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
Newsletter
Route 625 Bo. Esperanza
Arecibo, Puerto Rico
(787) 878-2612
[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;
Ricardo Correa ([email protected]), Graphics, Layout Design and Editor.
www.naic.edu