AO Newsletter May-June 2016 [English vol1]

T h e

A r e c i b o

O b s e r v a t o r y

Newsletter M a y - J u n e

2 0 1 6

Highlights Galaxy Neutral Hydrogen Structures Trace Dust Polarization Angle: Implications for Cosmic Microwave Background Foregrounds

Welcome to our AO Newsletter, our AO Newsletter celebrates the new, fundamental, cutting-edge science done at the Arecibo Observatory. A relaunch of the newsletter has been a recommendation of our Users Committee, but it was hard to do with a scientific staff that has been described as a “skeleton crew.” As I was struggling to find a way to implement this recommendation, I was inspired

Asteroids Physical Characterization of ~2-meter Diameter Near-Earth Asteroid 2015 TC25: A possible boulder from E-type Asteroid (44) 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 amount of sub-discipline specific jargon, and it had a cool picture! In short, it would make the perfect newsletter article. I realized that we could indeed

Atmosphere First Simultaneous Measurements of Na and K Thermospheric Layers along with TILs 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

Observatory. I hope the discoveries inspire you as much as they inspire me.

- Joan Schmelz, Arecibo Observatory and USRA

Fast Radio Burst 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

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 the Big Bang, the Universe is thought to have experienced a growth spurt – a period of rapid expansion known as inflation.

Cosmological observations provide strong circumstantial evidence for inflation, but no direct detection thus far. The predicted "smoking gun" evidence for inflation is primordial B-mode polarization. These “B-modes” are a polarization pattern imprinted in the cosmic microwave background (CMB), the pervasive leftover radiation from the Universe’s formation.

Unfortunately, despite enormous experimental effort, the B-mode signal has yet to be detected because it is obscured by polarized dust in our galaxy. Galactic dust grains emit polarized light because they are aligned with the interstellar magnetic field, creating a signal that must be carefully measured and subtracted from CMB data in order to uncover the inflationary B-mode signal.

This dust is a component of the interstellar medium – all the

diffuse material between the stars in the Milky Way. The interstellar medium is also full of gas, much of which is neutral hydrogen. Here, we present the discovery that slender linear filaments of neutral hydrogen gas in the Milky Way, revealed by high-resolution Arecibo survey data, are extremely well aligned with the dust polarization.

This means that structures in the gas are strongly aligned with the ambient magnetic field. We use a machine vision algorithm to measure the orientation of the Arecibo filaments. The shape of neutral hydrogen provides an entirely new way to constrain the dust polarization foreground obscuring the inflationary B-mode signal.

Our work will allow astrophysicists to more precisely measure the foreground dust signal, improving our ability to uncover the signature of inflation.

This work would not have been possible without Arecibo. The sensitive, high dynamic range Galactic Arecibo L-Band Feed Array (GALFA) HI Survey revealed the slender, magnetically aligned neutral hydrogen structures.

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.

Abstract: Small bodies in the solar system are time capsules that have recorded the conditions during planet formation. Studying these objects will not only help us better understand how our planet formed, but also how large impacts help shape the course of life on Earth. The Chelyabinsk bolide that entered Earth's atmosphere over Russia in 2013 reminds us of the threats posed by small near-Earth asteroids (NEAs) with diameters <20 meters. Furthermore, small NEAs are the progenitors for meteorites in our terrestrial collection. The physical characteristics of these small NEAs are crucial to our understanding of the effectiveness of our atmosphere in filtering these low-strength impactors, but characterization has been a challenge because of the difficulty in detecting them prior to close Earth flyby.

NEA 2015 TC25 was first observed on October 11, 2015 and a quick response campaign was launched so it could be observed during a close flyby - about 69,000 miles from Earth.

Spectral observations suggest that its surface composition is similar to aubrites, a rare class of high albedo differentiated meteorites.

Indeed, the radar polarization ratio of >0.6 indicates 2016 TC25 is an E-Type asteroid (see Figure), thus agreeing with the spectrally constrained composition. 2015 TC25 is also a

very fast rotator with a period of 133 seconds. We compared spectral and dynamical properties of 2015 TC25 and found the best candidate source body in the inner main belt to be the 70-km diameter E-type asteroid (44) Nysa. Using the albedo of E-type asteroids (50-60%), we refine the diameter of 2015 TC25 to 2-meters making it one of the smallest NEAs ever to be characterized and the smallest NEA ever detected by the Arecibo radar.

The Arecibo Observatory planetary radar system, which is funded through NASA’s Near-Earth Object Observation Program, provides crucial information for the assessment of impact hazards from near-Earth objects, as well as invaluable information on the object’s size, shape, mass, spin, and constraints on the composition. Such characterization further refines the orbit determination, extending predictions by 80 to 400 years compared to single-apparition optical measurements. Indeed, radar campaigns for NEOs that make close approaches to Earth (within ~0.05 AU) are roughly equivalent in their science content to spacecraft flyby missions, but cost orders of magnitude less and more efficiently probe the overall population.

This study shows how radar data in tandem with other wavelengths can provide a richer understanding of the NEO population.

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.

Know our staff Edgard Rivera-Valentín, a native of Arecibo Puerto Rico, is a staff planetary scientist at the Arecibo Observatory. In 2008, he earned a bachelor's degree in Physics and Mathematics at Alfred University, where he also minored in planetary science, a program he pioneered and helped build at Alfred. In the summer of 2007, he had the opportunity to participate in the Lunar and Planetary Institute’s REU program, where he worked with Drs. Michelle Kirchoff and Paul Schenk on impact cratering of Jupiter’s icy moons.

