DOCSLIB.ORG

Copyright by Michael Anthony Gully-Santiago 2015

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Copyright by Michael Anthony Gully-Santiago 2015 Copyright by Michael Anthony Gully-Santiago 2015 The Dissertation Committee for Michael Anthony Gully-Santiago certifies that this is the approved version of the following dissertation: Innovative Technologies for and Observational Studies of Star and Planet Formation Committee: Daniel Jaffe, Supervisor John Lacy Neal Evans Adam Kraus Alycia Weinberger Innovative Technologies for and Observational Studies of Star and Planet Formation by Michael Anthony Gully-Santiago, B.A. ASTRO. & PHYS. DISSERTATION Presented to the Faculty of the Graduate School of The University of Texas at Austin in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY THE UNIVERSITY OF TEXAS AT AUSTIN May 2015 Dedicated to all my teachers. Acknowledgments This work would not have been possible without the mentorship of my collaborators Katelyn Allers and Alycia Weinberger, for which I am deeply indebted. I acknowledge the mentorship and patience of my former student colleagues Dr. Jasmina Marsh and Dr. Casey Deen. I am grateful for the efforts of my junior colleagues Jared Rand, Amanda Turbyfill, and Carleen Boyer for their contributions to the Silicon Diffractive Optics Group. Engineers Weisong Wang and Cindy Brooks contributed substantially to the Si diffractive optics fabrication. I am indebted to my NASA GRSP mentor Daniel Wilson, with whom it was a pleasure to work. I am thankful for the supervision of Richard Muller and Victor White at the Microdevices Laboratory. Sungho Lee, Hyeonju Jeong, Taylor Chonis, Mike Pavel, Michelle Grigas, Neal Evans, John Lacy, and Adam Kraus, Rachel Walker, and Gordon Orris made this work possible. I am delighted to acknowledge support from the NASA Graduate Stu- dent Research Program (GSRP) Fellowship, grant NNX10AK82H. Portions of this research were supported by NASA APRA grant NNX10AC68G, NASA ACT grant NNX12AC31G, NSF ATI grant AST-0705064, and NASA Origins grant number NNX07AI83G. MGS acknowledges support from the Univer- sity of Texas in the form of the Graduate Dean's Prestigious Fellowship and v from the Department of Astronomy in the form of the David Benfield Memo- rial Fellowship in Astronomy. Funding from the McDonald Observatory and the Department of Astronomy's Cox graduate student excellence funds have helped to support travel and other aspects of this research. Part of the re- search was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Ad- ministration. Some of the work was carried out at the University of Texas under a contract from the University of Arizona. The development work for the grisms was supported in part by NASA (grant number NNX07AV15H). The authors wish to thank Gary Poczulp and the National Optical Astronomy Observatory for assistance in producing some interferograms of early grating prototypes. Thank you to David Hogg, Dan Foreman-Mackey, Jonathan Sick, Jake Vanderplas, and the participants and organizers of the Astro Data Hack Week (2014). This dissertation includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile. I was lucky to be part of such a talented and creative group of incoming graduate students- Chris, John, Chalence, JJ, Julie, Manuel, Erik, Paul, and Manos. I look forward to following their promising careers, and crossing paths indefinitely. Joi Ito and Datri Bean enhanced my creativity. Thank you to my supportive family members Diana, Tony, Erika, and Vanessa who gave me mettle. Thank you to Carol for bringing Chelsey into the world, to Alese for introducing us, and to Chelsey for being exceptionally supportive. Thanks to Mr. Emerson who got me started in astronomy. Thanks to all my friends. vi I acknowledge the kindness of the Wolchover family, who have always been outstanding in their field. A very special thank you is reserved for my advisor, Daniel Jaffe, for contributing so deeply to my professional growth. In particular I acknowledge his patient editing of the prose in this document. vii Innovative Technologies for and Observational Studies of Star and Planet Formation Publication No. Michael Anthony Gully-Santiago, Ph.D. The University of Texas at Austin, 2015 Supervisor: Daniel Jaffe I summarize the optical design, fabrication, and performance of sili- con diffractive optics for