarun’s apart as nanoscale physics, the single-author papers in reputed Yakov Zeldovich (right) and Alexei Starobinsky (left). discovery of tiny fluctuations thesis and inspired him to magnetic dynamo, combustion international journals. Photo credit: Varun Sahni in the CMB made by COBE embark on a career dedicated physics, turbulent flows, etc. Ever since then, exciting waves, the cosmic web, dark in 1992. I remember very to understanding the CMB. It is always very gratifying to Soon after the discovery of observational discoveries energy, etc. Would you like clearly that a copy of the press Since then, Tarun has written see one’s research is applied dark energy, I became heavily have been made almost every to share some of your eureka release was circulated to us by some very fine papers on this to fields other than the one for involved in developing ‘model- other year. I never would have moments with us? a good friend in TIFR. I was subject, guided over a dozen which it was intended! independent’ techniques guessed, returning to India in completely astounded to hear PhD students and become which could differentiate 1991, that within the coming During my post-doctoral of this discovery. Scientists had one of the emerging leaders of In retrospect, it is interesting evolving dark energy three decades so many exciting years, I helped in proving a been looking for fluctuations Indian science. that these two academically models from the unevolving observational discoveries cosmological ‘no-hair theorem’ in the CMB for almost two quite distinct directions, cosmological constant. Two would have happened in by demonstrating that inflation decades, and none had been In parallel with working on namely the quantum of these diagnostics: Om and cosmology, out of which could arise from a very wide found. Some scientists were gravity waves and the CMB, I production of gravity waves the Statefinder have become three were even awarded the class of initial conditions, even calling this a failure of decided to understand other and the structure of the cosmic quite popular and have Nobel prize: one for the COBE including space-times that the big bang model! All this aspects of cosmology including web, emerged from two pre- been successfully applied discovery of anisotropies were initially expanding changed in 1992. the formation and evolution of PhD projects in Moscow. The to different dark energy in the cosmic microwave anisotropically. Remarkably, superclusters of galaxies and first involved a take-home models. I am confident that background (CMB), another for inflation acted as a Universal The importance of the COBE cosmic voids, which intertwine exam, which I gave to Prof. the application of Om and the the discovery of dark energy Isotropiser and isotropised a discovery lay in the fact that to form an exceedingly Zeldovich for his wonderful Statefinder to high-quality data and a third for the discovery of universe that expanded at it informed us that galaxies elaborate structure called the course on Cosmology. expected in the near future gravity waves. different rates in different arose out of tiny fluctuations cosmic web. My mathematical Zeldovich liked my new will help address fundamental directions and so did not (1 part in a 100,000) created in training in Moscow (which solution to his assignment questions about the nature Looking back, I am exceedingly resemble ours! the early universe, perhaps by included a course on topology) very much, and aside from of dark energy and deepen glad that I chose cosmology as a process called inflation. So greatly helped me in this awarding me with an A our understanding of this my discipline way back in 1980 The no-hair theorem now theorists knew the initial endeavor and together with my grade also suggested that I important issue. (when I wrote my first paper). considerably enhanced the conditions which later grew to collaborators Sergei Shandarin write a paper on gravitational theoretical appeal of the become galaxies. I immediately and B. S. Sathyapraksh, I clustering in the universe (the I should add that good science You have made remarkable inflationary scenario, and realized that a small part of the discovered an exciting new topic of my assignment). Thus is usually the by-product of a findings on topics like gravity soon, I was invited to deliver CMB fluctuation could arise diagnostic called Shapefinders, emerged my first scientific generous collaboration. My

12 August 2020 August 2020 13 DOOT Indian Institute of Astrophysics Interview Interview Indian Institute of Astrophysics DOOT work on Om and the Statefinder instead the universe contracts, which is fueled by an unknown useful and important. Recall to resemble the Big Bang 1914 (around the same time involved a collaboration bounces, and then expands energy source having negative Hubble’s discovery of an model in which galaxies once as Wegener’s discovery), between myself, Prof. thereby accommodating the pressure and called dark expanding universe. It is very close together are now moving and Eddington organized Starobinsky in Moscow, and possibility of an infinitely old energy. easy to understand cosmic apart.) a difficult experiment in its my Ph.D. students Ujjaini cyclic universe. expansion in terms of Einstein’s support. (Recall that Eddington Alam, Tarun Deep Saini, and Swagat and I are proposing theory of general relativity. I Unfortunately at the time, no organized his expedition to Arman Shafieloo, all of whom What is your current focus of an elegant unification scheme sometimes wonder how one one paid much attention to Africa in 1919 when the world wrote excellent PhDs and are research? in which both early and would have interpreted this this important idea mainly war was raging in Europe, and now accomplished scientists. late-time acceleration are discovery had Einstein’s theory because continental drift did with Einstein and Eddington My most recent work has explained in a concise manner not appeared on the scene. not have a firm theoretical belonging to countries formally I am also investigating the focused on the creation of within a common theoretical underpinning. Some geologists at war with one another.) This exciting possibility that the tiny black holes in the early framework. I am sure our In this connection, you may even mocked Wegener’s idea, story never fails to inspire present acceleration of our universe. Swagat Mishra (my paper will be of interest recall that somewhat before and he was given a hard time. me since it shows us the universe is not caused by an PhD student) and I have shown to cosmologists once it is Hubble made his important All that changed with a deeper universality of science and the exotic form of matter such as that black holes ranging in size published. discovery, Alfred Wegener, understanding of the Earth’s extraordinary cooperation, dark energy but arises because from only a few angstroms to in 1912, made an equally interior, so much so that across nations, that is required our universe is five (and a mass greatly exceeding that Cosmology is now in the phase important observation Wegener’s idea now constitute to ensure its success. not four) dimensional. Such of the sun, could be produced of intriguing observations, pertaining to our planet Earth. mainstream geophysics and it’s models are usually referred in copious amounts in the thanks to the set of powerful Wegener noticed that the common knowledge that the I, therefore, believe that to as Brane-worlds since our early universe during inflation. telescopes available. The last boundaries of the different continents are part of Earth’s observational discoveries occur 3+1 dimensional universe These so-called primordial seventy years have witnessed continents fit into one another crust which drifts on a semi- in two distinct ways: 1. An can be visualized as a mem- black holes could be an significant progress in our interesting theory makes new brane, which is embedded interesting candidate for dark theoretical understanding too. predictions and observations Recall that Eddington organized his expedition in a higher dimension. This matter. Our model provides an As a theoretician, how do you are designed specifically to to Africa in 1919 when the world war was raging model, proposed jointly alternative mechanism (to the look into these developments? test them. 2. Observations in Europe, and with Einstein and Eddington with Ukrainian scientist Yuri usual ‘exploding stars -> black Do you think that we are at the appear unexpectedly, which belonging to countries formally at war with one Shtanov, fits the data very holes’) for the creation of black edge of our lifelong efforts to take us by surprise and add another. This story never fails to inspire me well and is, therefore, being holes indirectly seen by recent understand the cosmos? a new dimension to our since it shows us the universality of science and taken quite seriously by the gravity wave measurements. understanding of nature and to the extraordinary cooperation, across nations, cosmology community! A very beautiful Jugalbandi our theoretical investigations. that is required to ensure its success. One of the most intriguing exists between theory and Yuri and I have explored an aspects of the cosmological observations. Sometimes The discovery of the CMB even more exotic idea, namely model is that the universe theory is ahead of observations, like pieces in a jigsaw puzzle molten Magma. This process is by Penzias and Wilson in the that our universe could have appears to accelerate twice, and sometimes it is the other and also that similar plant known as plate tectonics, and, 1960s and the later discoveries two ‘time’ dimensions instead initially at very early times in way around. In fact, I cannot and animal fossils were seen on its basis, continental drift of anisotropies in the CMB of one -- with ‘time’ playing a process called inflation, and see progress in cosmology on different continents. To appears natural.Unfortunately, by the space satellites COBE, the role of the fifth dimension. then about 14 billion years later happening in any other way! explain these observations, a hundred years ago, when this WMAP and Planck belong A nice feature of this model at the current epoch. Although Wegener proposed the theory idea was first proposed, it went to the first class since the is that it cures cosmology of the discovery of cosmic Cosmology has clearly of continental drift according largely unappreciated. prediction of relic radiation the initial Big Bang singularity acceleration was awarded the benefited from observational to which long ago the different existing from the big bang at which the density of the Nobel prize, we still do not discoveries in a very direct continents were all joined So in a sense, it was lucky (then called the Primeval universe becomes infinite. No understand the precise reason way. But the underpinning that together and were now moving that Einstein discovered Fireball) had already been infinities occur in our model, for the current acceleration, theory provides is also very apart. (Pictorially, this appears the theory of relativity in made by George Gamow 14 August 2020 August 2020 15 DOOT Indian Institute of Astrophysics Interview Interview Indian Institute of Astrophysics DOOT and colleagues in the 1940s. the Universe. extremely radical implications On the other hand, many drain in which one had to lie moons, stars, and galaxies. I However, the discovery of for cosmology, including the students love numerics and face down with our fingers especially loved pictures of Hubble expansion, QSOs, and Perhaps similar advances may possibility that our entire data sets, and to them, I give pressed against our ears in case galaxies, which captivated my more recently, dark energy be in store for us now almost observable universe forms only projects which test a theory a bomb exploded nearby. As imagination. belongs to the second class a hundred years after the a small part of an infinitely against the latest observations. time passed, we became real since they took most theorists Hubble expansion and general diverse universe, with each That way, the student enjoys experts at this exercise, and no Very soon I asked my parents by complete surprise. relativity were discovered. smaller component (baby his/her work, and the PhD sooner did we hear a whistle to buy me a telescope. I had Satellites such as Euclid may universe) having its own thesis proceeds smoothly. than we hurried towards our seen one in the display window Going by these examples, I inform us whether dark energy fundamental laws. It would be But it requires some effort on shelter. of a hobby store in Connaught feel that future observations is evolving or whether it is wonderful if one could come one’s part to be able to gauge a Place in Delhi, and I wanted will also broadly belong to one the cosmological constant up with observations to test student’s aptitude correctly. On one particular night, an it very much. But it cost 100 of these categories. The very proposed by Einstein way back this radical idea! interesting thing happened. rupees, which was a serious large galaxy surveys being in 1917. Cosmology has many We are very eager to know We were all fast asleep in our sum of money in those days. planned, such as DES, Euclid more unanswered questions. One also hopes that cosmology about your childhood days. dormitories when we heard the Nevertheless, my parents and SKA, are sure to shed These include the physics would help answer other Have physics and mathematics shrill sound of a whistle. We promised to buy me a telescope light on the nature of dark behind the matter-antimatter questions of great importance always been your favorite jumped out of bed, grabbed if I would get a first division energy and map the cosmic asymmetry observed in the to high energy physicists subjects? What motivated you our dressing gowns, and ran in my exams. I told them this web to unprecedented detail, Universe (and related issues such as the existence of extra to pursue science, particularly outside towards our shelters. was a trivial matter, but try providing much new fodder such as baryogenesis and dimensions -- an idea that has astrophysics, as your career? Suddenly we heard our teacher as I might I never scored over for theorists like me. leptogenesis -- the origin of been around almost as long as say: ‘stop stop, don’t run, look 57% in class. One year passed baryons and leptons and the the theory of relativity. My very early childhood days up, look up towards the sky’. and then a second. Finally, And yet one hopes that large photon to baryon ratio), were spent in a boarding I did so, and what I saw there my parents relented. They surprises will also be in store the nature of dark matter and You already spoke about the school near Shimla. There was amazed me. It was a comet !!! I probably realized that their for us and will propel science the origin of neutrino mass. role of students in your work. very little light pollution in had never seen a comet before, son would never cross the into different avenues and Most of these questions require Can you please tell us your those days, and so we could and it appeared to fill the entire 60% mark, but that should not directions. answers from physics, which experiences as a mentor? see distant objects such as the sky. What a spectacular object! stand in the way of him being lies beyond the currently nearby mountains and even To this day, I feel it was the allowed to pursue his passion; Recall that in 1900 Lord known (and well established) I regularly teach a few courses forest fires very clearly. most heavenly and beautiful so very soon my father took Kelvin addressed the standard model of particle which are largely liked by sight I have ever seen in my me to a shop in Old Delhi and British Association for the physics. The theoretical students, but most of my effort In 1965 a war with Pakistan life. bought me a lovely Japanese Advancement of Science with underpinning for inflation has gone into research and the broke out, and the nearby city telescope for the princely sum the words: “There is nothing and dark energy also requires training of students at the BSc, of Ambala was heavily bombed I don’t think I was the same of Rs. 310/-. It was mounted on new to be discovered in looking beyond the standard MSc, and PhD levels. by the Pakistani air force. The person after that night. The a small tripod, and I adored it! physics now. All that remains model. school authorities were worried fascination of the night sky and is more and more precise While working with students, that similar attacks might occur its beauty filled my mind, and Luckily for me (but unluckily measurement.” Nothing Therefore, further advances I try my best to grasp their near our school, and so we as I grew up, I started looking for the country), the year I got could have been further from in cosmology will necessarily strengths and preferences for were made to undergo serious out for books on astronomy. my telescope (1971) marked the truth since revolutionary depend on a deeper research work. For instance, air-raid exercises. These mostly yet another Indo-Pak war. This discoveries such as the theory understanding of high energy if a student loves doing amounted to running towards I especially loved books time the Pakistani air force of relativity and quantum physics and string theory. I analytical calculations, I place the nearest air-raid shelter published by Mir publishers came as close as Delhi -- my mechanics were just around the should add that recent ideas before him/her a challenging when the designated whistle of Moscow, who explained in home town, and three of their corner and changed our whole in string theory, such as the theoretical problem involving was blown by a teacher. The simple terms celestial objects planes were downed just near understanding of nature and multiverse scenario, carry new and difficult calculations. shelter was usually a clean such as planets and their the city’s outer defenses. 16 August 2020 August 2020 17 DOOT Indian Institute of Astrophysics Interview Interview Indian Institute of Astrophysics DOOT You are a scientist from the parents noticed that I was fond physics student but also a great family of actors, writers, of music and helped nurture lover of Hindustani classical and artists -- your father my passion. My mother music and played the flute. So Bhisham Sahni was a well enjoyed singing Hindustani after classes, we would jam known Hindi writer and your classical, and my sister played together -- him on the flute and uncle Balraj Sahni is a famous the piano, so I too learned the me on the guitar! We became actor. Can you tell us how piano, and a little later started quite good and even started you could integrate these ‘two playing the guitar. Later in performing at public music cultures’ in your life? school and also in college, I events in the city. After my BSc acquired quite a nice collection in physics, I left for Moscow Arts and science were never of music, including rock and for further studies, while Omar separate in my life. I come from classical. I believe this long soon left for the US, where he a family with a strong literary exposure to music rewired my completed his PhD. background, and no one in brain, and very soon, my marks my family had engaged in any in maths started improving. So all through my life form of scientific activity before (Also our maths teacher was appreciation for the fine me. My parents noticed my changed.) arts has complemented my

