The Arecibo Observatory The Arecibo Observatory Newsletter

May-June 2016

Highlights

Galaxy

Neutral Structures Trace Polarization Angle: Implications for Cosmic Microwave Background Foregrounds

Welcome to our AO Newsletter, our AO Newsletter celebrates the new, fundamental, cutting-edge done at the Arecibo Observatory. A relaunch of the newsletter has been a recommendation of our Users Committee, but it was hard to do Physical Characterization of ~2-meter with a scientific staff that has been described as a “skeleton crew.” As I was struggling Diameter Near- 2015 TC25: A possible boulder from E-type Asteroid (44) to find a way to implement this recommendation, I was inspired Nysa by a summary of scientific work written by one of Arecibo’s own users –it put the discovery in context, it described Arecibo’s essential contributions, it used a minimum Atmosphere amount of sub-discipline specific jargon, and it had a First Simultaneous Measurements of Na and cool picture! In short, it would make the perfect K Thermospheric Layers along with TILs newsletter article. I realized that we could indeed from Arecibo produce an AO Newsletter, but only if we asked our users for a bit of help. After all, no one knows your results better than you do! Please enjoy reading about the remarkable science done at the Arecibo Fast Radio Burst

Observatory. I hope the discoveries inspire you as In the last decade, radio telescopes have much as they inspire me. started to detect mysterious signals called “Fast Radio Bursts” (FRBs). The FRBs are radio flashes that last for only a few - Joan Schmelz, milliseconds Arecibo Observatory and USRA Neutral Hydrogen Structures Trace Dust Polarization Angle: Implications for Cosmic Microwave Background Foregrounds Authors: Susan E. Clark, J. Colin Hill, Joshua E.G. Peek, Mary E. Putman, Brian L. Babler

Abstract: In the first trillionth of a trillionth of a billionth of a second after diffuse material between the in the . The interstellar the , the is thought to have experienced a medium is also full of gas, much of which is neutral hydrogen. Here, growth spurt – a period of rapid expansion known as inflation. we present the discovery that slender linear filaments of neutral Cosmological observations provide strong circumstantial hydrogen gas in the Milky Way, revealed by high-resolution Arecibo evidence for inflation, but no direct detection thus far. The survey data, are extremely well aligned with the dust polarization. predicted "smoking gun" evidence for inflation is primordial This means that structures in the gas are strongly aligned with the B-mode polarization. These “B-modes” are a polarization ambient magnetic field. We use a machine vision algorithm to pattern imprinted in the cosmic microwave background (CMB), measure the orientation of the Arecibo filaments. The shape of Edgard Rivera-Valentín, a native of neutral hydrogen provides an entirely new way to constrain the dust Arecibo Puerto Rico, is a staff planetary the pervasive leftover radiation from the Universe’s formation. scientist at the Arecibo Observatory. In Unfortunately, despite enormous experimental effort, the polarization foreground obscuring the inflationary B-mode signal. 2008, he earned a bachelor's degree in Our work will allow astrophysicists to more precisely measure the Physics and Mathematics at Alfred B-mode signal has yet to be detected because it is obscured by University, where he also minored in polarized dust in our . Galactic dust grains emit polarized foreground dust signal, improving our ability to uncover the planetary science, a program he pioneered signature of inflation. and helped build at Alfred. In the summer light because they are aligned with the interstellar magnetic of 2007, he had the to field, creating a signal that must be carefully measured and participate in the Lunar and Planetary subtracted from CMB data in order to uncover the inflationary This work would not have been possible without Arecibo. The Institute’s REU program, where he worked with Drs. Michelle Kirchoff and Paul Schenk B-mode signal. sensitive, high dynamic range Galactic Arecibo L-Band Feed Array on impact cratering of ’s icy . (GALFA) HI Survey revealed the slender, magnetically aligned neutral He went on to the University of Arkansas hydrogen structures. for his graduate studies where in 2012 he This dust is a component of the interstellar medium – all the earned a Ph.D. in Space and Planetary Sciences. His thesis topic concerned surface-atmosphere interactions and volatile transfer. Ed did his postdoctoral work at Brown University in the Department of Earth, Environmental, and Planetary Sciences under advisement of Dr. Amy Barr studying impact-induced processes on solid bodies.