astronomical spectrographs. The first set of optical devices includes diffraction-limited, high-throughput silicon grisms for JWST- NIRCam. These grisms served as pathfinders to Silicon immersion gratings, which offer size and cost savings for high-resolution near-infrared spectro- graphs. I demonstrate the production and optical evaluation of the immersion grating that enabled IGRINS at the McDonald Observatory. This grating pro- vides spectral resolution R = 40; 000 over the H− and K− near-infrared band atmospheric windows (1.5−2.5 µm). Electron-beam lithography offers much higher precision over contact mask photolithography for the production of Si immersion gratings. Electron-beam patterned prototypes are stepping-stones to monolithic Si gratings for iSHELL and GMTNIRS. The monolithic design viii of Si immersion gratings presents a limitation for scaling up the grating size, since existing fabrication equipment cannot handle monolithic silicon pucks. The size limitation can be overcome by direct-bonding Si substrates to op- tical prisms. I demonstrate a technique to measure interfacial gaps as small as 14 nm between the bonding interfaces, which produce 0.2% transmission loss. These technologies will enable the direct measurement of the atmospheric properties of extrasolar planets in the next decade. IGRINS is now measuring fundamental properties of young T-Tauri stars; low mass young brown dwarfs are below the sensitivity limit of existing high spectral resolution near-IR spec- trographs. My approach to the discovery and characterization of young brown dwarfs therefore employs low resolution (R ∼ 2000) near-IR spectroscopy. I confirm and characterize 17 candidate young stars and brown dwarfs reported by Allers and collaborators. All 17 sources have circumstellar disks. Using deep optical, near-infrared, and mid-infrared photometry, I search an off-core region towards the nearby ∼ 1 Myr Ophiuchus star forming clus- ter for candidate young stars and brown dwarfs. Multi-object I−band spec- troscopy of 419 candidates reveals 12 new members. Ten of these have no evidence for mid-IR excess emission from 3.6 to 8.0 µm. The disk fraction for spectral types M4 and later towards this region of Ophiuchus is 5/15. Two of the disk sources have edge-on disks, pointing to a high edge-on disk fraction. I discuss possible sources of contamination in the survey. ix Table of Contents Acknowledgments v Abstract viii List of Tables xv List of Figures xvii Chapter 1. Introduction 1 1.1 Innovative Technologies for Star and Planet Formation . .1 1.2 Observational Studies of Star and Planet Formation . .8 1.3 Summary . 15 Chapter 2. High Performance Silicon Grisms for 1.2-8.0 µm: Detailed Results from the JWST-NIRCam Devices 16 2.1 Introduction . 16 2.2 Discussion of Loss Mechanisms . 18 2.2.1 Surface Flatness . 18 2.2.2 Groove Geometry . 20 2.2.3 Microscopic Surface Roughness . 21 2.2.4 Fresnel Losses . 21 2.3 Results of Anti-Reflection Coating . 22 2.4 Conclusions . 28 Chapter 3. Near infrared metrology of high performance silicon immersion gratings 30 3.1 Introduction . 30 3.2 Overview . 31 3.3 Efficiency . 34 x 3.4 Refractive index dependence . 38 3.5 Periodic errors, ghosts, and large scale performance . 41 3.6 Measurement setup description . 44 Chapter 4. High Performance Si Immersion Gratings Patterned with Electron Beam Lithography 46 4.1 INTRODUCTION . 46 4.2 On-sky performance of Si immersion grating . 48 4.3 Motivations for direct writing Si immersion gratings . 49 4.3.1 Motivation #1: Higher precision than contact lithog- raphy . 50 4.3.2 Motivation #2: Finer groove pitch capability . 51 4.4 e-beam patterning strategies . 51 4.4.1 e-beam patterning scale size hierarchy . 52 4.4.1.1 e-beam step size and spot size . 54 4.4.1.2 Subfield deflector . 55 4.4.1.3 Field deflector . 56 4.4.1.4 Interplay of hierarchy at boundaries and de- sign rules . 56 4.4.2 Predicting the ghost level associated with field posi- tioning errors . 59 4.4.3 Employ multiple field sizes rather than one field size 61 4.4.4 Strategies for mitigating facet position errors attributable to large scale stage drift . 63 4.4.5 Characterization of e-beam stage drift . 63 4.5 Results: Test gratings produced with e-beam patterning . 65 4.5.1 Measurement of ghost levels for a variety of writing strategies . 65 4.5.2 Improvement in wavefront performance from drift cor- rection . 