Varun Sahni with his PhD supervisor Alexei Starobinsky and his PhD student Swagat Mishra, at IUCAA. inclination towards science and (deep and passionate) love Photo credit: Varun Sahni readily bought me books and So by the time I reached the for science. My father always other material for experiments 11th class and was studying for encouraged me to read good -- I even made a small radio, the boards, I was beginning to books, and there was never any Because of this, strict vigilance looking at the bewildering books, and watch educational of which I was very proud. enjoy physics and maths and dearth of them in our house. began to be observed in the plethora of stars, planets, and programs on TV. If possible, Unfortunately, I did not receive also spent my leisure hours Later in Moscow, I discovered capital, and the windows of all constellations in the sky. The they should also become any encouragement towards going for long walks and that the schism between houses were painted in black to telescope was my companion, members of an Astro-club science in school since my playing my guitar. Surprisingly arts and science, which prevent light from leaking out and I would first point it at (or a similar popular science maths teacher was a big bully (for my parents and teachers), unfortunately existed in India, into the night sky. Jupiter, then at Saturn, then at activity) in their cities and try and frequently thrashed us, I cleared the 11th class with a did not exist in Russia, and I the Moon. On many occasions, to design simple experiments kids, for no real reason. The distinction in maths and a very was pleasantly surprised to see Despite the difficulties posed our relatives, friends, and (such as making your own relentless beatings from the high overall score, which got my fellow students engaged by the war, this was truly a neighbors would also enjoy the telescope), which can provide a math teacher made me fear me admission into St. Stephens in all kinds of activities that heavenly time for skywatchers wonders of the night sky. (One lot of joy. school very much, and my college, then the number one complemented physics. To astronomy enthusiasts. The could see well over a 1000 stars marks in that subject dipped to college in Delhi University. give one example, our physics lack of light pollution made on a clear night in those days.) Too much focus on rote a new low. (One of the reasons hostel had a lovely music the night sky pristine and learning is a really bad thing, I could seldom reach the In college too, I balanced my room fully equipped with beautiful. During summer, our Your own story shows the and Indian school children coveted 60% mark in school.) academic activity with extra- instruments, including a piano. family invariably slept on the curiosity of a kid to know suffer a lot on this score. The curricular fun. I became a I soon realized that some rooftop (barsati) of our house the cosmic wonders. What excessive attention to marks Despite this rather negative member of the chess club of my physics friends were to escape the summer heat advice do you like to give those and exams is a big spoiler to school atmosphere during my and joined the rifle shooting exceptionally talented (there being virtually no ACs children who aspire to be the true learning. Therefore much early years, something quite club to eventually become its piano players and played in those days). Although my next-gen scientists? more attention must be given remarkable did happen. And captain. Moreover, my college that instrument like semi- parents slept soundly, I could to creative activities and the that was my interest in music. lab partner, Omar Ahmad professionals. Others were very never fall asleep and would Kids must develop good development of imagination. Ever since I was a child, my Karim, was not only a fine well versed in literature and spend countless moments hobbies, read popular science 18 August 2020 August 2020 19 Indian Institute of Astrophysics DOOT Interview Creative Corner Indian Institute of Astrophysics DOOT poetry, and some loved good supervisor, was a huge music Finally, what is your message cinema. In fact, my cosmology store. So every time after for budding astronomers like teacher and guru, Prof. meeting him, I would go and us to keep us motivated in the Zeldovich, often opened his purchase long-playing records field? lectures by quoting from well- (LPs) and soon acquired a known poets and writers. collection of several hundred Love doing science but Stillness LPs, including the complete remember to mix it with other Akanksha Kapahtia Because of this eclectic works of Beethoven and plenty activities which you enjoy and Post-Doctoral Researcher atmosphere, I felt very much of Rock music (which was which provide you with a nice at home in Moscow and soon banned in Russia in those days break when you need it. Also, Look at the tree, firm in its place, collected a small library of and which I procured from try and have enriching summer brimming with flowers when seasons shower books, which included works abroad). or winter holidays when you grace, in science (the full 10 volume can forget all about work. yet; set of Landau and Lifshitz) What activities do you shedding its might, as well as literary classics. I do apart from the regular The mind is a sensitive when the autumn winds arise. should add that despite its academic works? instrument, and it needs both many drawbacks, Soviet-era work and relaxation to perform Look at the lake, no splashes no waves; socialism had one big plus I start my day with a bit of well. Also, each person’s like a canvas of the sky, point: books and music were Yoga and some meditation. I mind is unique, so try and through every night and day. heavily subsidised by the think a period of quietude understand yours! government. There were over especially in the morning, helps Look at the hill, sturdy in its ways; a dozen book shops in the with the rest of the day (which humming through the pines, university, and our physics can sometimes turn very seems stubborn at first gaze. department and the physics hectic). hostel each had its book shop Look at the sky, as clouds pass by; where one could find cheaply I continue to enjoy reading and like a mirage of the cosmos, priced excellent books. The playing music. My guitar is my till the stars appear high. Russians also had an excellent favourite companion, and I translation agency, which carry it with me everywhere Look at your mind, stillness is its way, translated the best foreign I go. I also love collecting old amidst rhythm of breath or lull of thoughts language books into Russian. coins and have a nice collection gone astray; So one had access to the best of ancient Indian and foreign yet; physics books written in coins. (My oldest coin goes it stays there aground, Japanese, French, Russian and back 2300 years.) Through waiting for itself to be found. Italian. I still own a book by coins, I have learned a great Enrico Fermi, written in Italian deal of history! I also enjoy Fazlu Rahman is a Senior on one page and in Russian on occasionally acting in plays and Research Fellow at IIA. the next! staged several of them during He works in the field of IUCAA’s foundation day. observational cosmology. To my good fortune, located Some years ago, I even acted in Sandeep Kataria is a Post near the Landau Institute, a feature film. Doctoral Researcher at IIA where I used to meet my PhD working in galactic dynamics.

20 August 2020 August 2020 21 DOOT Indian Institute of Astrophysics Review Review Indian Institute of Astrophysics DOOT

Fun fact #2: The founder of prestigious journals Science (Thomas Edison) and Nature (Norman Lockyer) participated in the expedition of A Tale of Two Eclipses the 1878 eclipse.

Sarthak Choudhary

Photograph of the Sun’s corona taken by Henry Draper during the solar eclipse of 1878.

couldn’t convince the the prevailing theory on the totality lasted for a little astronomy community that gravitation formulated by under 7 minutes. It was during they had sited Vulcan and Sir Isaac Newton which was these seven minutes that the On July 29th 1878, residents to measure small changes in Edison’s equipment proved thought to be working well at astronomers had to capture the of Rawlins, USA were ready ambient temperature during Eddington wanted to be too sensitive to measure the time. Eddington wanted precise location of preselected with their smoked glasses to the eclipse. The scientific to prove General the temperature variations to verify Einstein’s theory stars in the sky. When the witness a spectacular show of motivation for the party to Relativity, according caused by the eclipse. which says that gravity is the photographic plates were the celestial hide and seek - a travel all the way to Rawlins to which gravity However, Draper did manage manifestation of curvature of analyzed from the expedition total solar eclipse. Astronomers enduring dust storms on was a manifestation to photograph corona. The space-time caused by a massive and the results of the shifts from all over the world had their way was to look for the of curvature of irregular orbit of Mercury was body. To do so, Eddington in the star positions were already arrived in the town. signs of a planet between Sun spacetime caused later explained by Josef Lense and astronomer Frank computed, the results matched Amongst those was a party and Mercury. Astronomer by a massive body and Hans Thirring using Albert Watson Dyson had designed with the GR predictions of astronomers led by Henry and mathematician Urbain Einstein’s General Relativity an experiment where Sun, to a very high degree of first planet whose existence Draper and accompanied Le Verrier had predicted a (GR). Moon and other stars were accuracy. The success of the was predicted before it was by inventor Thomas Edison hidden planet to be the cause the apparatus. To prove that expedition came in the form of ever observed by a telescope. who had already set up a for the orbital precession of the In 1919, an astronomer a massive body such as our observational proof of general Could there be another temporary observatory by the name of Sir Arthur Sun indeed can cause space- relativity which catapulted one, an entire planet for this day. But what Fun fact #1: Both of the phenomena Stanley Eddington would time distortions, one needs to Einstein into an international lurking between was the purpose of their which motivated these expeditions reach Príncipe off the coast observe a star, once when it is fame. Sun and Mercury? visit? Henry Draper was a were explained by the same theory. of West Africa as a part of close to the Sun and once when Astronomers of the day famed astrophotographer, another expedition to catch it isn’t. No stars are seen in had even named the he wanted to photograph the perihelion of Mercury. Urbain the glimpse of an eclipse. This the daytime, hence one must undiscovered planet- ‘Vulcan’ corona of Sun, and left all had previously predicted the time the goal wasn’t to find wait for a total solar eclipse. Sarthak is a Junior Research after the Roman God of fire, the scientific data gathering existence of an eighth planet an unseen planet but rather During a total solar eclipse, Fellow at Indian Institute of not the homeworld of science Astrophysics. When space and to his colleagues. Thomas beyond the orbit of Uranus improve our understanding the sky turns dark albeit for officer Spock. The expedition time permit he likes to write Edison wanted to test his which proved to be correct. of the cosmos. General a very small period. For the about history of science wasn’t particularly successful, new invention, ‘tasimeter’ The planet Neptune was the relativity had challenged eclipse of 29th May 1919, [email protected] the astronomers 22 August 2020 August 2020 23 DOOT Indian Institute of Astrophysics Physics Concepts Physics Concepts Indian Institute of Astrophysics DOOT

Understanding the Significance of the insignificant Us, in living with our star - THE SUN

To ‘if’ or to ‘when’ that is the question Understanding our nearest star, the Sun