His current research focuses on two major areas, Formation and Evolution, and Astrobiology. Ed uses observations paired with simulations to unravel the processes that led to the formation of the icy moons of Jupiter and as well as processes that drove the evolution of the interior rocky worlds. Additionally, he studies aqueous processes on in search for habitable abodes beyond Earth. He teaches every summer at the Alfred University Astronomy Institute for High School Students and at AO he is the Project Manager for the Arecibo Observatory Space Academy.

The top frame is a visualization of the orientation of linear HI structures across a swath of high-latitude sky. The lower frame shows the orientation of the magnetic field as measured by the Planck satellite's observations of polarized dust emission. The overlaid white pseudo-vectors show the orientation of polarized starlight. Physical Characterization of ~2-meter Diameter Near-Earth Asteroid 2015 TC25: A possible boulder from E-type Asteroid (44) Nysa Authors: Vishnu Reddy, Juan A. Sanchez, William F. Bottke, Audrey Thirouin, Edgard G. Rivera-Valentin, Patrick A. Taylor, Michael S. Kelley, William Ryan, Edward A. Cloutis, Stephen C. Tegler, Eileen V. Ryan, Nicholas Moskovitz Submitted to the Astrophysical Journal. Know Abstract: Small bodies in the solar system are time very fast rotator with a period of 133 seconds. We capsules that have recorded the conditions compared spectral and dynamical properties of our during formation. Studying these 2015 TC25 and found the best candidate source objects will not only help us better body in the inner main belt to be the 70-km understand how our planet formed, but also diameter E-type asteroid (44) Nysa. Using the staff how large impacts help shape the course of of E-type asteroids (50-60%), we refine the on Earth. The Chelyabinsk bolide that diameter of 2015 TC25 to 2-meters making it one Edgard Rivera-Valentín, a native of entered Earth's atmosphere over Russia in of the smallest NEAs ever to be characterized and Arecibo Puerto Rico, is a staff planetary 2013 reminds us of the threats posed by small the smallest NEA ever detected by the Arecibo scientist at the Arecibo Observatory. In 2008, he earned a bachelor's degree in near-Earth asteroids (NEAs) with diameters radar. Physics and Mathematics at Alfred <20 meters. Furthermore, small NEAs are the University, where he also minored in progenitors for in our terrestrial The Arecibo Observatory planetary radar system, planetary science, a program he pioneered and helped build at Alfred. In the summer collection. The physical characteristics of which is funded through NASA’s Near-Earth of 2007, he had the opportunity to these small NEAs are crucial to our Object Observation Program, provides crucial participate in the Lunar and Planetary Institute’s REU program, where he worked understanding of the effectiveness of our information for the assessment of impact with Drs. Michelle Kirchoff and Paul Schenk atmosphere in filtering these low-strength hazards from near-Earth objects, as well as on impact cratering of Jupiter’s icy moons. He went on to the University of Arkansas impactors, but characterization has been a invaluable information on the object’s size, for his graduate studies where in 2012 he challenge because of the difficulty in shape, mass, spin, and constraints on the earned a Ph.D. in Space and Planetary Sciences. His thesis topic concerned detecting them prior to close Earth flyby. composition. Such characterization further surface-atmosphere interactions and refines the orbit determination, extending volatile transfer. Ed did his postdoctoral NEA 2015 TC25 was first observed on October predictions by 80 to 400 years compared to work at Brown University in the Department of Earth, Environmental, and 11, 2015 and a quick response campaign was single-apparition optical measurements. Indeed, Planetary Sciences under advisement of Dr. launched so it could be observed during a radar campaigns for NEOs that make close Amy Barr studying impact-induced processes on solid bodies. close flyby - about 69,000 from Earth. approaches to Earth (within ~0.05 AU) are roughly Spectral observations suggest that its surface equivalent in their science content to His current research focuses on two major areas, Solar System Formation and composition is similar to aubrites, a rare class flyby missions, but cost orders of magnitude less Evolution, and Astrobiology. Ed uses of high albedo differentiated meteorites. and more efficiently probe the overall population. observations paired with simulations to unravel the processes that led to the Indeed, the radar polarization ratio of >0.6 This study shows how radar data in tandem with formation of the icy moons of Jupiter and indicates 2016 TC25 is an E-Type asteroid (see other wavelengths can provide a richer Saturn as well as processes that drove the Figure), thus agreeing with the spectrally understanding of the NEO population. evolution of the interior rocky worlds. Additionally, he studies aqueous processes constrained composition. 2015 TC25 is also a on Mars in search for habitable abodes beyond Earth. He teaches every summer at the Alfred University Astronomy Institute for High School Students and at AO he is the Project Manager for the Arecibo Observatory Space Academy.

