January 7, 2014
After nearly a decade of development, construction and testing, the world’s most advanced instrument for directly imaging and analyzing planets around other stars is pointing skyward and collecting light from distant worlds.
The instrument, called the Gemini Planet Imager (GPI), was designed, built and optimized for imaging faint planets next to bright stars and probing their atmospheres. It will also be a powerful tool for studying dusty, planet-forming disks around young stars. It is the most advanced such instrument to be deployed on one of the world’s biggest telescopes – the 8-meter Gemini South telescope in Chile.
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Jennifer Patience, an astrophysicist and associate professor in the School of Earth and Space Exploration at Arizona State University, has been working with the GPI team for almost 10 years. Her involvement began with contributions to the science case when the project was in the proposal stage, followed by a large scale effort to develop a set of ideal target stars around which to search for planets. Most recently, Patience and her students have been working with the GPI commissioning team on the initial data to help calibrate the instrument and ensure the best performance of the instrument.
Eyes to the sky
Exoplanets are extraordinarily faint and difficult to see next to a bright star. GPI can see planets a million times fainter than their parent stars. GPI detects infrared (heat) radiation from young Jupiter-like planets in wide orbits around other stars, those equivalent to the giant planets in our own Solar System, not long after their formation. Every planet GPI sees can be studied in detail.
GPI, an extraordinarily complex astronomical instrument the size of a small car, carried out its first observations last November. Patience and her students worked from ASU with analysis of the initial data taken in November and December.
For GPI’s first observations, the team targeted previously known planetary systems, including the well-known Beta Pictoris system; in it, GPI obtained the first-ever spectrum of the very young planet Beta Pictoris b. The team also used the instrument’s polarization mode – which can detect starlight scattered by tiny particles – to study a faint ring of dust orbiting the very young star HR4796A. With previous instruments, only the edges of this dust ring (which may be the debris remaining from planet formation) could be seen, but with GPI astronomers can follow the entire circumference of the ring.
Although GPI was designed to look at distant planets, it can also observe objects in our Solar System. The accompanying test images of Jupiter’s moon Europa, for example, can allow scientists to map changes in the satellite’s surface composition. The images were released today at the 223rd meeting of the American Astronomical Society in Washington, D.C.
“The early science images from GPI are spectacular and are an indication of the discoveries to come from the planet search survey that will commence this year. The ability to both image planets and investigate their atmospheres with a spectrum from GPI is a very exciting combination,” says Patience.
In 2014, the GPI team will begin a large-scale survey, looking at 600 young stars to see what giant planets orbit them. GPI will also be available to the whole Gemini community for other projects, ranging from studies of planet-forming disks to outflows of dust from massive, dying stars. Patience is one of two co-leads for developing the 600-star target list for this upcoming planet search survey.
“My research group and I are looking forward to the upcoming planet search survey. We will use GPI to discover new planets and learn how common giant planets are around stars of different masses and stars that are encircled by dusty disks analogous to the Kuiper belt in the Solar System. Since GPI is both a camera and a spectrograph, we will be able to investigate the atmospheres of detected planets and begin to characterize these other worlds,” explains Patience.
Looking through Earth’s turbulent atmosphere, even with advanced adaptive optics, GPI will only be able to see Jupiter-sized planets. But similar technology is being proposed for future space telescopes, and instruments like GPI are paving the way for a future instrument to image Earth-like planets.
For more information on GPI visit: http://planetimager.org/.