Satabdwa

Man had been living under Figure 1: Someone once said “Beauty lies in the eyes of the beholder.” The Sun is a burning example The Sun has been one of the biggest reasons of these words. Images of the Sun taken in different wavelengths by SOHO/NASA the mercy of nature from the for the sustenance of life on our planet. We days of folklore. It was only have heard from our school days that the Sun derived from ancient Greek, from which light escapes from Convection and radiation are after the dawn of civilization, is a blazing ball of fire, it is the reason behind with photo meaning light, the Sun and reaches our eyes, two different modes of transfer that we started taming nature, every bright mornings that we wake up to, the and thus referring to the and we are able to see it. As the of heat from one point to forgetting the fact that when mystique cycle of seasons that we enjoy. spherical surface that emits density of the solar atmosphere another. The difference in the nature shows its displeasure light), the chromosphere decreases with height, the outer two can be easily visualized. all of a sudden, we are nothing morning that we wake up to, that. It is neither a solid, nor a (chromo meaning colour, atmospheric layers become If you take a ball and throw more than flies in the hands the mystique cycle of seasons liquid or gas, but is made up named due to its reddish fainter, which makes it difficult it to your friend, then neither of wanton boys. As the light that we enjoy. In a nutshell, we of the fourth state of matter, appearance around the solar to identify in the presence of you, nor your friend moves, of scientific thinking dawned can say that the Sun takes care which is plasma (a fluid in disc during a total solar the bright photosphere, just like yet the ball is transferred from upon us, we, instead of of the ABCs of our life, that we which the constituent particles eclipse), the transition region the way it is difficult to discern you to your friend. This is the taming, started to understand are too busy to care. are charged). This makes the and the corona (the Latin word the glow of a swarm of fireflies process of radiation. On the nature, realizing ourselves as a Sun a sphere of surprises for crown, named due to its around floodlights in a cricket other hand, if you are not sure veritable manifestation of the But thanks to the advancement that has been puzzling the crown-like appearance around stadium. The Sun generates its of the catching skills of your same entity. The Sun has been in our scientific understanding minds of scientists all over the solar disc during a total energy at its center through the friend, you can take the ball one of the biggest reasons for that we and the Sun are no the world. Just like our Earth solar eclipse.) Out of these process of nuclear fusion and is and walk up to your friend and the sustenance of life on our longer any cosmic strangers. has different layers of the layers, the photosphere is the at a temperature of around 15 hand over the ball to him. In planet. We have heard from Given the time, opportunity, atmosphere, so does the Sun. innermost, and the corona is million Kelvin. This generated this case, the transfer of the ball our school days that the Sun and expertise, we have found The Solar atmosphere, as we the outermost layer. It is the energy is transferred by first required you to move. This is is a blazing ball of fire, it is the that the Sun is not just a mere understand is comprised of the photosphere (the bright white radiation, and then convection the process of convection. From reason behind every bright ball of fire, but much more than photosphere (the term being disc that we see everyday), to the atmosphere of the Sun. the center of the Sun, as one 24 August 2020 August 2020 25 DOOT Indian Institute of Astrophysics Physics Concepts Physics Concepts Indian Institute of Astrophysics DOOT moves out, the temperature and being so, they often get the super flexible flux-tubes region is expelled from the attention. This is a situation aim of solar astrophysics. After decreases. This is what we twisted, stretched or sheared. get twisted, and sheared, and Sun at varying high speeds. where the question “WHEN” all, who among us cannot expect, as we move away When the magnetic field inside then they become flux-ropes (a This ejected magnetic structure surpasses by large the question sympathize that we long to from a fireplace, we feel lesser these flux-tubes increases, structure roughly resembling is highly energetic as they “IF” for their importance and be here for a reason, for a warmth with increasing they are pushed upwards, a twisted towel when we drain result from a series of multiple implications. But we must broader goal to understand distance from it. But the Sun finally emerging out of the out the water from it). re-connection that releases understand that we don’t look better, the intricate knots that defies this strong intuition photosphere (but still staying a huge amount of thermal at things as it is, but we look at tie the stardust (us) to the star of ours, and shows a sudden connected to the Sun). These If you are wondering at and electromagnetic energy them as it was, because light (our Sun), to preserve this increase in its temperature in regions through which these these striking and unusual in a very short span of time. (and hence the information) ‘pale blue dot’, to realize the its outermost layers, resulting tubes emerge out are seen features the Sun shows, then They are called Coronal Mass takes a finite time to travel. universe within us, and most in a coronal temperature of a as dark spots on the solar hold on a little more, as the Ejections (CMEs). These ejected What we see has already importantly to understand few millions of Kelvin, while disk (photosphere). They are best is always reserved for materials travel from the Sun happened and, what might THE SIGNIFICANCE OF the Photosphere is only at termed Sunspots. Despite being the last, and I being no Sun, into the outward space, and happen in the future is an THE INSIGNIFICANT US, IN around 6000 K. This is also dark spots, due to very high will surely comply with this hence in some cases, towards attempt to answer “WHEN”? LIVING WITH OUR STAR – known as the famous coronal magnetic field content, they notion. In our high school Earth too. And in such cases, As an attempt to answer these THE SUN. heating problem. Such change harbor the brightest of events physics, we have learnt that there is a potential chance of IFs and WHENs, there have of temperature, density and that occur at the Sun. These two magnetic lines of forces another reconnection between been several space and ground magnetic structure with cannot touch each other the magnetic lines of the CME missions to study the Sun from height is manifested in The Sun, apart from being such or intersect. But even that and the Earth’s own magnetic several countries. India is also different looks of the a sphere of surprises, is also a is possible at the Sun’s field lines, which leads to getting ready with our first- Sun as seen in different fascinating cosmic laboratory for upper atmospheres, in what are known as violent ever space mission to study wavelengths (see Figure astrophysicists, that offers visual the corona. It has been geomagnetic storms that can the Sun, ADITYA L1. ADITYA 1). evidences of several equations observed that when severely damage our daily life L1 will provide us with crucial that we find in books, equations two oppositely directed by creating power grid failures, information that might help Along with this, the Sun which are difficult to carry out in magnetic field lines come damaging satellites, and posing us to connect the ‘IF’ to the on its own harvests a any man-made laboratories. near each other, they get threat to astronauts in space. ‘WHEN’ and possibly unite magnetic forest in and re-connected, and this And despite the unprecedented them to a more profound around itself. And just as every emerging flux-tubes protrude results in a violent explosion advancement in technology, question ‘WHY’? forest has a forest canopy, the up to higher heights and thus (a solar flare, as Prof. Arnab such storms are a catastrophe magnetic forest of the Sun reach the upper atmospheres. Rai Choudhuri, quotes these as we are not yet ready for. The Sun, apart from being also has a canopy, with an But, as mentioned earlier, the “signs of cosmic illness”, which such a sphere of surprises, additional fascination that Sun is no solid body, and hence the Sun tries to get rid of) that So, the situation is twofold. is also a fascinating cosmic the structure and appearance it does not care for the laws produces bright emissions in Firstly, ‘IF’ a solar flare occurs, laboratory for astrophysicists, of this canopy changes with that govern the dynamics of different wavelength regions of what is the probability of a that offers visual evidence of height. The magnetic field lines any rigid body (say an iron our electromagnetic spectrum CME ejecting out of it, and several equations that we find which create this magnetic ball). Thus, as the Sun rotates (radio, extreme ultraviolet, traveling towards Earth? And in books, equations which forest are highly dynamic in around its own axis, different X-rays, Gamma rays etc). secondly, ‘IF’ a CME does are difficult to carry out in nature. A set of such densely points on the Sun rotates with Things don’t stop here too. For travel towards Earth, ‘WHEN’ any man-made laboratories. Satabdwa Majumdar is a Senior packed magnetic field lines different speeds, and hence very energetic explosions, a will it reach Earth? It is a To understand nature is Research Fellow at IIA and he often form what is known as there is a relative motion part of the mass contained and situation of low probability, the aim of physics, and to works on kinematics of Coronal a flux-tube. These imaginary between adjacent regions on constrained by the magnetic but of high consequences, understand the Sun and the Mass Ejections in inner corona [email protected] tubes are highly flexible, the surface. As a consequence, forest in and around that thus demanding undivided Sun-Earth connection, is the

26 August 2020 August 2020 27 Creative Corner Indian Institute of Astrophysics DOOT Location: Bangalore Date: 15th August 2020 August 2020 Time: 20:00 IST Oh... Wind....

Suman Saha Senior Research Fellow

Sitting at the windows seat in the swift highway car, Feeling something blowing in stretching hands from the far...

Oh tell me who made you so beautiful, so soothing, How could be a molecular vibration so astonishing, breathtaking...

You come in juggling my hair It feels like someone so dear Someone who loves me too deep Someone who clinches my fear... Copyright © 2020 Heavens-Above.com * Everyday stars will rise 4 minutes earlier than previous day And whenever I try to ask you Watch out for when’s the first that I found you You seem like there forever August 11, 12 - Perseid’s Meteor Shower Always with me, nothing’s new... The Perseid’s is one of the best meteor showers to observe, producing up to 60 meteors per hour at its peak. It is produced by comet Swift-Tuttle, which was discovered in 1862. The With you howling in so light Perseid’s are famous for producing a large number of bright meteors. The shower runs annually from July 17 to August 24. It peaks this year on the night of the 11th and morning of the 12th. I can forget all the griefs behind The second quarter moon will block out some of the fainter meteors this year, but the Perseid’s My heart goes on flying new heights are so bright and numerous that it should still be a good show. Best viewing will be from a Dazzling dreams, dancing mind… dark location after midnight. Meteors will radiate from the constellation Perseus, but can appear anywhere in the sky. August 13 - Venus at Greatest Western Elongation The planet Venus reaches greatest western elongation of 45.8 degrees from the Sun. This is the best time to view Venus since it will be at its highest point above the horizon in the morning sky. Look for the bright planet in the eastern sky before sunrise.

August 2020 29 DOOT Indian Institute of Astrophysics Review Review Indian Institute of Astrophysics DOOT in visible color), which are above the Earth’s atmosphere. black bodies, the physical bright in optical wavelengths We took the observations of parameters of a star, such as outshining the young BSSs. the cluster using Ultraviolet effective temperature and Thus, identifying the BSSs in Imaging Telescope (UVIT) radius, remain hidden in its Globular clusters is not an easy onboard AstroSat, India’s spectrum. Therefore, we have task. It is just like counting a first multi-wavelength space obtained the spectrum of one bunch of fireflies (BSSs) with observatory, launched on 28 BSS candidate, NH 84 (named a huge light bulb (red giant September 2015 by Indian Space after the first discoverer: Detection of a dead companion to a Vampire star stars) in front. The brightness Research Organisation (ISRO). Nemec and Harris) located of a light bulb dominates over in the outskirts of the cluster in the Globular Cluster of our Galaxy that of the fireflies, making With the help of the UVIT using Gemini multi-object it difficult to distinguish the data, we have identified the spectrograph mounted on Snehalata Sahu fireflies from the light bulb possible BSS candidates in the Gemini North Telescope in appropriately. Thus, to Hawaii, USA. We were identify the fireflies, we Our study provides the observational unable to obtain the must switch off the light evidence of a vampire star caught with spectra of the rest of the bulb. Similarly, to detect a dead companion in a binary system BSSs as the telescope the BSSs, we need to in the outskirts of cluster NGC 5466 cannot resolve these stars, switch from the optical which lie in the crowded Have you ever heard of a of the cluster (10-13 billion types of stars are called the using the Indian UV Space Telescope to Ultra-Violet (UV) regions near the center of vampire-like star existing in years), these stars should Vampire-like stars. wavelengths, as BSSs are the spherical house. our Universe? If not, then you have been dead now, unlike brighter in UV. are missing the story of one the other low-mass old stars Here’s the story of how our Far-UV (< 2000 Angstroms) By spectrum analysis, we of the most exciting types of which still have enough food team at the Indian Institute Generally, astronomers use filters in the cluster NGC 5466 found the radius of the BSS NH stars, known as “Blue Straggler to survive i.e., hydrogen fuel of Astrophysics Bengaluru filters mounted on the detectors and checked whether they are 84 to be 1.44 times the solar Stars” (BSSs). They are called to burn. It suggests that the has caught one such vampire in the telescopes to study the real members of the old GC radius, and the temperature so because they appear blue BSSs somehow managed to star with its dead companion the properties of stars. The house or not. One of the criteria around 8000 Kelvin (K). in color and straggle or lag get the extra food (hydrogen) hiding in Globular Cluster advantage of a filter is that it for being the actual member of This suggests that the BSS is in age behind their ancient to remain young and prevent NGC 5466, which is located in allows the light of a particular this ancient family is that they hotter than the Sun with peak neighbors, which are already themselves from dying soon. our galaxy in the constellation wavelength band to pass should all move together in emission lying at the bluer evolved off and dead now. After monitoring these stars Boötes. This work was done through, and bypass the rest. space. The true members were side of visible wavelengths. Its These stars were silently hiding with Space and ground in collaboration with a group It is similar to a tea filter that selected using the data from behavior in UV is unknown in a spherical house consisting telescopes, the astronomers of foreign scientists in Canada separates the tea leaves from the Gaia spacecraft of European as the obtained spectrum of only old stars, known as found observational evidence and the USA. the water. UV filters suit best to Southern Observatory (ESO) that covers only the visible and Globular Clusters (GCs), before that some of these stars are identify the BSSs and other hot consistently tracks the motions near-infrared part of the total they were first discovered in not single; rather, they exist To look for the vampire stars, stars. We are aware that the UV of these stars in space for years. radiation emitted by the BSS. 1953. The discovery of BSSs in binaries. These results we first need to identify the observations cannot be carried It is the first time we have Exploring the UV region can led the astronomers to concern revealed that the BSSs possible candidates from the out through ground telescopes observed these stars in the Far- provide essential clues about how come such an old age might have gained the extra millions of old stars present in because Earth’s atmosphere UV domain and identified 14 the nature of the BSS. The idea home i.e., GC, harbor these fuel by sucking mass from the house. GC house contains blocks the UV light. Thus, to BSS members. is straightforward. If the BSS is young BSSs? Given their mass their companion star. This a large population of cool stars observe in UV filters, we need a single star, its emission in the (1.2-1.4 times the mass of phenomenon is analogous to a such as red giants (as they are to put our telescopes in space If we approximate stars as entire wavelength range of the the Sun) and the current age vampire-like event, hence these large and appear red

30 August 2020 August 2020 31 DOOT Indian Institute of Astrophysics Review Experience Indian Institute of Astrophysics DOOT

Meeting the Milkyway.....