Power spectrum of asteroid 2015 TC25 from Arecibo radar showing Doppler Frequency on the X-axis and echo power on the Y-axis. The solid and dashed lines show echoes of each circular polarization. Combining the observations from the two panels suggests a polarization ratio of ~ 0.9. A value this high is indicative of E-type asteroids, which are thought to have surfaces composed primarily of enstatite (MgSiO3) achondrites. First Simultaneous Measurements of Na and K Thermospheric Layers along with TILs from Arecibo

Altitude vs. Time plots for neutral (a) K and (b) Na metals obtained using two different resonance lidars located at Arecibo; (c) the electron concentrations inferred using simultaneous Incoherent Scatter Radar data. The black lines superimposed on the contour plots show the descent rates of the neutrals (a, b) and Tidal Ions Layers (c).

Authors: Shikha Raizada, C. M. Brum, C. A. Tepley, Jens Lautenbach, J. S. Friedman, John D. Mathews, F. T. Djuth, and Caitlin Kerr

Paper Reference: Geophys. Res. Lett., 42, 10,106–10,112, doi:10.1002/2015GL066714.

Abstract: first time. These simultaneous lidar and ISR variability compared with other locations. The It is well known that metals are deposited in observations shown in the above figure observations of F-region descending layers the mesospheric region of the Earth’s revealed that the neutral layers descend at a using the world’s most sensitive ISR along with atmosphere through the ablation of much slower rate of ~0.69 ms-1 than the neutral layers observed using resonance meteors. These well-established main faster TILs with a rate of ~14.7 ms-1. We also lidars offer a new perspective about their layers occur between 80 and 105 km. investigated the neutralization lifetimes of origin and demands more observational work. However, recent observations of metals ions within TILs to test the previous Such efforts will help us understand the extending to higher altitudes have hypothesis and determine if they can be disintegration processes and intrigued the community as these occur generated through this mechanism. We latitude dependence. These studies will above the so called “meteor zone.” Previous demonstrated that, at these altitudes, ions enhance our knowledge of mass deposition in Chemical Ablation Models have shown that have very long lifetimes and their number the Earth’s atmosphere through exceeding 10-7 g can attain densities exceed the feasible values. Thus, extra-terrestrial space phenomena. ablation temperatures of 1800 K below 100 we determined that some other mechanism km, where volatile elements like Na and K involving a different meteoroid start to get released. Thus, previous lidar disintegration process needed to measurements attributed the occurrence be considered at thermospheric of thermospheric metals to be the result of altitudes and proposed that neutralization of the ions within the sputtering might be responsible Fast Radio burst descending layers, or Tidal Ion Layers (TILs) for the deposition of these seen at Arecibo, but simultaneous meteoric metals. Incoherent Scatter Radar (ISR) and lidar data were required to confirm or refute This new result required both the these theories. optical (resonance lidars) and ISR, a Fast Radio burst unique instrument cluster at In this paper, we utilize the unique Arecibo and not available Photo: LIDAR Lab at the Arecibo Observatory observational capabilities at Arecibo to elsewhere. In addition, Arecibo is a Arecibo Observatory houses the lidars to study atmospheric investigate the relationship between the TILs geographically low-latitude but temperatures and densities using Rayleigh and Resonance and thermospheric metals occurring at geo-magnetically mid-latitude site, lidars altitudes between 110 and 150 km for the so it has different ionospheric A Repeating Fast Radio Burst