67 4.6 Limitations of direct writing Si immersion gratings . 67 4.6.1 Serial write process yields long write times . 67 4.6.2 Large per-part investment cost yields heightened pro- cess risk . 70 4.6.3 Experiments with negative resist . 70 4.7 Conclusions . 71 xi Chapter 5. Optical characterization of gaps in directly bonded Si compound optics using infrared spectroscopy 73 5.1 Introduction . 73 5.2 Si−Si Fabry P`erotmeasurement theory . 78 5.2.1 The Si−Si interface gap is a low finesse Fabry-P`erot etalon . 78 5.2.2 Predicted transmission spectrum for bonded Si with finite interface gap . 82 5.3 Laboratory demonstration: Embedding gaps of known sizes . 85 5.3.1 IR bubble imaging and limitations . 89 5.4 Measurement technique and correlated measurement errors . 90 5.5 Results of infrared spectroscopy of directly bonded Si . 92 5.5.1 Spectra of direct bonded Si with known gap sizes . 95 5.5.2 Spatially resolved measurements with Sample Trans- port Accessory . 96 5.5.3 What is the smallest gap this technique can detect? .
Load more

Recommended publications
  • Observer's Handbook 1974
    the OBSERVER’S HANDBOOK 1974 sixty- sixth year of publication the ROYAL ASTRONOMICAL SOCIETY of CANADA THE ROYAL ASTRONOMICAL SOCIETY OF CANADA Incorporated 1890 Federally Incorporated 1968 The National Office of the Society is located at 252 College Street, Toronto 130, Ontario; the business office, reading room and astronomical library are housed here. Membership is open to anyone interested in astronomy and applicants may affiliate with one of the eighteen Centres across Canada established in St. John’s, Halifax, Quebec, Montreal, Ottawa, Kingston, Hamilton, Niagara Falls, London, Windsor, Winnipeg, Saskatoon, Edmonton, Calgary, Vancouver, Victoria and Toronto, or join the National Society direct. Publications of the Society are free to members, and include the Jo u r n a l (6 issues per year) and the O bserver’s H a n d b o o k (published annually in November). Annual fees of $12.50 ($7.50 for full-time students) are payable October 1 and include the publications for the following calendar year. VISITING HOURS AT SOME CANADIAN OBSERVATORIES Burke-Gaffney Observatory, Saint Mary’s University, Halifax, Nova Scotia. October-April: Saturday evenings 7:00 p.m. May-September: Saturday evenings 9:00 p.m. David Dunlap Observatory, Richmond Hill, Ontario. Wednesday mornings throughout the year, 10:00 a.m. Saturday evenings, April through October (by reservations, tel. 884-2112). Dominion Astrophysical Observatory, Victoria, B.C. May-August: Daily, 9:15 a.m.-4:30 p.m. (Guide, Monday to Friday). Sept.-April: Monday to Friday, 9:15 a.m.-4:30 p.m. Public observing, Saturday evenings, April-October, inclusive.
    [Show full text]
  • FY13 High-Level Deliverables
    National Optical Astronomy Observatory Fiscal Year Annual Report for FY 2013 (1 October 2012 – 30 September 2013) Submitted to the National Science Foundation Pursuant to Cooperative Support Agreement No. AST-0950945 13 December 2013 Revised 18 September 2014 Contents NOAO MISSION PROFILE .................................................................................................... 1 1 EXECUTIVE SUMMARY ................................................................................................ 2 2 NOAO ACCOMPLISHMENTS ....................................................................................... 4 2.1 Achievements ..................................................................................................... 4 2.2 Status of Vision and Goals ................................................................................. 5 2.2.1 Status of FY13 High-Level Deliverables ............................................ 5 2.2.2 FY13 Planned vs. Actual Spending and Revenues .............................. 8 2.3 Challenges and Their Impacts ............................................................................ 9 3 SCIENTIFIC ACTIVITIES AND FINDINGS .............................................................. 11 3.1 Cerro Tololo Inter-American Observatory ....................................................... 11 3.2 Kitt Peak National Observatory ....................................................................... 14 3.3 Gemini Observatory ........................................................................................