Cartoon diagram depicting the story of the search of a vampire star and its dead companion (Credits: Snehalata Sahu). Chayan Mondal Photo credit: Ms Ramya Manjunath and others spectrum, including the UV photosphere temperature, and cluster NGC 5466 using the wavelengths, should match the radius is around 2 percent Indian UV Space Telescope. with a star of temperature 8000 of that of the Sun. It suggests The UV observations have K. If it didn’t, then there are that the companion is a white helped in finding the reason Seeing the night sky filled to your imagination of the observatories and see the other mechanisms contributing dwarf (WD). They are called so behind the early death of the with uncountable stars sky. Without an exception, it telescopes and the night sky. to the UV emission causing a because they appear white and companion star. In the past, the always amazes the one who happened so one day. Thanks to the professors and deviation. Thus, to sample the are small in size. The WDs are BSS was like an old member loves to see it. The journey of a group of senior students, UV region of the spectrum, the end stages of the evolution of the GC house, but later exploring this vast universe It was during the August who took all the hurdles we took the help of the UV of stars having specific mass. it underwent mass transfer begins its first footstep with of 2015, when I had just to organize a workshop, observations carried out in four They don’t have enough mass from a giant companion, the introduction of the night completed the first year at which made our journey to UV filters of UVIT. Checking to undergo further nuclear appearing younger and more sky. The experience Kodaikanal possible. the slope of the spectrum in fusion and are thus dead. They massive in the present state. of observing it starts “ It was cold and dark and I couldn’t As the place is a the UV region, we found that can’t be detected easily as they UV study of more such BSSs adding the colors to the remember how long we had talked hill station and it the BSS shows excess emission are extremely faint in visible in the future can provide a canvas of imagination. with the Milkyway. The colors of was the month of in the UV wavelength region, wavelengths. But being hotter, better understanding of their The more you get to see, imagination, which were painted new on August, the weather which is not expected from a their peak emission lies in Far formation mechanisms in the more you fall in love that night, will remain bright forever.” was expected to single star of temperature 8000 UV wavelengths. We illustrate the clusters. The results are with it. For the same be cold. We were K. Further analysis suggested the result in the cartoon above. published in the Astrophysical reason, the opportunity supposed to leave that the excess UV emission can Journal (Sahu et al. 2019). to work as a researcher at IIA IIA as a research student. We early in the morning from be explained by invoking the Our study provides the comes with a dream to witness got an opportunity to visit Bangalore. So, all the planning presence of a hot companion. observational evidence of a Snehalata Sahu is a Post- the beauty of the night sky the Kodaikanal Observatory. and preparations were done The hot companion’s vampire star caught with a doctoral Researcher at IIA. She from the observatories. These It was just in time as my overnight. The excitement of temperature was 32000 K, dead companion in a binary works on stellar populations in globular clusters. are among the few places, batchmates and I were traveling itself was huge, as we which is five times the solar system in the outskirts of where you can get the closest very much eager to visit the were told that it would take

32 August 2020 August 2020 33 Physics Concepts Indian Institute of Astrophysics DOOT Indian Institute of Astrophysics Experience DOOT the whole day to reach the house after our dinner and will remain bright forever. It observatory and there could saw the sky on the way. It was was difficult to believe that be vomiting due to the up-hill spectacular and exquisite and we sleep every night under ride. We started our journey probably beyond any proper the same sky, but hardly get from the campus on board a adjective. Most of us stopped a chance to see it the way we bus and reached Kodaikanal walking and just stared at the saw it that night. The sunrise after evening. Right from sky for a few minutes. We just next morning made me feel the moment we reached, I enjoyed that moment together like I just came out of a dream, “Errors are beautiful and Gaussian” started feeling the essence of by filling our heart with similar which I was living for so long. an astronomical observatory pleasures. Before we came to We came back to Bangalore Really? so far I have imagined. The the observatory, we were told next Sunday, but it took almost location, the weather, nature, that there could be bison inside a week to get back to the Soumya Sengupta and the campus, all together the campus and we must be rhythm of the city life again. I made the best impact on me as careful during night. As a could feel that the sky without a researcher. Those three days result, many of us decided to the Milkyway is so much of our stay at Kodai are among return to the guest house after empty. Since then, I have had a the best times of my journey a while. But, the eagerness to few more opportunities to see at IIA. We enjoyed every see the unveiled beauty again, the Milkyway and every time second with new learnings and took some of us back there. We it has amazed me with new experiences. There are many had two binoculars and this surprises and happinesses. But memories to be remembered time we took them with us. our meeting at Kodaikanal will Gaussian or Normal forever from that visit. Apart Some of the seniors arranged remain special forever. Distribution is the most from the lectures and friendly their camera to capture common of all the probability discussions, we could archive the beautiful Milkyway. I, distributions in a sense that plenty of memories in our together with my friends, the heights of the boys in a natural hard drive, which took the binoculars and lied classroom, the errors in any will never be erased until it on the ground for a long time experiments, or the probability is crashed. Walking through to witness every bit of the of acceptance of your proposal the beautiful campus, visiting unveiled eternal beauty. We (in your company or in love the nearby sites, dinner with could see a few star clusters as affairs) all follow the Gaussian a bonfire and music, boating well, which we had only seen distribution. De Moivre in the Kodai lake - everything in the textbooks. Moreover, I first reported the Gaussian seems so much alive, even was amazed by the thought distribution and sir Gauss today. Among all those that we know so little of what worked for its development. Figure 1: A Gaussian distribution function memories, the one which will we can see and we see so little The Gaussian distribution where, µ is the mean value or Here in figure 1, you can see certainly be there forever is of what actually is there in function has the following the expectation value of the the bell-shaped structure of the of seeing the Milkyway for the sky. It was cold and dark mathematical form, probability distribution i.e. Gaussian distribution function. the first time in my life. I still and I couldn’t remember the probability of finding the The probability is clearly don’t have the proper words how long we had talked with Chayan Mondal is a Post-doctoral variable x in this distribution maximum at µ = 2. to express the feelings of that the Milkyway. The colors Researcher at IIA and works is maximum at µ and σ is the first experience. That night, we of imagination, which were in the field of extragalactic star formation standard deviation of the were coming back to the guest painted new on that night, [email protected] distribution. 34 August 2020 August 2020 35 DOOT Indian Institute of Astrophysics Physics Concepts Physics Concepts Indian Institute of Astrophysics DOOT Now I will show and when all are ’head’ then sums. If we replace that “+1” proportional to N for constant practically how we can S=10 (maximum). Therefore, or “-1” steps by some random M. get Gaussian distribution for N number of tosses, the numbers between -1 to 1 then in an experiment: minimum value of the sum the diagram will change its Whatever be the value of M Suppose, I toss an unbiased of assigned values is -N and shape as Figure (2b). In Figure (i.e. the number of coins) or coin N number of times. As the maximum is N while the (2b) we can observe that the N, the shape of the Gaussian the coin is unbiased, we expect assigned values are ±1. maximum and minimum of remains the same. Look how there is a high probability of the summed values changes beautiful the errors are! They getting an equal number of Now we can think about M from ±N. This is because the are always symmetric on head and tail, provided N is which is the number of coins assigned random numbers are both sides from the mean, large. How large? Suppose to do the experiment. If we in between -1 and 1. irrespective of where the mean N=10. Then obviously the do this tossing with really is. In this note, I have discussed probability of getting an equal large (how large? Suppose Let’s progress further in this a little about the starting point number of heads and tails is M=10,000) number of coins experiment. We can now fix the of a Gaussian distribution. You and plot the histogram of those number of coins (i.e. M=10,000) can think more, play more, and very less. Now if we plot it in Figure 3: Histogram for various values of N a graph and check how many summed values we will get the and increase the value of N we will get sharper and sharper will increase. So, if we increase have more fun. heads or tails are there for N Gaussian. Now, it’s time to N infinitely the Gaussian will number of tosses, let’s assign conclude this experiment become a delta function (Ohh ”+1” with head and ”-1” with and give some predictions really! You can think about it.) a tail. So, after N number with logical intuition. If we One more thing to note is that Soumya Sengupta is a Senior of tosses if we add all these increase the number of tosses the height of the Gaussian Research Fellow at IIA and he works on Modelling of Exoplanet assigned values then the sum (i.e. N) with a fixed number is directly proportional to N atmosphere should be equal to zero (as the of coins (i.e. M fixed), then the (i.e. the number of tossing) [email protected] probability of getting Head and (a) With ±1 assigned value sharpness of the histogram while the flatness is inversely Tail is equal). As we expect the 2 Here the delta function distribution means that the probability is fixed at a particular point. sum of this assigned value is zero so technically the mean or Expectation value for this experiment is zero.

Now if we perform this same experiment for M number (b) With random assigned value of coins then the sum will Figure 2: Histogram plot of the sum of assigned values of the coin tossing not be always equal to zero experiment at N=10 and M=10,000. See, it takes a Gaussian shape. (obviously, right?). So, what will be the minimum and following graphs. from 10 to 100, 1000, and so on. maximum value of this sum From figure (2a) it is clear Then the histogram will change for N=10 number of tosses? If that when M is large (10,000) as shown in figure 3. Thus, all outcomes are ’tail’ then the then the histogram looks like by increasing the number of Calligraphy artist: Radhika Dharmadhikari sum S=-10 (which is minimum) a Gaussian. But the bar-like tossing in this experiment structure is due to the integer Int. MTech-PhD

1 Unbiased coin: For an unbiased coin if the probability of getting” Head” or” Tail” is exactly same. 36 August 2020 August 2020 37 DOOT Indian Institute of Astrophysics IIA Stories IIA Stories Indian Institute of Astrophysics DOOT

Equipment used: Sony A7s2 Rokinon 14 mm @f/4

Eclipse image: Exp 1/4000s x 80 subs, ISO 400 with ND filter was used for the eclipse timeline.