Authors: Laura Spitler, Paul Scholz, Jason Hessels, Slavko Bogdanov, Adam Brazier, Fernando Camilo, Shami Chatterjee, Jim Cordes, Froney Crawford, Julia Deneva, Rob Ferdman, Paulo Freire, Vicky Kaspi, Patrick Lazarus, Ryan Lynch, Eric Madsen, Maura McLaughlin, Chitrang Patel, Scott Ransom, Andrew Seymour, Ingrid Stairs, Ben Stappers, Joeri van Leeuwen & Weiwei Zhu Paper Reference: 531, 202-205 (doi:10.1038/nature17168). Published 2016. ADS link: http://adsabs.harvard.edu/abs/2016Natur.531..202S

Abstract: In the last decade, radio telescopes have started to detect mysterious signals called “Fast Radio Bursts” (FRBs). The FRBs are radio flashes that last for only a few milliseconds; they have been discovered using the same techniques that have been employed for decades to search for radio pulsars. As with pulsar signals, we can estimate the distance to the FRB source based on how much later the signal arrives at low radio frequencies compared to higher radio frequencies – an effect that is caused by dispersion of the signal as it travels through the interstellar material between Earth and the source. Surprisingly, the inferred distances to the FRBs are huge: they imply that the sources must be well outside the Milky Way, and perhaps many hundreds of millions or even billions of light years from Earth. Another key aspect of the FRBs is that their signals have so far not repeated. With only one radio flash seen in any given sky direction, this suggests that the mechanism that produces the signal is cataclysmic in nature – i.e., a massive explosion like the collision of two neutron stars, which can only ever be seen once. Many theoretical The 305-m Arecibo telescope and its suspended support models have been developed to explain the FRB phenomenon, but their true nature platform of radio receivers is shown amid a starry night. remains a mystery, and one of the hottest topics of debate in Astronomy today. From space, a sequence of millisecond-duration radio

flashes are racing towards the dish, where they will be reflected and detected by the radio receivers. Such radio Arecibo is distinguished as being the second telescope, after Parkes, to discover an signals are called Fast Radio Bursts. Though this is an FRB. This source, called FRB121102 (based on the fact that it was detected Nov 2nd, artist’s conception, the bursts shown here are derived 2012) was published by Spitler et al. (2014) and generated a lot of excitement in the directly from the real data presented by Spitler et al. (2016). field. More recently, we continued monitoring FRB121102’s sky position in order to Figure Credit: Danielle Futselaar. test the hypothesis that the signal would never repeat. We were astounded, however, to discover that FRB121102 does repeat, albeit very sporadically. It is the first FRB to show such behavior. The simple fact that we have now detected multiple bursts from this source indicates that the origin of the signal cannot be a cataclysmic explosion. Rather, only theoretical models that can accommodate a repeating signal are viable; this includes super-giant pulses from a very young, extragalactic pulsar or outbursts from a hyper-magnetic neutron (a so-called “magnetar”). The discovery of repeated bursts from an FRB is thus a major breakthrough, though we are left with a new puzzle: do all FRBs sporadically repeat, or are there multiple types of FRB sources?

