ALMA image of dusty cometary ring around HR 8799, the only star where multiple planets have been imaged. The new data suggest the planets either migrated or another undiscovered planet is present. The zoom-in portion of the image, taken with ESO's Very Large Telescope, shows the location of the known planets in this system in relation to a graphical representation of the central star. Credit: Booth et al., ALMA (NRAO/ESO/NAOJ); A. Zurlo, et al.
VLBA image of Compact Symmetric Object J13262+3152, called "an archetypical example" of such an object.
Credit: Tremblay, et al., NRAO/AUI/NSF
Patent for surface treatment for self-calibrating radiometer awarded to NRAO engineer Galen Watts.
Credit: NRAO/AUI/NSF
NRAO engineers Tod Boyd and Matt Morgan, recipients of the 2015 IEEE Antenna
and Propagation Society Harold A. Wheeler Applications Prize Paper
Award. Credit: NRAO/AUI/NSF
1. Cometary Belt around Distant Multi-planet System Hints at Hidden or Wandering Planets
Astronomers
using the Atacama Large Millimeter/submillimeter Array (ALMA) have made
the first high-resolution image of the cometary belt (a region
analogous to our own Kuiper belt) around HR 8799, the only star where
multiple planets have been imaged directly. The shape of this dusty
disk, particularly its inner edge, is surprisingly inconsistent with the
orbits of the planets, suggesting that either they changed position
over time or there is at least one more planet in the system yet to be
discovered. "These data really allow us to see the inner edge of this
disk for the first time," explains Mark Booth from Pontificia
Universidad Católica de Chile and lead author of the study. "By studying
the interactions between the planets and the disk, this new observation
shows that either the planets that we see have had different orbits in
the past or there is at least one more planet in the system that is too
small to have been detected." The disk, which fills a region 150 to 420
times the Sun-Earth distance, is produced by the ongoing collisions of
cometary bodies in the outer reaches of this star system. ALMA was able
to image the emission from millimeter-size debris in the disk; according
to the researchers, the small size of these dust grains suggests that
the planets in the system are larger than Jupiter. Previous observations
with other telescopes at shorter wavelengths did not detect this
discrepancy in the disk. It is not clear if this difference is due to
the low resolution of the previous observations or because different
wavelengths are sensitive to different grain sizes, which would be
distributed slightly differently. HR 8799 is a young star approximately
1.5 times the mass of the Sun located 129 light-years from Earth in the
direction of the constellation Pegasus. "This is the very first time
that a multi-planet system with orbiting dust is imaged, allowing for
direct comparison with the formation and dynamics of our own Solar
System," explains Antonio Hales, co-author of the study from the
National Radio Astronomy Observatory in Charlottesville, Va. The
astronomers are reporting their results in the Monthly Notices of the Royal Astronomical Society.
Reference: "Resolving
the Planetesimal Belt of HR 8799 with ALMA," Booth et al.; Monthly
Notices of the Royal Astronomical Society [http://dx.doi.org/10.1093/mnrasl/slw040], May 2016. Preprint: http://arxiv.org/abs/1603.04853
2. VLBA Study Doubles Sample of Youngest Radio Galaxies
Astronomers
using the National Science Foundation's Very Long Baseline Array (VLBA)
have found 15 new examples of a rare type of object that may yield
valuable clues about how radio-emitting galaxies and their environments
evolve in their early stages of development. The objects, called compact
symmetric objects (CSOs), are small, young versions of the supermassive
black hole-powered "engines" that propel fast-moving jets of material
outward from radio galaxies. Following up on a large-scale VLBA survey
done in 2006, the scientists made more-detailed observations of objects
they identified as possible CSOs. Of 103 such candidates, they confirmed
24, 15 of which are newly identified as CSOs. Using McDonald
Observatory's Hobby-Eberly Telescope, they determined distances to some
of the objects, which allowed them to measure the objects' sizes. "This
doubles the number of these objects known," said Steven Tremblay, of
Curtin University in Australia. Enlarging the sample of known CSOs, the
astronomers said, can be a big help to understanding radio galaxies in
general. With sizes as small as 5 light-years across, and ages from only
20 to 2,000 years, CSOs represent an important early stage in the
development of the much larger and older radio-emitting galaxies. Even
at this early stage, the scientists said the CSOs in their sample show a
distinction between higher-powered and lower-powered objects that also
typifies older radio galaxies. "Understanding these young objects is
vital to understanding their larger cousins," said Greg Taylor, of the
University of New Mexico. The astronomers are reporting their results in
the Monthly Notices of the Royal Astronomical Society.
Reference:
"Compact Symmetric Objects and Supermassive Binary Black Holes in the
VLBA Imaging and Polarimetry Survey," Tremblay et al.; Monthly Notices
of the Royal Astronomical Society, May 2016. Preprint: http://arxiv.org/abs/1603.03094
3. Innovation from NRAO Engineer Yields New Patent
Galen
Watts, an engineer at the National Radio Astronomy Observatory's Green
Bank Microwave Electronics Group, received a patent (U.S. Patent Number:
9,343,815) for a surface treatment application for radiometers that
aids in their self-calibration. Radiometers are devices that measure the
actual energy of microwaves and other forms of electromagnetic
radiation. Radio astronomers and other researchers use microwave
radiometry to discover the molecular and atomic composition as well as
the temperature of many objects on Earth and even the most distant
celestial objects. They do this by examining the content of these
objects’ naturally emitted microwave signals. To make accurate readings,
however, a radiometer has to be properly calibrated. The new surface
treatment application, developed by Watts, aids in radiometer
self-calibration by reflecting an image of the feed horn back onto
itself in a manner that doesn't set up standing waves. Similar
applications could also be useful for reducing antenna side-lobes
(extraneous readings in radio astronomy), reducing radar cross-sections
of objects, and eliminating resonances from stray reflections in
quasi-optical component assemblies.
4. NRAO Engineers Receive IEEE Antenna and Propagation Society Award
NRAO
engineers Mathew A. Morgan and Tod A. Boyd have been awarded jointly
the 2015 IEEE Antenna and Propagation Society Harold A. Wheeler
Applications Prize Paper Award, which is presented to the authors of the
best applications paper published in the IEEE Transactions on Antennas and Propagation
during the previous year. Their paper, "A 10-100 GHz Double-Ridged Horn
Antenna and Coax Launcher," was published in August 2015 and reports on
the development of a novel radio antenna. It is described as an
ultra-wideband, double-ridged horn antenna with a bandwidth that covers a
ten-fold range in frequencies. This is believed to be the first such
decade-bandwidth horn in the millimeter-wave frequency range, covering
-- in this case -- 10-100 GHz. Such horns can be used for test and
measurement applications, including material characterization. It was
originally designed as a scale model for an even higher-frequency horn
covering 100 GHz - 1 THz. For this award, they will each receive a
certificate and share in the $1,000 honorarium. The award will be
presented at the IEEE APS/URSI Symposium Awards Ceremony, June 29, 2016,
in Fajardo, Puerto Rico.
The National Radio Astronomy
Observatory is a facility of the National Science Foundation, operated
under cooperative agreement by Associated Universities, Inc.
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KASI (Republic of South Korea), in cooperation with the Republic of
Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ.
Charles Blue, Public Information Officer
(434) 296-0314; cblue@nrao.edu
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