Foreground without filter Exp 1/40 sec ISO 200

All the eclipse images were Photo credit: Indian Space Research Organisation (ISRO) opened as layers in Photoshop and blended using the light mode. First Light with UVIT Photo credit: Dorje Angchuk Timeline of Eclipse over Indian Astronomical Amit Kumar

Observatory I would like to share the was quite tiring and full-of- months. Generally, the UVIT Dorje Angchuk heart holding experience of patience work to check an operations used to happen in my first Space Project, UVIT instrument on-board and it the eclipse part of the orbit and Solar Eclipse as it happened over Himalayan provided an interval of 30 sec between each on ASTROSAT. It was 30th becomes more critical when it used to be in the evening at Chandra Telescope (HCT) at Indian eclipse shot but for the final image I choose November 2015. We had it comes in line-of-sight Bangalore with the line-of-sight Astronomical Observatory. This being my first each exposure which was separated with an finished all the major checks on connection with the ground of connectivity. solar eclipse was quite an experience since we equal interval of 150 sec. A few passing clouds UVIT payload when its doors station only for 10 minutes were providing live feed of the eclipse too. I dimmed the eclipse after the maximum. were closed. Just to remind in an orbit of 90 minutes. We During the daytime on 30th have always been in awe of the eclipse with the readers, ASTROSAT was used to prepare commands November, the FUV and NUV the landscape and this time it was technically During Annular solar eclipse photography it is launched on 29th September during the Spacecraft invisible doors opened in orbit numbers difficult as the elevation of the sun was too high. always recommended to take the foreground 2015 from ISRO space center period, verify it 2-3 times; 935 and 936 respectively. So I had to use the wide angle lens and test the at dawn or dusk, so that the harsh light during in Sriharikota(SHAR). Since and then clear it for upload Now, the UVIT and the team setup a day earlier. My initial plan was to use day time is avoided to merge the surroundings. then, the UVIT team had been in the next visible period of was ready to do its first ever 20 mm but had to settle for 14 mm since the To avoid removing the filter and disturbing engaged with the on-board the spacecraft and verify the on-board observation. The dome was not coming in the frame. This also the setup, my tripod was set up the previous checks of the payload, along operation in the next orbit spacecraft was manoeuvred to meant making a new filter quickly as different day. I drove to the HCT at 4:30 AM to take the with the Mission Operation when we receive the data. This the source NGC 188 and all the lenses have different diameter. Although I have foreground and hence the resultant image. team at ISTRAC-ISRO. It process was continued for 2 command codes with required 38 August 2020 August 2020 39 DOOT Indian Institute of Astrophysics IIA Stories Location: Bangalore filter position were made changed, and we could start the science data of the previous Date: 15th September 2020 ready. It was evening around again in the next orbit. orbit 939, so that we could September 2020 Time: 20:00 IST 6:30 PM and the spacecraft was complete the first observation in orbit 938. As soon as the With all precautions in place, of UVIT. It was around 11:00 spacecraft came into visibility, we started with the same pm and the team was very the commands were uploaded, excitement again, but with little curious and waiting for a quick as it was visible only for 10-15 fear in heart. It was in orbit look at the image with fingers mins. Only a short observation 939 of the spacecraft and all crossed. As soon as the data was planned only for the VIS the commands were uploaded download started and a quick channel of UVIT (UVIT has 3 again. This time around, all look image appeared on the big imaging channels; FUV, NUV the things went alright. Filter screen at MOX, the whole team and VIS). entered a big moment “...it was a moment of satisfaction and self- of joy and happiness Even if all the pride. My eyes were filled with tears...” after seeing the NGC care was taken 188 observed with in command UVIT. verification, the filter wheel of was positioned correctly and the VIS channel was positioned observation continued as For me, as I was involved at the wrong place during the planned. In this orbit, we were more in electronics hardware first observation. I was sitting able to download the science integration and testing till its on a terminal to verify the data of the previous orbit 938. on-board operation, it was a telemetry of the VIS channel After having a quick look at the moment of satisfaction and and I noticed this wrong filter image of VIS, a big bright patch self-pride. My eyes were filled position and in excitement, I on the screen confirmed a BOD. with tears after seeing the first had commanded the operation Now, everyone was waiting for image. I was sitting on the team at MOX-ISRO for the the next orbit 940 to download console and wishes started Copyright © 2020 Heavens-Above.com movement of the filter wheel pouring from all around. * Everyday stars will rise 4 minutes earlier than previous day to the required position. In Then ISRO Chairman Dr this process, the FW started Kiran Kumar also called the Watch out for rotating and because of a UVIT PM Prof. S N Tandon bright source in the Field of and congratulated the whole September 11 - Neptune at Opposition View, the on-board Bright team. The blue giant planet will be at its closest approach to Earth and its face will be fully illuminated Object Detector (BOD) logic by the Sun. It will be brighter than any other time of the year and will be visible all night long. This is the best time to view and photograph Neptune. Due to its extreme distance from Earth, it of UVIT got triggered and will only appear as a tiny blue dot in all but the most powerful telescopes. it went to Power OFF state immediately. It was a big setback for the team and September 22 - September Equinox the problem identification Photo credit: Indian Space The September equinox occurs at 13:30 UTC. The Sun will shine directly on the equator and there started immediately. We Research Organisation (ISRO) will be nearly equal amounts of day and night throughout the world. This is also the first day of fall (autumnal equinox) in the Northern Hemisphere and the first day of spring (vernal equinox) narrowed down that filter Amit Kumar is an Engineer-E in the Southern Hemisphere. wheel position and the image at IIA, who is associated with parameter set for VIS, to be the ASTROSAT project.

40 August 2020 Indian Institute of Astrophysics DOOT Indian Institute of Astrophysics Creative Corner Review DOOT The Universe, An Occult

Bhoomika Senior Research Fellow

Every time when I looked up into the Sky Like a child, many questions seemed to fly I always found it the most enigmatic and bright Its unimaginable beauty amazed me time to time Charm of twinkling stars made me curious every time Testing Theoretical Bar Formation Criterion I used to pray to the falling star many times But always wondered, where it is going to dive I was ever thrilled where the lovely moon hides Sandeep Kataria The adorable moon becomes more mesmerize When it comes between the earth and sunshine On beautiful Mars and Venus, how will be the life How never gets out of the Black hole that goes inside Bars are ubiquitous features in conducted by Erik Holmberg in bar type instabilities if they are Having learned today all these meager puzzles the disk galaxies. Observations 1941 with the help of bulbs and kinematically cooler or having But Universe is far beyond than my visions show that around 2/3 of the photocells, to find the forces lower velocity dispersion in The Universe is full of allure and incredible sights disk galaxies in the observable among stars in an interacting the stars (i.e. ratio of rotational The Big Bang Theory, where the Universe derived universe (optical and infrared) galaxies system. Here, each kinetic energy to potential Where galaxies were formed in the billions have a bar in their central star particle is provided with a energy < 0.14). Later on, there In each galaxy, stars were framed in trillions region. Bars are thought to be bulb and photocell. Photocell were several studies using Every star in a trillion stars has its own covert formed as a result of global captures the inverse square N-body simulations that talked Every star has its own planets like our Sun instability in the disk, which nature of gravity as it collects about bulge, disk and dark Star lives its life and the star even dies traps eccentric orbits In this study, we came up with a matter halo properties When a star dies, the new structures thrive of the stars in the criterion which says that if the ratio affecting the formation of And Neutron Star or Black hole will arise bar potential. As of the radial force due to bulge and bars. In our recent study, Black hole, Neutron star play around each-other the bar formation radial force due to Galaxy at disk scale we have revisited the And create ripples in the space-time Universe is a complex length exceeds 0.35, galaxy disk will effect of bulges on the The more facts solved the more puzzling becomes phenomenon be stable against bar instability. bar formation with the The star born before the Big-bang eruption involving nonlinear motivation to quantify the Makes puzzles of the Universe more muddled dynamics, there effect of bulge mass as well is very little analytical light from the other bulbs as bulge concentration on the Even today when I look into the Sky understanding of these. For (other star particles in this case) bar formation in disk galaxies. My childhood memories start to reignite the past several decades, and computes forces to predict In this study, we came up with When I witnessed the Milkyway in frightful nights bar types of instabilities are it’s motion. a criterion which says that if But the Universe is as thrilling even today to me mostly studied with N-body the ratio of the radial force due The Universe is around me, is way ahead of me simulations. Despite the A pioneering study by Ostriker to bulge and radial force due And brimming with mysteries and only riddles absence of modern computers, and Peebles in 1973 has shown to galaxy at disk scale length the first N-body study was that galaxy disks are prone to exceeds 0.35 (Kataria & Das Photo credit: Anand M N 42 August 2020 August 2020 43 DOOT Indian Institute of Astrophysics Review IIA Stories Indian Institute of Astrophysics DOOT

The shining eyes

Anand M N Photo credit: HST Barred galaxy NGC1300 with star formation at the edges of bars as well along the leading edges of spirals can be seen)

2018), galaxy disk will be calculated the criterion values of bulges etc. We have also It was a school project on lunar In that summer, I got my first an hour explaining the stable against bar instability. for disk galaxies using S4G checked our criterion for observation that motivated me, opportunity to visit the Vainu instruments and clarifying This criterion basically takes data. We were able to obtain unbarred galaxies and we a 11th standard boy, to serious Bappu Observatory with Dr. our doubts. On this trip, Dr. into account the effect of bulge bulge mass, disk scale length found that our criterion is a star gazing. Till then, I used Parihar and Dr. Tarun Sharma. Parihar’s family was there mass and concentration on and rotation curves for all the necessary condition for bar to see the twinkling stars, but That was my first ever visit with us too. After the evening the stellar dispersion in the sample galaxies. We have formation but not the sufficient not too keen about knowing to an observatory and those tea, we used to go for a walk disk. As the bulge mass or used both barred and unbarred one. This is because there them. That project gave me an were the most exciting days outside the campus. We would concentration increases in the galaxies for this study with a are other processes that can opportunity to meet amateur of my life. The trip was for the return by sunset and keep the central region of the disk, it total of 158 galaxies. We found increase the velocity dispersion astronomers and science testing of Extinction Monitor instruments ready for night makes the disk kinematically that more than 92 % of barred in disk galaxies, like satellite enthusiasts outside my school. developed by Dr. Tarun as a observations. We had arranged hotter or tends to make it galaxies in our sample follow interactions, galaxies passing part of his M.Tech thesis work. the instruments on top of the stable against bar instability. the bar formation criterion. through clusters etc. With continued motivation We stayed at VBO nearly for a administration building in such One of the advantages with This result clearly indicates and encouragement from my week and got a chance to visit a way that we can see the Pole this theoretical criterion is that the disk is prone to bar parents, teachers and those the Vainu Bappu Telescope, star for easy alignment. Once that it can be calculated with instability only for certain amateurs, my interest became a then-largest telescope of the instrument setup is done, observable parameters of bulge mass and concentration passion and hobby. I became a India. The rising platform we would rush for dinner. galaxies, i.e. bulge mass, disk ranges as captured by regular face in local star parties and seeing the big 90” mirror scale length and rotation curve theoretical bar formation and telescope making sessions. of VBT was so exciting. Dr . After dinner, our observations of galaxies etc. criterion. This criterion is valid Slowly, I started assisting those Parihar explained the telescope and testing would start. Since for isolated evolution of disk Sandeep is a Post-doctoral sessions. Seven years later, after operation and took us to the we didn’t have any polar scope With the motivation to test the galaxies, where the velocity Researcher at IIA. His area completing post-graduation in Echelle Spectrograph. in the instruments, alignment of research includes galactic above mentioned theoretical dispersion of disk changes dynamics and large scale Electronics, I joined the Indian Every day, he would take was difficult on the first criterion in the current through internal dynamics structures in the universe using Institute of Astrophysics. I was us for a walk to one of the day. We started with rough observational study, we have of the galaxy, i.e. presence N-body/SPH simulations. so excited and thrilled. telescopes and spend nearly alignment seeing the pole star Photo credit: Anand M N 44 August 2020 August 2020 45 DOOT Indian Institute of Astrophysics IIA Stories IIA Stories Indian Institute of Astrophysics DOOT and improved it with drift The villagers had good During our walk, we had volunteered sky watching the kids looking at the eclipsed which again led to Mars. Then, alignment. Instrument testing relationships and respect for some soft drinks and snacks sessions at Koramangala Sun, the 84 year old grandma, one of our team members, who would extend up to the early the observatory staff. I was the from one of the shops. There campus. Now, I am at the who was reluctant and asking was pursuing his PhD, was morning. The next day would only South Indian in our team, we met an old man. He must Kodaikanal Solar Observatory. the kids to get inside, came worried that the topic could only start by noon. Depending so was the translator for all have been around 70 years Yearly, thousands of visitors out and saw the eclipse for the turn out to be controversial. upon the time of our wake up, conversations. old. We asked him about the come to our museum. School first time ever in her life. That However, reason prevailed, we would go for a telescope observatory and his experience and college students visit our excited her and she stayed as we realized that it was our visit before or after of seeing the Moon observatory facilities too. I outside till the end of the primary responsibility to help lunch. Tarun would be “It was so close. I could even touch it”. through the telescope. like to interact with small kids eclipse. clear superstitions about the analyzing last night’s He was so excited and rather than the elders. They are negative beliefs surrounding data in between. said “It was so close. I curious and ask many innocent There were some experiences Mars. I feel it is up to us to VBO has a good history of could even touch it”. His eyes questions too. too during the outreach play a significant role through One day our evening walk public outreach and every were shining like a star. It has programs which triggered our programs to reach out was to a nearby village. It Saturday, the public can come been nearly 8 years since then. On 26th December 2019, there my sense of responsibility as to people and rid them of was a small village with a and experience the night sky Still, I remember those shining was an annular solar eclipse. a member of the society I am superstitions that might few families and a couple of through a small telescope, eyes. That was one of the best I had sent eclipse glasses to living in. During one of the negatively impact their lives. If shops for their basic needs. installed in the lawn near the experiences in my life, teaching my hometown as well. My outreach meetings at Bhaskara we will not do it, who else will? For bigger purchases and administration building. VBO me the importance of outreach cousin took a couple of those Guest House, prior to a school medical facilities, they would staff will be explaining about programs. to her family. They are from an visit near the institute, the have to visit the nearest the objects they see through the orthodox Brahmin family, who discussion was on the lecture Anand is a Junior Research Assistant at Kodaikanal Solar town, Alangayam. Now the telescope, mainly planets and Later, I became part of the IIA consider eclipses as bad omen topic of the following day, Observatory (IIA). He is interested village is developed and the the Moon. outreach team and visited a and stay indoor reciting the Solar System. The discussion in astrophotography. population has also increased. couple of schools and mantras. But this time, seeing turned towards mythologies, www.facebook.com/amnphotos Photo credit: Prasanna Deshmukh Photo credit: This image is sketched and gifted to KSO, IIA by Kamalesh 46 August 2020 August 2020 47 Indian Institute of Astrophysics DOOT Indian Institute of Astrophysics Creative Corner Physics Concepts DOOT