FRB121102 is an extremely weak radio source, and this discovery of repeated bursts was only possible because Arecibo provides the largest sensitivity of any single-dish on Earth. Fast Radio burst Fast Radio burst Fast Radio burst Fast Radio burst Fast Radio burst Fast Radio burst Fast Radio burst Fast Radio burst AN AMAZING JOB WELL DONE!

Miguel Nieves, Heriberto Toledo, Jose Chacon, Edwin Gonzalez, Joselito Diaz, Jose Anibal Rosado, Angel Millet, Christian Maldonado, Juan Rodriguez, Carmelo Sein, and Arturo Rodriguez. Not shown: Hiram Crespo and Jaime Gago. (Photo courtesy of telescope operator Israel Cabrera.)

It is our pleasure to introduce you to Arecibo Observatory’s platform crew. These guys sand blasted and painted the azimuth arm, preparing your telescope for the future. They worked for weeks: -500 ft in the air, -in a potentially toxic environment, -in the heat and humidity, -under a containment tarp, -wearing hazmat suits, -scrutinized by EPA inspectors.

The painting is complete, the tarp has been removed, and your telescope looks like its familiar old self, but with a shiny new coat of lead-free paint. This painting was essential to protect the telescope from rust and preserve the structure for the future. We want to thank the Observatory’s amazing platform crew for carrying out this vital work with skill and dedication - dodging the Puerto Rican rain storms throughout the process. We also thank our users for their patience and understanding while we undertook this complex project. Full motion of the telescope has been restored and observations have returned to normal

The Arecibo Observatory Science and Visitors Center reopens with new interactive exhibits

After 18 years, it was time for an upgrade. Thanks to the contributions from the Angel Ramos Foundation and the Ana G. Méndez University System, in 2015, the Visitors Center underwent a transformation. The physical renovations included new restroom facilities, a new entrance, and a new observation deck. The exhibit area was also renewed. The new exhibits are focused on the work done at The Arecibo Observatory promoting the expansion of knowledge in the areas of radio astronomy, atmospheric sciences and planetary studies, in a fun way. collision of two neutron stars, which can only ever be seen once. Many theoretical models have been developed to explain the FRB phenomenon, but their true nature remains a mystery, and one of the hottest topics of debate in Astronomy today.

Arecibo is distinguished as being the second telescope, after Parkes, to discover an FRB. This source, called FRB121102 (based on the fact that it was detected Nov 2nd, 2012) was published by Spitler et al. (2014) and generated a lot of excitement in the field. More recently, we continued monitoring FRB121102’s sky position in order to test the hypothesis that the signal would never repeat. We were astounded, however, to discover that FRB121102 does repeat, albeit very sporadically. It is the first FRB to show such behavior. The simple fact that we have now detected multiple bursts from this source indicates that the origin of the signal cannot be a cataclysmic explosion. Rather, only theoretical models that can accommodate a repeating signal are viable; this includes super-giant pulses from a very young, extragalactic pulsar or outbursts from a hyper-magnetic (a so-called “magnetar”). The discovery of repeated bursts from an FRB is thus a major breakthrough, though we are left with a new puzzle: do all FRBs sporadically repeat, or are there multiple types of FRB sources?

FRB121102 is an extremely weak radio source, and this discovery of repeated bursts was only possible because Arecibo provides the largest sensitivity of any single-dish radio telescope on Earth.