He went on to the University of Arkansas for his graduate studies where in 2012 he 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, Solar System 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 Saturn as well as processes that drove the evolution of the interior rocky worlds.

Additionally, he studies aqueous processes 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.

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: It is well known that metals are deposited in the mesospheric region of the Earth’s atmosphere through the ablation of meteors. These well-established main layers occur between 80 and 105 km.

However, recent observations of metals extending to higher altitudes have intrigued the community as these occur above the so called “meteor zone.” Previous Chemical Ablation Models have shown that meteoroids exceeding 10-7 g can attain ablation temperatures of 1800 K below 100 km, where volatile elements like Na and K start to get released. Thus, previous lidar measurements attributed the occurrence of thermospheric metals to be the result of neutralization of the ions within the descending layers, or Tidal Ion Layers (TILs) seen at Arecibo, but simultaneous Incoherent Scatter Radar (ISR) and lidar data were required to confirm or refute these theories.

In this paper, we utilize the unique observational capabilities at Arecibo to investigate the relationship between the TILs and thermospheric metals occurring at altitudes between 110 and 150 km for the

first time. These simultaneous lidar and ISR observations shown in the above figure revealed that the neutral layers descend at a much slower rate of ~0.69 ms-1 than the faster TILs with a rate of ~14.7 ms-1. We also investigated the neutralization lifetimes of ions within TILs to test the previous hypothesis and determine if they can be generated through this mechanism. We demonstrated that, at these altitudes, ions have very long lifetimes and their number densities exceed the feasible values. Thus, we determined that some other mechanism involving a different meteoroid disintegration process needed to be considered at thermospheric altitudes and proposed that sputtering might be responsible for the deposition of these meteoric metals.

This new result required both the optical (resonance lidars) and ISR, a unique instrument cluster at Arecibo and not available elsewhere. In addition, Arecibo is a geographically low-latitude but geo-magnetically mid-latitude site, so it has different ionospheric

variability compared with other locations. The observations of F-region descending layers using the world’s most sensitive ISR along with neutral layers observed using resonance lidars offer a new perspective about their origin and demands more observational work.

Such efforts will help us understand the meteoroid disintegration processes and latitude dependence. These studies will enhance our knowledge of mass deposition in the Earth’s atmosphere through extra-terrestrial space weather phenomena.

Fast R

Fast Radio b

Photo: LIDAR Lab at the Arecibo Observatory Arecibo Observatory houses the lidars to study atmospheric temperatures and densities using Rayleigh and Resonance lidars

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: Nature 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 The 305-m Arecibo telescope and its suspended support platform of radio receivers is shown amid a starry night.

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 signals are called Fast Radio Bursts. Though this is an artist’s conception, the bursts shown here are derived directly from the real data presented by Spitler et al. (2016).

Figure Credit: Danielle Futselaar.

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 neutron star (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.

Fast Radio burst Radio burst Fast Radio burst Fast Radio burst burst Fast Radio burst Fas

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 the heat and humidity, -wearing hazmat suits,

-in a potentially toxic environment, -under a containment tarp, -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.

U S R A Special Award On June 17 the Arecibo Observatory staff organized a surprise recognition ceremony to Dr. Tapasi Ghosh.

Dr. Tapasi Ghosh has led the VLBI effort at Arecibo for many years, notching up a number of achievements such as the first trans-Atlantic eVLBI fringes in 2004, and forming the largest synthesised telescope ever in 2012 with a baseline of 20 Earth diameters from Arecibo to the RadioAstron satellite. Dr. Ghosh's work has enabled a number of critical VLBI experiments, including the result by Melis et al. (2014) in Science, which measured the distance to the Pleiades with unprecedented accuracy and demonstrated that the measurement of ESA's Hipparcos satellite was in error. However, as is standard in the VLBI community, Dr. Ghosh's work to enable these experiments does not result in scientific recognition in publications; it would therefore be highly appropriate for USRA to recognize her contributions to the continued success of Arecibo Observatory and the role it plays in VLBI worldwide.

What began as a passion of a handful of individuals, a musician, filmmaker, technologist, scientist and astronaut, has become a global movement by thousands to increase awareness and education about asteroids. Supported by 22 global partners, scores of international agencies, 72 space travelers from 12 nations, leaders in business and finance, parents and youth, Asteroid Day 2016 included hundreds of events on and around June 30, 2016. Professor Stephen Hawking, who participated in the Starmus Festival, an Asteroid Day event, states that “One of the major threats to intelligent life in our universe is a high probability of an asteroid colliding with inhabitable planets.” “Our goal is to dedicate one day each year to learn about asteroids, the origins of our universe, and to support the resources necessary to see, track and deflect dangerous asteroids from Earth’s orbital path,” explains Dr. Brian May, astrophysicist, guitarist and songwriter for QUEEN who co-founded Asteroid Day. “Asteroids are a natural disaster we know how to prevent.” This is the premise of Asteroid Day. Asteroid Day is held on the anniversary of the largest asteroid impact of Earth in recorded history. On June 30, 1908, a relatively small asteroid (40 meters) exploded over Tunguska, Siberia, releasing the equivalent of 10-30 megatons of TNT, devastating an area of about 800 square miles, the size of any major metropolitan city.

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

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rcorrea@naic.edu 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 (jschmelz@usra.edu), Editor; Ricardo Correa (rcorrea@naic.edu), Graphics, Layout Design and Editor.

www.naic.edu