    [Show full text]
  • Abstracts of Extreme Solar Systems 4 (Reykjavik, Iceland)
    Abstracts of Extreme Solar Systems 4 (Reykjavik, Iceland) American Astronomical Society August, 2019 100 — New Discoveries scope (JWST), as well as other large ground-based and space-based telescopes coming online in the next 100.01 — Review of TESS’s First Year Survey and two decades. Future Plans The status of the TESS mission as it completes its first year of survey operations in July 2019 will bere- George Ricker1 viewed. The opportunities enabled by TESS’s unique 1 Kavli Institute, MIT (Cambridge, Massachusetts, United States) lunar-resonant orbit for an extended mission lasting more than a decade will also be presented. Successfully launched in April 2018, NASA’s Tran- siting Exoplanet Survey Satellite (TESS) is well on its way to discovering thousands of exoplanets in orbit 100.02 — The Gemini Planet Imager Exoplanet Sur- around the brightest stars in the sky. During its ini- vey: Giant Planet and Brown Dwarf Demographics tial two-year survey mission, TESS will monitor more from 10-100 AU than 200,000 bright stars in the solar neighborhood at Eric Nielsen1; Robert De Rosa1; Bruce Macintosh1; a two minute cadence for drops in brightness caused Jason Wang2; Jean-Baptiste Ruffio1; Eugene Chiang3; by planetary transits. This first-ever spaceborne all- Mark Marley4; Didier Saumon5; Dmitry Savransky6; sky transit survey is identifying planets ranging in Daniel Fabrycky7; Quinn Konopacky8; Jennifer size from Earth-sized to gas giants, orbiting a wide Patience9; Vanessa Bailey10 variety of host stars, from cool M dwarfs to hot O/B 1 KIPAC, Stanford University (Stanford, California, United States) giants. 2 Jet Propulsion Laboratory, California Institute of Technology TESS stars are typically 30–100 times brighter than (Pasadena, California, United States) those surveyed by the Kepler satellite; thus, TESS 3 Astronomy, California Institute of Technology (Pasadena, Califor- planets are proving far easier to characterize with nia, United States) follow-up observations than those from prior mis- 4 Astronomy, U.C.
    [Show full text]
  • Theia: Faint Objects in Motion Or the New Astrometry Frontier
    Theia: Faint objects in motion or the new astrometry frontier The Theia Collaboration ∗ July 6, 2017 Abstract In the context of the ESA M5 (medium mission) call we proposed a new satellite mission, Theia, based on rel- ative astrometry and extreme precision to study the motion of very faint objects in the Universe. Theia is primarily designed to study the local dark matter properties, the existence of Earth-like exoplanets in our nearest star systems and the physics of compact objects. Furthermore, about 15 % of the mission time was dedicated to an open obser- vatory for the wider community to propose complementary science cases. With its unique metrology system and “point and stare” strategy, Theia’s precision would have reached the sub micro-arcsecond level. This is about 1000 times better than ESA/Gaia’s accuracy for the brightest objects and represents a factor 10-30 improvement for the faintest stars (depending on the exact observational program). In the version submitted to ESA, we proposed an optical (350-1000nm) on-axis TMA telescope. Due to ESA Technology readiness level, the camera’s focal plane would have been made of CCD detectors but we anticipated an upgrade with CMOS detectors. Photometric mea- surements would have been performed during slew time and stabilisation phases needed for reaching the required astrometric precision. Authors Management team: Céline Boehm (PI, Durham University - Ogden Centre, UK), Alberto Krone-Martins (co-PI, Universidade de Lisboa - CENTRA/SIM, Portugal) and, in alphabetical order, António Amorim
    [Show full text]
  • Physics of Stellar Coronae
    Physics of Stellar Coronae Manuel G¨udel Paul Scherrer Institut, W¨urenlingen and Villigen, CH-5232 Villigen PSI, Switzerland [email protected] 1 Introduction For the plasma physicist, the solar corona offers an outstanding example of a space plasma, and surely one that deserves a lifetime of study. Not only can we observe the solar corona on scales of a few hundred kilometers and monitor its changes in the course of seconds to minutes, we also have a wide range of detailed diagnostics at our disposal that provide immediate access to the prevalent physical processes. Yet, solar physics offers a rich field of unsolved plasma-physical problems. How is the coronal plasma continuously heated to > 106 K? How and where are high-energy particles episodically accelerated? What is the internal dy- namics of plasma in magnetic loops? What is the initial trigger of a coronal flare? How does the corona link to the solar wind, and how and where is the latter accelerated? How is plasma transported into the solar corona? Why, then, study stellar coronae that remain spatially unresolved in X- rays and are only marginally resolved at radio wavelengths, objects that require exposure times of several hours before approximate measurements of the ensemble of plasma structures can be obtained? There are many reasons. In the context of the solar-stellar connection, stellar X-ray astronomy has introduced a range of stellar rotation periods, gravities, masses, and ages into the debate on the magnetic dynamo. Coronal magnetic structures and heating mechanisms may vary together with varia- tions of these parameters.