Zeeman Effect

Raveena

The Zeeman effect was first by eliminating density or discovered by the Dutch temperature variations, but he Artist: Snehalata Sahu When a magnetic field Post-Doctoral Researcher physicist Pieter Zeeman in 1896 observed the same widening (B) is applied along, when he placed the flame of of the spectral lines. He was say, z-axis work is a Bunsen burner between the finally convinced that it was done on the dipole by poles of an electromagnet and the effect of the magnetic field the torque or force that held a piece of asbestos covered that affected the light radiated acts on it due to the with common salt in the by the flame and resulted in applied magnetic field, the widening or splitting of the Annular Solar Eclipse December 2019 to orient it along the sodium lines. H. A. Lorentz, Images from the H-Alpha Telescope at Kodaikanal Solar Observatory Photo credit: Prabhu Ramkumar same direction as B. who was Zeeman’s mentor as 26th December 2019 witnessed one of the best Solar eclipses of well as collaborator, developed the decade in South India. Many a theory of electromagnetic Effect” for which Pieter programs were arranged all around, Figure 1 including the field stations of IIA. phenomena that clearly Zeeman won the Nobel prize Thousands including eminent explained the emission of light in Physics along with H. A. astrophotographers gathered at flame. After the electromagnet in this way. Thus, it was the Lorentz in 1902. Kodaikanal Solar Observatory. A team lead by Mr. Parthiban visited was turned on, he observed discovery of the “Zeeman the school where he studied at that the two D-lines of the Now, in order to understand Doddampalam, gave lectures and demonstrated the telescope to the sodium spectrum were clearly the Zeeman effect, we can Greatest Eclipse from Spectro, KSO students. Mr. D. V. S. Phanindra and widened. He thought that this Photo credit: Mr. Kumaravel start with the electronic Mr. Prasanna Deshmukh from IIA broadening of the spectral lines configuration of an atom. In Bangalore and Mr. Anand M N from KSO accompanied him. Dr. Ebenezer might be due to an increase an atom, the electrons occupy IIA Team at Govt. Hr. Sec. School led the team at KSO. Live eclipse- in the density or temperature energy states (also known as Doddampalayam, Erode, Tamilnadu viewing through safety glasses and of the flame. He repeated the Figure 2 orbitals) around the nucleus Photo credit: Parthiban.D video streaming were arranged at KSO. experiment with other sources and each electron has its own Photo credit: Dr. Ebenezer 48 August 2020 August 2020 49 Indian Institute of Astrophysics DOOT Physics Concepts Creative Corner Indian Institute of Astrophysics DOOT magnetic dipole moment due these sub-levels are oriented resonance imaging (MRI) to its angular momentum and along different axes x, y, and in which radio-frequency More than me... charge. This dipole moment z. Hence different amounts of radiation is passed through the (μ) is directed perpendicular work need to be done to make patient and when the protons Suman Saha to the area (A) covered by the all the p-orbitals direct along (present in water molecules of Senior Research Fellow electron around the nucleus B. This orbital splitting can, the human body) get excited to (shown in Figure 1). Each therefore, be represented in higher energy states and again I’m shy the form of different energy relax off to the lower energy Still trying to be brave levels as shown in the Energy state, this energy is detected To walk again diagram (Figure 4). and measured in order to Out of my grave diagnose the suspected body I’m weak The Zeeman effect was first parts. Still trying to be strong Figure 3 applied to solar physics in And change all 1908 by George Ellery Hale, That I’ve done wrong one of the best known solar Cause I love you energy orbital (s, p, d, f etc.) astronomers, who observed the More than me... of an atom can be further split difference between two spectra And that’s the reality... into sub-levels according to the from a sunspot and this led to rule: (2l + 1), where l = 0 (for the discovery of the existence I’m a liar s), 1 (for p), 2 (2 for d) and so of strong magnetic fields on the But I’m telling the truth on. For a given l, these sub- Sun. Today, this effect is being Been so hard levels have the same energy I’m still learning to rewth (degenerate) in absence of It’s a war any magnetic field. When a And I’m fighting the way magnetic field (B) is applied Been so far along, say, z-axis (Figure 2), Still can hear what you say work is done on the dipole by Cause I love you the torque or force that acts on More than me... it due to the applied magnetic And that’s the reality... field, to orient it along the

same direction as B. Now the Figure 4 Tell me once splitting of the orbital occurs If you have anything in heart because the work done or used to create magnetograms Let me love you energy required to align each which show the variation of the Let me draw it in art sub-level along B is different magnetic field on the Sun. It I’ll be there for different sub-levels of the is also utilized in laser cooling For all the way you go same orbital. For example, techniques in which atomic Ask me anything 2p energy level has an orbital and molecular samples are I’ll never say no quantum number (l)= 1 and cooled down to near absolute Raveena is an Integrated M.Tech- Cause I love you PhD student at IIA and she works so the number of sub-levels zero. The Zeeman effect finds More than me... on Solar spectropolarimetry. it can have are (2l +1) = 3 (i.e., its application in the medical [email protected] And that’s the reality... px, py, pz in Figure 3). Now, field as well, such as magnetic

50 August 2020 August 2020 51 Indian Institute of Astrophysics DOOT Indian Institute of Astrophysics Experience Experience DOOT

Passo del Tonale The Story of a Winter School

Fazlu Rahman

The journey started around hurry. I got my Schengen VISA with Lombardy and is one

7 PM CET from the Trento approved only a few hours of the best skiing sites in the Photo credit: Fazlu Rahman station. The white Volvo bus before the flight. Forty hours of Alps. It is the beginning of updated details of the field. This is particularly The style of the school was interesting; the began ascending the curly travel, many sleepless nights the Christmas holidays and useful for masters and early PhD students, organizers designed it in such a way that routes and curvy paths, while and the first travel to a different we could see skiers in the to get to know the active topics of study and participants get the best out of it. Four sets of we were busy making new continent – attending the distant top. A few hotels, one design their research goals. I could say that our lectures in the morning, tutorial sessions in the friends. We were around school being exhausted would market store, skiing office and zestful organizers could properly convey that evening. Post-lunch session was free, giving fifty students, doing masters be of less worth. Thanks to some apartments, the village vibe of activism to us. participants the chance to explore the winter and PhD in different parts my planning, I got one whole is all set for a magical winter of Tonale – skiing, snowboarding, snow walks of the globe, came to attend Sunday to relax and explore the experience. Led by our highly The 2019 version was especially exciting for etc. For the working groups in the evening, we the 13th version of Tonale serene town of Trento, known energetic hosts, a few young me - one major discussion was about Cosmic were split into four groups – CMB, neutrino, Winter School on Cosmology. for sky-touching cathedrals postdocs working in different Microwave Background (CMB) polarization dark energy and perturbation theory. In our Being my first trip to Europe, and historical monuments in parts of Europe, we started and Galactic foregrounds which is closely CMB group, Mathieu asked us to work out everything was exhilarating the Alpine valley of Northern walking to the venue set up 5 related to my thesis. The speaker, Mathieu related problems and discussed topics not for me. Climbing 1800 m above Italy. After spending a pleasant min away from the hotel. Remazeilles from Jodrell Bank is very active in covered in the morning sessions. It was kept the sea-level for 90 minutes, evening on the banks of river this field and some of my works are based on highly interactive and the Q/A session went till the bus halted in front of Hotel Adige, I rushed to the station to Four days, hot topics and the sky-maps prepared by him. I found this as the dinner time. Adamello, our new home for join the team. a winter school in its exact the best opportunity to learn directly from him. the next few days in Passo form – this is all about the It went exactly as per the plan, Mathieu taught Post dinner sessions were for poster display del Tonale. Outside was -15 The misty morning of Monday Tonale winter school. With the me a lot of new things and shared his own and informal discussions. Speakers, postdocs centigrade and we all ran into welcomed us with the warmth theme - ‘Theory for observers, experience in dealing with CMB data pipelines. and students across the globe sharing their the hotel. of the Adamello Cappuccino. Observations for theorists’, the The other topics were also not of less exciting: exciting works and vivid research stories – Tonale in its white attire was winter school annually brings neutrino cosmology, non-linear perturbation what more can we expect from any school. The whole preparation for ready for its winter visitors. experts in various areas of theory and dark energy observations, and a Adding to the happiness, I could bag the best this European trip was in a Tonale pass connects Trentino cosmology to discuss the bunch of good speakers. 52 August 2020 August 2020 53 Indian Institute of Astrophysics DOOT Indian Institute of Astrophysics Experience Experience DOOT poster award and convey to a larger audience, And, it was the time to hasta la vista. Of course, the kind of works I am doing at IIA. Our the cosy accommodation and the yummy field is relatively new, we usually do not find Italian cuisines made the event unforgettable. people working in it. Thank you, Tonale!! You The regional dinner of Thursday night marked didn’t disappoint me at all. I got a few friends the official valediction of the program. Amidst engaging with the exact stuff I am studying the heavy snowfall of Friday morning, as our about. bus slowly started descending the hill, we My life at IIA were thankful for those wonderful days and Distinct sessions made this school unique. myself excited about the next week’s meeting at Sangeetha C R One informal post-dinner session was for the Munich. speakers and post-docs to tell us their life stories, what motivated them to pursue their career, their hurdles and success, inspiring the budding researchers. We had a CV feedback session on the last day. Students could interact with the experts – speakers and post-docs – showing our CV, collecting their suggestions on Fazlu Rahman is a Senior Research Fellow at IIA working in observational how to improve our academic records to apply cosmology. I joined the Indian Institute to prepare you to get over the feature is that you can’t have for positions and to present it perfectly. of Astrophysics (IIA) in 2010 initial awkwardness in the specialized courses in the area for PhD and had very little field. Of course, this may not be of your research. Also, when knowledge about research. true for all since not everyone we joined for PhD, each faculty Being a shy person, pursuing would have the same issues. could only have a maximum your dream in research is a bit In IIA, we get to choose our of two PhD students. This difficult, as you need to interact supervisor after we finish our restricted us from joining with people. But it is not an course work. That has both our field of interest and was impossible dream to have, and positive as well as negative strongly opposed by most I realized I needed to overcome sides. The positive side is of the students. Later, it was my weaknesses gradually. In that it gives us sufficient time changed to five students per a way, the course work during to interact with faculties in faculty, which I hope is still PhD helped me to get over IIA and choose a field after there. some of the difficulties. We had exploring all the current to give talks as an exam, which research activities done in the On the other hand, the facilities helped to overcome my stage institute. You can make a list provided by IIA were well fear to some extent. We had a of faculties in the field and equipped for research. We two-team group project where interact with them, their PhD were given a computer system we needed to discuss with students and senior students with internet as soon as we other students. We also had to of IIA. One needs to take the joined, which I think may not do a project which gave us a opinions of senior students, be the case everywhere. The brief look into what research but the final decision should library is well-populated with is basically about. I realized be yours alone since it is you lots of books and subscriptions over time that the structure of who will have to interact with to a variety of journals. It is also the course work was designed the supervisor. The negative connected with other research Photo credit: Tonale Winter school 2019 54 August 2020 August 2020 55 Indian Institute of Astrophysics DOOT Indian Institute of Astrophysics Experience Creative Corner DOOT institute libraries, so that if you times. can’t access a paper, you only need to write to the librarian A piece of advice to the current to get a copy of the paper and future IIA students through these connections. would be to enjoy life as it It is essential to enjoy The computing facilities were is. The stress of work will be life little by little, as and also wonderful when I was there throughout life. During when possible. It is a PhD student. Interacting PhD days, we want to have vital for our overall well- with seniors in the first year sufficient material for thesis, being. Spend half an will help understand the during post-doctoral days we hour to an hour a day facilities of IIA, which may need to keep publishing to for personal activities not be available in written get a job, and even after we like pursuing a hobby, format. IIA often had a lot of get a job, there will probably exercising or reading visitors during my PhD days, be some work-related stress. non-academic books. which led to a good amount Hence, it is essential to enjoy Maintain your health as of seminars, colloquium, talks life little by little, as and when research is stressful. and discussions. In my early possible. It is vital for our Have an occasional days of PhD, I attended almost overall well-being. Spend outing with friends; there all the talks. This helped me half an hour to an hour a day are a lot of good budget- prepare for my talks, and to for personal activities like friendly restaurants in understand what to do and not pursuing a hobby, exercising Bangalore. Ask the locals in a talk. or reading non-academic for lovely places to visit. books. Maintain your health In short, have a life! The non-academic life in IIA as research is stressful. Have was wonderful. I had inspiring an occasional outing with seniors, helpful and supportive friends; there are a lot of good batch-mates, and obliging budget-friendly restaurants in juniors. Even though I was Bangalore. Ask the locals for from Bangalore, I stayed in lovely places to visit. In short, Bhaskara due to the Bangalore have a life! traffic. Life in Bhaskara was pleasant; the common area on each floor was used for occasional recreations and discussions. Annual festivals like New Year, Onam, Christmas and Bengali Durga Sangeetha is a Post Doctoral Artist: Maya Prabhakar pooja feast were celebrated Fellow and her main research PhD student under DST’s Women Scientists fellowship. interest is on magneto-convective with gusto. Such activities flows and waves in the lower solar helped us unwind and relax. atmosphere. * Maya says, “These paintings are inspired works by an amateur artist and the credits go to I hope these fun activities are [email protected] the original artists. As they say, “True artist is not the one who is inspired, but the one who still carried out in current inspires others”. I look up to master this form of art and enrich my creativity.”