USRA AN AMAZING JOB Special Award

WELL DONE! On June 17 the Arecibo Observatory staff organized a What began as a passion of a handful of individuals, a musician, surprise recognition ceremony to Dr. Tapasi Ghosh. filmmaker, technologist, scientist and astronaut, has become a global movement by thousands to increase awareness and Miguel Nieves, Heriberto Toledo, Jose Chacon, Edwin Gonzalez, Joselito Diaz, Jose Anibal Rosado, education about asteroids. Supported by 22 global partners, Angel Millet, Christian Maldonado, Juan Rodriguez, Carmelo Sein, and Arturo Rodriguez. Dr. Tapasi Ghosh has led the VLBI effort at Arecibo for Not shown: Hiram Crespo and Jaime Gago. (Photo courtesy of telescope operator Israel Cabrera.) many years, notching up a number of achievements scores of international agencies, 72 space travelers from 12 nations, leaders in business and finance, parents and youth, such as the first trans-Atlantic eVLBI fringes in 2004, and Asteroid Day 2016 included hundreds of events on and around forming the largest synthesised telescope ever in 2012 June 30, 2016. Professor Stephen Hawking, who participated in with a baseline of 20 Earth diameters from Arecibo to the Starmus Festival, an Asteroid Day event, states that “One of the RadioAstron satellite. Dr. Ghosh's work has enabled the major threats to intelligent life in our universe is a high probability of an asteroid colliding with inhabitable .” “Our a number of critical VLBI experiments, including the goal is to dedicate one day each year to learn about asteroids, the result by Melis et al. (2014) in Science, which measured origins of our universe, and to support the resources necessary the distance to the Pleiades with unprecedented to see, track and deflect dangerous asteroids from Earth’s orbital accuracy and demonstrated that the measurement of path,” explains Dr. Brian May, astrophysicist, guitarist and ESA's Hipparcos satellite was in error. However, as is songwriter for QUEEN who co-founded Asteroid Day. “Asteroids are a natural disaster we know how to prevent.” This is the standard in the VLBI community, Dr. Ghosh's work to premise of Asteroid Day. Asteroid Day is held on the anniversary enable these experiments does not result in scientific of the largest asteroid impact of Earth in recorded history. On recognition in publications; it would therefore be highly June 30, 1908, a relatively small asteroid (40 meters) exploded appropriate for USRA to recognize her contributions to over Tunguska, , releasing the equivalent of 10-30 megatons of TNT, devastating an area of about 800 square miles, the continued success of Arecibo Observatory and the the size of any major metropolitan city. role it plays in VLBI worldwide. The Arecibo Observatory hosted a day long program for all of the Science and Visitors Center guests. Creating their own clay asteroid, making a crater and seeing its formation in slow motion, detecting the space rock in our interactive exhibits, touching a real asteroid and being able to see a Martian and a lunar rock were just a few of the amazing experiences people had at the Arecibo Observatory.

We also had a special video presentation by Dr. Edgard Rivera-Valentín, a staff planetary scientist at the Arecibo Observatory. Dr. Edgar Rivera-Valentín’s asteroid presentation was focused on: What are asteroids and what does the population look like?, what is the impact hazard and what would we do to prevent an impact? and The Arecibo Planetary Radar Program - What do we do to detect and characterize asteroids and how does that help.

From left to right - Robert Minchin, Tapasi Ghosh, Joan Schmelz and Chris Salter National Astronomy and Ionosphere Center The Arecibo Observatory

We would like to thank Susan Clark (Columbia Univ.), not only for the original story but also for the essential inspiration. Thanks also to our other authors, Shikha Raizada (Arecibo Obs.), Edgard Rivera-Valentin (Arecibo Obs.), and Jason Hessels (ASTRON) for putting together great articles, practically overnight. You can help with future issues of the AO Newsletter by saying, “Yes!” when we invite you to submit an article. Recommendations for future articles as well as suggestions on formatting and content are also most welcome. Many Thanks!

For More Information, Contact Us. We hope you’ve enjoyed this Route 625 Bo. Esperanza Arecibo, Puerto Rico

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[email protected] The AO Newsletter is published by The Arecibo Observatory. The Arecibo Observatory is operated by SRI International, USRA and UMET under a cooperative agreement with the National Science Foundation. Joan Schmelz ([email protected]), Editor; www.naic.edu Ricardo Correa ([email protected]), Graphics, Layout Design and Editor.