    [Show full text]
  • Faint Objects in Motion: the New Frontier of High Precision Astrometry
    White paper for the Voyage 2050 long-term plan in the ESA Science Programme Faint objects in motion: the new frontier of high precision astrometry Contact Scientist: Fabien Malbet Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) Université Grenoble Alpes, CS 40700, F-38058 Grenoble cedex 9, France Email: [email protected], Phone: +33 476 63 58 33 version 20190805 Faint objects in motion : the new frontier of high precision astrometry Faint objects in motion: the new on the most critical questions of cosmology, astron- frontier of high precision astrometry omy and particle physics. Sky survey telescopes and powerful targeted telesco- 1.1 Dark matter pes play complementary roles in astronomy. In order to The current hypothesis of cold dark matter (CDM) ur- investigate the nature and characteristics of the mo- gently needs verification. Dark matter (DM) is essential tions of very faint objects, a flexibly-pointed instrument to the L + CDM cosmological model (LCDM), which suc- capable of high astrometric accuracy is an ideal comple- cessfully describes the large-scale distribution of galax- ment to current astrometric surveys and a unique tool for ies and the angular fluctuations of the Cosmic Microwave precision astrophysics. Such a space-based mission Background, as confirmed by the ESA / Planck mission. will push the frontier of precision astrometry from ev- Dark matter is the dominant form of matter (∼ 85%) in idence of earth-massed habitable worlds around the the Universe, and ensures the formation and stability of nearest starts, and also into distant Milky way objects enmeshed galaxies and clusters of galaxies.
    [Show full text]
  • Sky Notes: 2013 August & September
    Sky Notes: 2013 August & September by Brian Mills − (Written for 22:00 UT on 2013 September 1.) the other members of the Summer Triangle evening position of the ecliptic is the cause of Altair in Aquila, which is always easy to iden- our problems from the UK at this time of year, In the north Ursa Major has almost completed tify because of the two stars (β and γ Aquilae) being at most 15° high. This means that it makes its descent towards the horizon meaning that on that attend it on either side. a very shallow angle with the horizon, not helped the opposite side of the pole, Cassiopeia is climb- Lower, but still on the meridian, is Capricornus by the fact that Mercury is almost 3° below the ing and Cepheus is approaching culmination not which contains the globular cluster M30, visible ecliptic when the next elongation occurs in the far from the zenith. There are a number of open in larger binoculars although a moder- clusters that fall within the borders of Cepheus, ate sized telescope is needed to begin the brightest being NGC 7160 which lies inside resolving individual stars. Lower still the quadrilateral that makes up the main body of lies the small and insignificant the constellation. At magnitude 6.1 it requires Microscopium. On a really clear only a small telescope or binoculars. Cassiopeia evening it is worth trying to locate its also has its share of such clusters, the best known brightest stars; gamma (γ) at magnitude of which are M52 (magnitude 6.9) and NGC457 4.67 and epsilon (ε) at 4.71 despite their (magnitude 6.4).