56 August 2020 August 2020 57 Location: Bangalore Date: 15th October 2020 October 2020 Time: 20:00 IST October 7 - Draconids Meteor Shower The Draconids is a minor meteor shower producing only about 10 meteors per hour. It is produced by dust grains left behind by comet 21P Giacobini-Zinner, which was first discovered in 1900. The Draconids is an unusual shower in that the best viewing is in the early evening instead of early morning like most other showers. The shower runs annually from October 6-10 and peaks this year on the night of the 7th. The second quarter moon will ensure dark skies in the early evening for what should be a good show. Best viewing will be in the early evening from a dark location far away from city lights. Meteors will radiate from the constellation Draco, but can appear anywhere in the sky.

October 13 - Mars at Opposition The red planet will be at its closest approach to Earth and its face will be fully illuminated by the Sun. It will be brighter than any other time of the year and will be visible all night long. This is the best time to view and photograph Mars. A medium-sized telescope will allow you to see some of the dark details on the planet’s orange surface.

October 21, 22 - Orionids Meteor Shower The Orionids is an average shower producing up to 20 meteors per hour at its peak. It is produced by dust grains left behind by comet Halley, which has been known and observed since ancient times. The shower runs annually from October 2 to November 7. It peaks this year on the night of the 21st and the morning of the 22nd. The waxing crescent moon will set before midnight leaving dark skies for what should be a good show. Best viewing will be from a dark location after midnight. Meteors will radiate from the constellation Orion, but can appear anywhere in the sky. Copyright © 2020 Heavens-Above.com * Everyday stars will rise 4 minutes earlier than previous day October 29, 30 - Southern Taurids Meteor Shower The Southern Taurids is a long-running minor meteor shower producing only about 5-10 meteors per hour. This shower is, however, famous for producing a higher than normal percentage of bright fireballs. The Southern Taurids is produced by debris left behind by Comet Watch out for 2P Encke. The shower runs annually from September 10 to November 20. It peaks this year on the night of the 29th and morning of the 30th. The nearly full moon will block out all but the brightest meteors this year. If you are patient, you may still be able to catch a few good ones. Best viewing will be just after midnight from a dark location far away from city lights. Meteors October 1 - Mercury at Greatest Eastern Elongation will radiate from the constellation Taurus, but can appear anywhere in the sky. The planet Mercury reaches greatest eastern elongation of 25.8 degrees from the Sun. This is the best time to view Mercury since it will be at its highest point above the horizon in the evening sky. Look for the planet low in the western sky just after sunset. October 31 - Uranus at Opposition The blue-green planet will be at its closest approach to Earth and its face will be fully illuminated by the Sun. It will be brighter than any other time of the year and will be visible all night long. This is the best time to view Uranus. Due to its distance, it will only appear as a tiny blue-green dot in all but the most powerful telescopes. DOOT Indian Institute of Astrophysics Review Review Indian Institute of Astrophysics DOOT the prototype, the non-variable stars or HdCs. They have observational limitations? Isn’t hydrogen-deficient carbon stars temperatures of 4000K to 6000K it easier to detect RCBs by (HdCs) and hot extreme helium and share a similar chemical seeing their spectacular light Stars (EHes).’ composition with RCrBs. The curves?’ hotter cousins of the previous R: ‘Variable stars? How do you two groups of stars are known A: ‘Brilliant! In fact, most of understand a star is variable? as Extreme Helium Stars or the RCB stars are discovered A: ‘Astronomers observe the EHes, which are so-called by amateur astronomers brightness of a star at regular due to the presence of high using lightcurves. Brightness intervals. If they find that the amounts of neutral helium variations are much easier to A tale of hydrogen-deficient stars brightness is varying with lines in their spectrum. They monitor than detailed spectrum time in a pattern, it’s called a are hotter (8000K to 30000K), analysis, which is time- Anirban Bhowmick variable star. They plot this non-variable, and helium consuming. That’s why the brightness variation with time, is enhanced with respect to number of detected RCB stars which is called a lightcurve.’ hydrogen by more than 1000 are around 500 in our galaxy times when compared to whereas the two other non- R: ‘Wow! So are there variable normal stars!’ variables HdCs and EHes are ‘Bhaiyya! Do hydrogen- named Ludendorff discovered telescopes with dedicated as well as non-variable stars, R: ‘So there are only three around 5 and 23 only!’ deficient stars really exist?’ the complete absence of surveys, many more were which are hydrogen- asked Rony with amazement. hydrogen in the atmosphere of identified with proper deficient?’ Astronomers observe the brightness of R: ‘So less! Compared ‘Yes! Not only do they exist, another star called R-Coronae classification based on their A: ‘Yes! In fact, one a star at regular intervals. If they find to 200-400 billions of but they also have different Borealis (RCrB). Finally, spectra, mass and temperature. of the most peculiar that the brightness is varying with time stars in our galaxy, the types’ explained Ani. around 1935-1940, after many They are broadly classified into and exciting groups of in a pattern, it’s called a variable star. numbers are basically deliberations, astronomers two based on their mass – the variable stars are the insignificant!’ R: ‘Unbelievable! I always agreed that these two stars are massive hydrogen-deficient RCrB and their counterparts. types of low-mass hdef stars? thought stars shine due to indeed hydrogen-deficient.’ (hdef) stars and low-mass RCrB like stars can suddenly Any chance of finding a new A: ‘Yes, since these stars are nuclear fusion of hydrogen and hydrogen-deficient stars. Some become very faint within a group?’ extremely rare in nature, hence they are hydrogen-rich!’ R: ‘Ok. So are there more stars types of massive hdef-stars are matter of a few days, almost the exact reasons for their A: ‘It’s not just you, even the like these? What is the cause of the Wolf-Rayet stars, hydrogen- disappearing from naked A: ‘Yes, I was about to say that. formation and evolution are astronomers were not ready hydrogen-deficiency? deficient binaries like Upsilon eyesight, slowly recovering Very recently, one more type of merely speculative.’ to accept that stars can be A: ‘Wait! I will answer all of Sgr and hydrogen-deficient after months and sometimes star similar to the above group hydrogen-deficient till 1935.’ your queries. Let me take you supernovae. However, in this years.’ was observed. They are known R: ‘So how do you predict on an exciting journey about story, I will tell you about the as DYPersei variables which their origins? By seeing some R: ‘Oh! How did it change hydrogen-deficient stars and low-mass hdef-stars.’ R: ‘That’s interesting! Tell me may be the coolest member of extraordinary characteristics then?’ my little personal investigation more about them.’ the group (2000K to 4000K) yet common only to them, like A: ‘It all started in 1891 when on them.’ A: ‘The low-mass hdef-stars A: ‘RCrBs are hydrogen- not much is known about them. hydrogen-deficiency?’ a brilliant Scottish woman R: ‘Sure!’ are again divided into three deficient supergiants having They also show an abrupt drop A: ‘Excellent, yes! The only scientist named Williamina principal categories based surface temperatures between in their brightness like RCrBs, way we can connect these stars Fleming found that hydrogen A: ‘Hydrogen-deficient stars on their temperature, surface 5000K to 12000K. Similar to but their rise and drop in and predict their evolution lines are very faint in the are extremely rare and very composition and variability. A RCrBs, there is a cooler group brightness is symmetric.’ is to look at their chemical spectrum of a binary star little was known about them few examples are the peculiar of non-variable hydrogen- composition, the common Upsilon Sgr. A few years even 40 years back. But variables R-Coronae Borealis deficient stars known as R: ‘Wow! You said these peculiarities they share and later in 1906, another scientist with the arrival of modern stars (RCBs), of which RCrB is hydrogen-deficient carbon stars are rare. Is that due to compare with those of normal 60 August 2020 August 2020 61 DOOT Indian Institute of Astrophysics Review Review Indian Institute of Astrophysics DOOT stars.’ Double Degenerate (DD) white are raised to such levels that involve the evolution of stars R: ‘So what about DYPers? Is and EHes, which is an exciting dwarf merger scenario and helium fusion starts again, and near the white dwarf sequence! there any similar connection for result in the research of low- A: ‘In the year 2007, Clayton Final helium shell Flash (FF) the star expands to supergiant So these stars must be super them?’ mass hydrogen-deficient stars. and his team found that the scenario. The DD scenario sizes.’ old!’ cooler ones, the HdCs and supports low 16O/18O, high A: ‘Exactly, that’s why they A: ‘Good question. Most of the R: ‘Wow! Searching for so few cool RCBs (< 6000K) show 12C/ 13C and high fluorine A: ‘Now about the second are so exotic. On top of that, sparsely available literature stars in this gigantic galaxy is considerable enhancement abundances, explaining most case: the stars formed in such a most of the single/binary on DYPersei type stars are like searching for a needle in a of 18O with respect to 16O in of the observed cases, whereas situation are also called Born- white dwarfs may not give on the DYPersei prototype, haystack!’ comparison to normal stars. the FF scenario that doesn’t Again stars. In general, when rise to such enigmatic objects. suggesting it as a cooler RCB A: ‘Yes. But when the While for normal stars predict these anomalies a star is about to become a Based on the probability based on their high 12C/13C needle is finally found, it 16O/18O > 200, for these explains the rest of the white dwarf, hydrogen burns of occurrence of the above ratio. But as a group, the results stitches together all the loose hydrogen deficient stars this observations.’ only in a thin outer layer of scenarios, it is predicted that were mostly unavailable. For threads about the existence ratio is almost unity. They also the star, depositing helium there may be around 2000 hdef the first time, in our paper of enigmatic objects in our found that the 12C/13C ratios R: ‘White dwarf merger! Aren’t below before slowly turning stars in our galaxy.’ Bhowmick et al. 2018, we universe, which may someday for these stars are 5-20 times white dwarfs dead stars? How off. In a few rare cases, the explored the connections of lead to answers about the higher than those of normal does the merger of two faint mass of the deposited helium R: ‘So do you look for similar DYPersei variables with cool origin and existence of all stars. It’s worth mentioning white dwarfs result in such reaches a critical amount signatures in newly discovered RCBs, HdCs and normal the objects in the universe, that a few RCBs showed brightly shining supergiants? known as critical mass, and hydrogen-deficient objects?’ stars based on the observed including us!’ normal values of even with a little A: ‘Yes. We try to determine 16O/18O and 12C/13C ratios 12C/13C and 16O/18O. There are two principal formation scenarios disturbance, violently the abundances of newly determined from the strengths Similarly, Pandey for hydrogen-deficient stars – The Double ignites, ingesting discovered hydrogen-deficient of 12C16O, 13C16O and 12C18O in 2006 found that Degenerate (DD) white dwarf merger all the remaining objects to connect them bands in the 2 microns infrared the warm RCBs (> and the Final helium shell Flash (FF). hydrogen and giving with the observed ones. For region of their spectrum. 8000K) and cool EHes the appearance of example, as I mentioned before We used the instrument show remarkable a helium-burning the cooler stars show enhanced TIRSPEC, mounted on the 2 overabundance in supergiant star. As if 18O. 18O was detected through meter Himalayan Chandra neutral fluorine (F), almost Also, what about the second from the brink of death these molecular lines of 12C18O in the Telescope (HCT) at Indian 800-8000 times higher than case?’ stars are born again like a infrared wavelength region of 2 Astronomical Observatory normal stars.’ phoenix, hence the name Born- microns. As the star gets hotter, IAO, operated by IIA at Hanle, A: ‘In a DD scenario, two Again stars!’ molecular lines disappear. So Ladakh to observe such stars. A: ‘Now, to explain the white dwarfs, mostly a low- we don’t see 18O in hot RCBs Surprisingly, we found most of reasons for these anomalies, mass Helium white dwarf and A: ‘However, the lifetimes or EHes. We instead look for the DYPersei variables are just astronomers tried to simulate a massive CO white dwarf, of born-again stars are very a common anomaly in them, like HdCs and RCBs with very the conditions required to co-evolves in a binary system, short, and they evolve very which in this case was found to low 16O/18O and high 12C/13C create such abundances. and their orbits slowly decay. fast from bright supergiants be overabundance of fluorine. values. This opened up a new Based on these simulations Finally, the massive white to faint white dwarfs. This It suggests that maybe cool venue for research, and with and the observed surface dwarf swallows the low-mass evolution can be observed in HdCs are connected with increasing discoveries of more compositions of hydrogen- one. The ingested helium-rich human timelines (50-60 years), hot EHes through RCBs. DYPersei objects, will help Anirban Bhowmick is a Senior Research Fellow at IIA. He deficient stars, two principal material from the He white which is extraordinary since Proceeding like this, we look us in classifying these stars. works on Hydrogen-deficient formation scenarios stood dwarf forms an envelope they have actual evolutionary for common connections If indeed these DYPersei are star systems. the test of time and rigorous around the massive one. The timelines of millions of years!’ between different groups of cooler cousins of RCBs, then [email protected] observational analyses – The temperature and pressure R: ‘Whoa! Both these scenarios these stars.’ they are related to both HdCs

62 August 2020 August 2020 63 Physics Concepts Indian Institute of Astrophysics DOOT Indian Institute of Astrophysics Experience DOOT

Experience at IIA and a broad research philosophy How to know if you are stuck in the Prashanth Mohan “mirror universe”?

