What is GPI? A video describing the GPI project and recent results obtained with the instrument
Credit: F. Marchis, D. Futselaar, H. Marchis. Download Video
The Gemini Planet Imager Exoplanet Survey (GPIES) is an ambitious
three-year study dedicated to imaging young Jupiters and debris disks
around nearby stars using the GPI instrument installed on the Gemini
South telescope in Chile. On November 12, at the 47th annual meeting of
the AAS’s Division for Planetary Sciences in Washington DC, Franck
Marchis, Chair of the Exoplanet Research Thrust of the SETI Institute
and a scientist involved in the project since 2004, will report on the
status of the survey, emphasizing some discoveries made in its first
year.
Led by Bruce Macintosh from Stanford University, the survey began a year
ago and has already been highly successful, with several findings
already published in peer-reviewed journals.
“This very large survey is observing 600 young stars to look for two
things: giant planets orbiting them and debris disks. In our first year,
we have already found what GPI was designed to discover — a young
Jupiter in orbit around a nearby star,” said Marchis. This discovery
was announced in an article published in Science on Oct. 28 2015 with an
impressive list of eighty-eight co-authors from thirty-nine
institutions located in North and South America. “This is modern
astronomy at its best,” said Marchis. “These large projects gather
energy and creativity from many groups of researchers at various
institution, enabling them to consider different strategies to improve
the on-sky efficiency of the instrument and its scientific output.”
The survey was officially launched in November 2014. Eight observing
runs allowed the study of approximately 160 targets, or a quarter of the
sample. Other parts of the survey are more frustrating, though. Due to
the incipient El Nino, weather in Chile is worse than expected, with
clouds, rain, snow, and atmospheric turbulence too severe even for GPI
to fix. Since late June, out of the last 20 nights that team members
have spent at the telescope, they’ve only gotten a few hours of good
quality data. Despite this loss, over which the team of course had no
control, they have already published ten peer-reviewed papers in the
last year. Two of the findings are described below.
GPI data has revealed that 51 Eri b, the recently discovered
Jupiter-like exoplanet around the nearby star 51 Eridani, indeed has an
atmosphere of methane and water, and likely has a mass twice that of
Jupiter. The team has continued to observe this planetary system, and
observations recorded on Sept. 1, 2015 are most consistent with a planet
orbiting 51 Eri and not a brown dwarf passing along our line of sight.
“Thanks to GPI's incredible precision, we can demonstrate that the odds
are vanishingly small that 51 Eri b is actually a brown dwarf that has a
chance alignment with this star. In fact it's five times more likely
that I'll be struck by lightning this year than future data will show
this is not a planet orbiting 51 Eri” said Eric Nielsen, a postdoctoral
scholar at the SETI Institute and one of the authors of the paper
recently accepted for publication in The Astrophysical Journal Letters.
Another author of this study, SETI Research Experience for Undergrads
student Sarah Blunt, analyzed the motion of 51 Eri b and found it to be
completely consistent with a planet on an approximately 40-year orbit
around its host star.
The team has also discovered and imaged disks of dusty debris around
several stars. Astronomers believe that these are planetary systems that
are still forming their planets. Some have complex structures because
they host planets and fragments of the asteroidal and cometary materials
that formed those planets. One such system is HD 131835: a massive 15
Myr-old star located 400 light-years from Earth. Using GPI’s
high-contrast capability, the team imaged this disk for the first time
in near-infrared light in May 2015.
“The disk shows different morphology when observed in different
wavelengths. Unlike the extended disk previously imaged in thermal
emission, our GPI observations show a disk that has a ring-like
structure, indicating that the large grains are distributed differently
from the small ones. In addition, we discovered an asymmetry in the disk
along its major axis. What causes this disk to be asymmetric is the
subject of ongoing investigation, “ said Li-Wei Hung, a graduate student
in the UCLA Department of Physics and Astronomy and lead author of the
article submitted to The Astrophysical Journal Letters. As asymmetries
like the one seen in the system may be due to the gravitational
influence of an unseen planet, more detailed observational study could
one day confirm its existence.
As the GPIES survey enters in its second year, we are collaborating with
the Gemini Observatory to continue to improve the instrument. The
Gemini South telescope primary mirror was recently re-coated with silver
to improve reflectivity, and the GPI instrument was equipped with a new
cooling system to optimize performance.
“Continued collaboration between the Gemini Observatory and the GPIES
collaboration has worked really well - we’re learning a lot about how it
performs in the field and interacts with the atmosphere, and are
working to make GPI an even a better instrument to see even fainter and
closer planets,” said Bruce Macintosh, principal investigator of the
project and professor at Stanford University.
Media Contacts:
-
Peter Michaud
Public Information and Outreach
Gemini Observatory, Hilo, HI
Email: pmichaud@gemini.edu
Cell: (808) 936-6643
-
Seth Shostak
SETI Institute
Email: sshostak@seti.org
Phone: +1-650-960-4530
Science Contacts:
- Franck Marchis
SETI Institute
Email: fmarchis@seti.org
Phone: +1-510-599-0604
- Eric Nielsen
SETI Institute
Email: enielsen@seti.org
Phone: +1-408-394-4582
- Li-Wei Hung
University of California, Los Angeles
Email: liweih@astro.ucla.edu
Phone: +1 310-794-5582
Source: Gemini Observatory