    [Show full text]
  • Gaia FGK Benchmark Stars: Effective Temperatures and Surface Gravities U
    Astronomy & Astrophysics manuscript no. Heiter_etal_Benchmarkstars_LE c ESO 2018 September 25, 2018 Gaia FGK benchmark stars: Effective temperatures and surface gravities U. Heiter1, P. Jofré2, B. Gustafsson1; 4, A. J. Korn1, C. Soubiran3, and F. Thévenin5 1 Institutionen för fysik och astronomi, Uppsala universitet, Box 516, 751 20 Uppsala, Sweden e-mail: [email protected] 2 Institute of Astronomy, University of Cambridge, Madingley Rd, Cambridge, CB3 0HA, U.K. 3 Univ. Bordeaux, CNRS, LAB, UMR 5804, 33270, Floirac, France 4 Nordita, Roslagstullsbacken 23, 106 91, Stockholm, Sweden 5 Université de Nice Sophia Antipolis, CNRS (UMR7293), Observatoire de la Côte d’Azur, CS 34229, 06304, Nice Cedex 4, France Received / Accepted ABSTRACT Context. In the era of large Galactic stellar surveys, carefully calibrating and validating the data sets has become an important and integral part of the data analysis. Moreover, new generations of stellar atmosphere models and spectral line formation computations need to be subjected to benchmark tests to assess any progress in predicting stellar properties. Aims. We focus on cool stars and aim at establishing a sample of 34 Gaia FGK benchmark stars with a range of different metallicities. The goal was to determine the effective temperature and the surface gravity independently of spectroscopy and atmospheric models as far as possible. Most of the selected stars have been subjected to frequent spectroscopic investigations in the past, and almost all of them have previously been used as reference, calibration, or test objects. Methods. Fundamental determinations of Teff and log g were obtained in a systematic way from a compilation of angular diameter measurements and bolometric fluxes and from a homogeneous mass determination based on stellar evolution models.
    [Show full text]
  • Extrasolar Planets and Their Host Stars
    Kaspar von Braun & Tabetha S. Boyajian Extrasolar Planets and Their Host Stars July 25, 2017 arXiv:1707.07405v1 [astro-ph.EP] 24 Jul 2017 Springer Preface In astronomy or indeed any collaborative environment, it pays to figure out with whom one can work well. From existing projects or simply conversations, research ideas appear, are developed, take shape, sometimes take a detour into some un- expected directions, often need to be refocused, are sometimes divided up and/or distributed among collaborators, and are (hopefully) published. After a number of these cycles repeat, something bigger may be born, all of which one then tries to simultaneously fit into one’s head for what feels like a challenging amount of time. That was certainly the case a long time ago when writing a PhD dissertation. Since then, there have been postdoctoral fellowships and appointments, permanent and adjunct positions, and former, current, and future collaborators. And yet, con- versations spawn research ideas, which take many different turns and may divide up into a multitude of approaches or related or perhaps unrelated subjects. Again, one had better figure out with whom one likes to work. And again, in the process of writing this Brief, one needs create something bigger by focusing the relevant pieces of work into one (hopefully) coherent manuscript. It is an honor, a privi- lege, an amazing experience, and simply a lot of fun to be and have been working with all the people who have had an influence on our work and thereby on this book. To quote the late and great Jim Croce: ”If you dig it, do it.
    [Show full text]
  • The Observer of the Twin City Amateur Astronomers
    THE OBSERVER OF THE TWIN CITY AMATEUR ASTRONOMERS Volume 43, Number 12 December 2018 INSIDE THIS ISSUE: 1«Editor’s Choice: December Image – Full Moon 1«3rd Mag Comet 46P/Wirtanen on its Way 2«President’s Note 3«Calendar of Celestial Events – December 2018 3«New & Renewing Members/Dues Blues/E-Mail List 4«This Month’s Phases of the Moon 4«This Month’s Solar Phenomena 4«AstroBits – News from Around the TCAA 5«The Pleiades and a Minor Planet 6«TCAA Saturnalia Party December 7th 6«Basic Small Scope Lunar Imaging 11«December 2018: Morning Planet Dance 16«Minutes of the November 27th Board Meeting 17«ISU Planetarium Renovations Noted 18«ISU Planetarium Holiday Offering 18«Call for Nominations 18«Dave Osenga’s Father Passes Away 18«Education/Public Outreach for November 2018 19«Public Viewing Schedule for 2019 19«TCAA Calendar of Events for 2018-2019 20«HowTimeFlies 20«Renewing Your TCAA Membership EDITOR’S CHOICE: IMAGE OF THE MONTH – FULL MOON 21«TCAA Treasurer’s Report as of November 30, 2018 This month’s Editor’s Choice is a picture of the Thanksgiving full moon by Tim Stone. 3RD MAG COMET 46P/WIRTANEN ON ITS WAY http://bit.ly/2BHqLTW The TCAA is an affiliate of the Astronomical League. For more information about the TCAA, be certain to visit the TCAA website. Visit Astroleague.org for additional information about the League and its membership benefits. Copyright © 2018 TCAA 1 All rights reserved. Vol. 43, No. 12 The OBSERVER of the Twin City Amateur Astronomers December 2018 PRESIDENT’S NOTE The OBSERVER With the Holiday season in full swing, it’s is the monthly electronic newsletter of Twin time for family and friends to enjoy each other City Amateur Astronomers, Inc., a registered 501(c)(3) non-profit educational and reflect upon a successful year.