Priya Goyal

Part 1 A question one often asks in helped orient me towards rational thinking. These the context of observations problems in astrophysics. A were also aided by cultural or an experiment is “what graded strategy as espoused exchanges, discussions does it mean?”. The quest by my advisor Prof. Arun on literary works and to find an answer opens up Mangalam served to help contemporary world events multiple paths, some of which address problems and realize and their impact, enabling are more tedious than others. the connecting picture using a balanced world view. My This Covid-19 pandemic be their right. Just like in our It is instructive and highly the most optimal path. This immediate circle of friends, has forced us to live in a universe, you will see an apple rewarding to travel these involved first understanding spouse and research colleagues virtual world, where many falling down from a tree and A mirror universe is paths to learn lessons, search the observations, and methods continue to be a strong source social activities like teaching, stars twinkling in the night sky. just the reflection of our for connections among these of data analysis and then of support in keeping my social conference presentations, Everything looks beautiful and own universe. It has and apply them to future moving on to interpreting the skills and cognitive abilities dance training, karate classes exactly the same as ours. “So everything just like in quests. My research is thus results and placing them in an sharp and alive. (from my personal list), etc. how do you know if you are ours, except that our motivated, by the excitement overall perspective. are happening online. While stuck in the mirror universe?” right will be their left and in interpreting observed participating in one of these, I Well, one way is to perform the our left will be their right. astrophysical phenomena By encompassing a wide scope am sure that at least once we Wu experiment! and trying to understand a for research, IIA provided all would have got confused “big picture” by connecting a much needed avenue for due to the simple fact that The Wu experiment was first sometimes seemingly disparate discussions on areas outside “Left appears right and right performed in 1956 by Chien- diving into the experiment clues. of my immediate work with appears left”, while looking Shiung Wu and her team in let us understand what is so Prashanth is an assistant professor motivated and inspiring at a person or an image on the order to test if weak forces special about it. at the Shanghai Astronomical screen. This is what we call violate Parity symmetry. The My journey as a researcher colleagues and friends. This Observatory, Shanghai, China began by understanding the played an important role in working in the Square Kilometre mirror or reflection asymmetry. results from this experiment Nature loves symmetry. highly interdisciplinary nature shaping and sustaining the Array group. His research Let’s imagine that you are have taken the entire Physics For example, the wings of interests include studies of active of astrophysics that helped sense of excitement. Equally stuck in a mirror universe. community by surprise. Later, galactic nuclei and cataclysmic a butterfly, spider web, a shape the above motivations. important were discussions transients (e.g. gamma-ray A mirror universe is just the Tsung-Dao Lee and Chen-Ning snowflake, a honeycomb, Owing to a background on the philosophy of science, bursts), and extremely high reflection of our own universe. Yang, the theoretical physicists and even a human face are resolution radio interferometric outside of pure science, the our role as researchers, It has everything just like in who proposed this experiment, all symmetrical. Many of the observations of these. ours, except that our right will received the 1957 Nobel Prize bridge courses at IIA and communicating science [email protected] profound ideas in nature the people that taught them through outreach and enabling be their left and our left will in physics for this result. Before manifest themselves as

64 August 2020 August 2020 65 DOOT Indian Institute of Astrophysics Physics Concepts Physics Concepts Indian Institute of Astrophysics DOOT symmetries. There are three Parity symmetry means laws arrow indicates the direction of which makes it distinguishable fundamental symmetries in the of physics are indifferent to the spin angular momentum of from its mirror image. So when physical world (at the particle left- or right-handedness. So, in the Cobalt nuclei. It indicates you perform this experiment level) that are always expected the mirror universe, where the that the spin is clockwise. and observe that the electrons to hold: Charge, Parity, and left is right and vice-versa, the Cobalt 60 is radioactive; it are emitted opposite to the Time. stars would still twinkle. undergoes beta decay via weak direction of spin of the Cobalt nuclear interaction releasing an nucleus, you are in the real

Time symmetry would imply This C, P, and T symmetry electron. universe, while if they are Figure 2: In the real universe electrons are emitted opposite to the direction of nuclear that fundamental interactions ensure that all physical laws emitted in the same direction of spin while in the mirror universe, they are emitted in the same direction of nuclear spin. work in the same way forwards will remain invariant under the spin of the Cobalt nucleus, experiment results will be the or backward in time. That any of these transformations. you are definitely stuck in the same as ours). Does that mean means if there was a tenet So, whether you are in the tenet mirror universe. you are stuck again? No, not universe, the negative universe, They observed that electrons really! or the mirror universe, the were emitted in a preferred Wait, this is not the complete Whether you are in Priya Goyal is a Senior Research physics textbooks will still be direction, which was opposite story. If the mirror universe the tenet universe, the Fellow at IIA and she works on the same as ours. But the Wu to that of the spin angular also happens to be the large scale structures and effects of negative universe, or experiment showed a violation momentum of the nucleus. negative universe (all charges Gravitational lensing on CMBs the mirror universe, [email protected]. of one of these symmetries Now, if we look at the exact are reversed), the symmetry the physics textbooks which we thought are same experiment in the mirror is restored (meaning, the will still be the same fundamental. what will happen? as ours. But the Wu experiment showed a Wu’s Beta Decay Experiment In the mirror world, the violation of one of these Wu and her team cooled direction of the spin of the symmetries which we the Cobalt 60 atoms close to Cobalt nucleus will remain thought are fundamental. Mystic You absolute zero temperature clockwise and hence the and placed them in a strong direction of spin angular Subhamoy Chatterjee universe, where time runs Post-Doctoral Researcher at SwRI, Colorado in the opposite direction to M.Tech-PhD, IIA-CU (2012-2019), ours, the force of gravitational [email protected] attraction between two bodies will still be the same. Sleeping deep in the sea Me, my spirit Charge symmetry on the And mystic you other hand implies that the In absolute harmony interactions remain unaffected With unknowns if we swap the positive and Figure 1: Cobalt 60 atoms placed under the magnetic field B align their spin pointing in the direction of the field. The red arrow indicates the direction of spin Lifting us with mild symphony negative charge. In a negative angular momentum due to the spin in the clockwise direction. Reaching slowly up universe where the electrons Gently illuminated become protons and vice-versa, magnetic field as shown in Fig momentum remains the same. With rays of hope the atoms would still exist and 1. The magnetic field is used But, the direction in which Reaching the contrast we will still breathe air (O2). to align all the Cobalt atoms in electrons are released will be But with a deep memory one preferential direction. The reversed as described in Fig 2, Of mystic you Photo Credit: Anand M N credit: “Day time Moon” by John T Howard 66 August 2020 August 2020 67 DOOT Indian Institute of Astrophysics IIA Stories IIA Stories Indian Institute of Astrophysics DOOT get the comet behind the observatory hence around 9:30 am I moved to another location. We then aligned the tracker to the North Pole and started shooting and it was a good shot as the moon had also gone down.

Exif : Canon 6D with lens 300mm@f/4 Foreground : 1x280sec ISO 6400 with LENR Background : 40x30sec at ISO 3200 Dark : 10x30s with the same settings as the comet shot. Dated: 23/07/2020 Timing between 10:00 pm to Mr. Dorje Angchuk was the first person from 11:30 pm Ladakh to join IAO as a Trainee Engineer during its initial phase. He contributed to the installation and commissioning of the 2 meter HCT, later getting a Tracked on Vixen polarie and stacked in DSS permanent position there. Presently he is Engineer- and blended in photoshop CC in-Charge, IAO.

Photo credit: Dorje Angchuk Neowise COMET over Spituk Monastry. My little boys were interested in seeing the comet and they tagged along only to be disappointed since it was not so clearly visible to naked eyes in a light polluted surroundings.

Once in a life time Capturing the Comet C/2020 F3 (NEOWISE)

Dorje Angchuk

The previous day I had captured the comet from We reached the observatory around 5 pm and my village and it was not so impressive due to after some rest, at around 7.00 pm along with my the light-polluted surrounding, where my two equipment, I started towards the village Khaldo kids also got disappointed. I had to start for and beyond and soon the comet started getting Hanle on 23rd July for the Annual Maintenance visible. It was a great sight to behold when after of the HCT. Till that time I prayed that this comet sometime around 8:30 pm it was visible to the won’t get disintegrated like the Comet SWAN. eyes. I called upon my other colleague for gazing I was getting prepared in my mind for a good and capturing the most photogenic comet in long shot above the observatory since I had the Northern Hemisphere after Hale-Bopp in not rehearsed also for the same. The moon was 1997. It was a once in a lifetime opportunity and already getting brighter and the 23rd night was probably the last chance for us with a comet so supposed to be the closest approach to Earth. So big and visible to naked eyes. The dark sky of I had this very little window of getting a once in Hanle aided for the most beautiful sighting for

a lifetime shot of the comet over IAO. us. Soon I found that it may not be possible to Neo-IAO-Wise COMET VMM(Roman) old Icy Visitor. Photo credit: Dorje Angchuk 68 August 2020 August 2020 69 Journey of Venus (2018-2020) Prabhakaran (Prabhu.S.Kutti)

Venus is the second planet from the Sun image starting from left to right, its apparent and the third brightest object in Earth’s size, and its phase changes over the course of sky after the Sun and Moon. The surface of time. This image is a composite captured over Venus is hidden by an opaque layer of clouds 500 days at an interval of 1-month starting that are formed from sulphuric acid which from the end of 2018 till mid-2020, few months makes it look featureless through telescopic have been missed due to cloudy weather. observation. Venus overtakes Earth every 584 days as it orbits the Sun, it changes from Capture details: the “Evening Star”, visible after sunset, to the Date: December 15, 2018, until June 23, 2020 “Morning Star”, visible before sunrise. As it orbits the Sun, Venus exhibits phases just like Equipment details: 16” newtonian f/4.5 & the Moon. It appears as a small and “full” disc Celestron HD 11” with ZWO 290MC - ES 3x - when it is on the opposite side of the Sun (at IR685nm/ UV-IR cut filter. superior conjunction). Venus shows a larger Daystar quark with Esprit 80ED APO - disc and “quarter phase” at its maximum ZWO1600MM Pro for the Sun. elongations from the Sun, and appears its brightest in the night sky. The planet presents Processing details: a much larger thin “crescent” in telescopic Stacked all the videos in Autostakkert and views as it passes along the near side between sharpened it in Registax then finally created Earth and the Sun. Venus displays its largest the collage with the hydrogen H-Alpha Sun in size and “new phase” when it is between the middle in photoshop Earth and the Sun (at inferior conjunction). Location: Mleiha, UAE Entire phenomena can be observed in this

Mr.Prabhakaran is a well known Amateur Astronomer & Astrophotographer. During the recent Solar eclipse on June 21, 2020 he had taken beautiful images from UAE. When we contacted him for the eclipse image for our magazine title design, he accepted our request without any hesitation. We are thanking him for the eclipse image.

“Journey of Venus” is an internationally recognized project by Mr.Prabhakaran. This was published by NASA in their Instagram. This image was also published in APOD team’s Instagram handle under “Notable images submitted to APOD”.

For more beautiful images, visit his website and follow him on Instagram. Copyrights: Prabhuastrophotography https://www.instagram.com/prabhuskutti/ https://prabhuastrophotography.com/