    [Show full text]
  • Wadhurst Astronomical Society Newsletter September 2013
    Wadhurst Astronomical Society Newsletter September 2013 MEETINGS SOCIETY ASTRO-BARBECUE During August there is no meeting of the Society but we usually have a barbecue with telescopes present to look at what is in the night sky. It was with sadness that, for the first time the Astro-barbeque had to be cancelled this year through appalling weather. We waited as late as possible to make the decision, but it became obvious that the rain wasn’t going to clear up. We would like to thank Jim Cooper for arranging for the barbeque to be held in his garden and also to those who were helping to make it the success it has been in the past and must feel very disappointed. We must be owed to really good evening some time so we look forward to next year. SEPTEMBER MEETING Wednesday 18th September 2013 – Stephen Tonkin will be talking about “Binocular Astronomy”. Stephen is a freelance writer and lecturer in astronomy. He has had articles published in the Sky at Night magazine and is a keen amateur astronomer. Later this year we are hoping to be amazed by the appearance of comet ISON in November and comets are one of the most enjoyable sights using just a pair of binoculars; even a modest pair. So this talk should be a good preparation for this event. FUTURE MEETINGS Wednesday 16th October 2013 – James Fradgely FRAS calls his talk “The Birth of the Solar System” Wednesday 20th November 2013 – Tony Roberts FRAS tells us about “The History of the Telescope up to 1960” Wednesday 11th December 2013 – (the second Wednesday of this month only) Our Director of Observations, Brian Mills FRAS takes as his theme “The Star of Bethlehem”.
    [Show full text]
  • The Sun in Time: Activity and Environment
    The Sun in Time: Activity and Environment Manuel G¨udel Paul Scherrer Institute, W¨urenlingen and Villigen, CH-5232 Villigen PSI, Switzerland and Max-Planck-Institute for Astronomy, K¨onigstuhl 17, D-69117 Heidelberg, Germany email: [email protected] http://www.astro.phys.ethz.ch/staff/guedel/guedel.html Abstract The Sun’s magnetic activity has steadily declined during its main-sequence life. While the solar photospheric luminosity was about 30% lower 4.6 Gyr ago when the Sun arrived on the main sequence compared to present-day levels, its faster rotation generated enhanced magnetic activity; magnetic heating processes in the chromosphere, the transition region, and the corona induced ultraviolet, extreme-ultraviolet, and X-ray emission about 10, 100, and 1000 times, respectively, the present-day levels, as inferred from young solar-analog stars. Also, the production rate of accelerated, high-energy particles was orders of magnitude higher than in present-day solar flares, and a much stronger wind escaped from the Sun, permeating the entire solar system. The consequences of the enhanced radiation and particle fluxes from the young Sun were potentially severe for the evolution of solar-system planets and moons. Interactions of high-energy radiation and the solar wind with upper planetary atmospheres may have led to the escape of important amounts of atmospheric constituents. The present dry atmosphere of Venus and the thin atmosphere of Mars may be a product of early irradiation and heating by solar high-energy radiation. High levels of magnetic activity are also inferred for the pre-main sequence Sun.
    [Show full text]