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Gemini Planet Imager

January 17, 2014

I was a child of the Space Race. I was nine when Sputnik 1 was launched on October 4, 1957. There wasn't a man in space until Yuri Gagarin's single orbit flight in Vostok 1 on April 12, 1961. However, every satellite launch was front page news in that three and a half year interval. Space was exciting, even without the human element.

I remember being one of many elementary school students watching televised coverage of the first few US manned space launches on a very small screen in the school auditorium. When I was in college, there were men walking on the Moon, but public interest quickly waned. Each Moon mission topped the others with items such as a Moon buggy, but it had become all too routine.

After a space shuttle servicing mission solved its initial focusing problem, the Hubble Space Telescope returned spectacular images from 1994 onwards. Some of these have an aesthetic quality; but many, such as the deep field image shown below, are important scientifically.

Figure captionAn example of a Hubble Space Telescope deep field image, a photograph of 3,000 distant galaxies focused through gravitational lensing by the foreground galaxy, Abell 2744. These galaxies appear as they were 12 billion years ago.

(Image: NASA, ESA, J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team, via the Space Telescope Science Institute.)[1]

However, just as for manned spaceflight, such images no longer generate much public interest. The human mind is wired to seek novelty, and when the novelty in one area wanes, we look somewhere else. The same was true for me, until the recent release of the first images from the Gemini Planet Imager of the Gemini South Telescope, located in Cerro Pachon, Chile (30.24073°S 70.73659°W). This telescope is part of the Gemini Observatory.[2-9]

The Gemini Planet Imager was designed to obtain high contrast images of extrasolar planets around nearby stars. It operates at near-infrared wavelengths for which the extrasolar planets will be bright, but the thermal emission from the Earth's atmosphere isn't too strong.

The Gemini Planet Imager was a huge, long-term collaboration of the American Museum of Natural History, the Dunlap Institute, the Gemini Observatory, the Herzberg Institute of Astrophysics, the Jet Propulsion Laboratory, Lawrence Livermore National Laboratory, the Lowell Observatory, the SETI Institute, The Space Telescope Institute, the University of Montreal, the University of California, Berkeley, the University of California, Los Angeles, the University of California, Santa Cruz, and the University of Georgia. The principal investigator of the project is Stanford University physicist, Bruce Macintosh, working at Lawrence Livermore National Laboratory for this project.[3]

Gemini Planet Imager mounted on the Gemini South TelescopeGemini Planet Imager mounted on the Gemini South Telescope, one of the world's largest telescopes at 26-feet/8-meters.[5]

The Imager, which is the size of a small automobile, is the collection of boxes at the base of the telescope.

Aside from the essential adaptive optics system, the Imager includes a coronagraph, a calibration interferometer, and a spectrograph.

(Gemini image.)

Nearly a thousand extrasolar planets have been detected, but most of these detections have been indirect, based on the slight wobble of their parent star as they orbit. Direct imaging is preferable, since it can be used to estimate a planet's size, temperature, gravity, and, perhaps, the composition of its atmosphere. Direct imaging is a challenge, since the light emitted by even a Jupiter-sized planet is a billion times fainter than its parent star, and planets orbit close to their stars.[3,5]

The Gemini Planet Imager is designed to detect extrasolar young gas giants, one million to one billion years in age. Such young planets retain heat from their formation, so they can be detected by their infrared emission in the wavelength range of 0.9 and 2.4 micrometers. The Gemini Planet Imager can also detect the components of their atmospheres. Since Earth-based observation is difficult, these is the only type of planet that it can see.[2,4-5]

Earth-based direct observation of such extrasolar planets is only possible because of adaptive optics. The Gemini Planet Imager is based on a MEMS deformable mirror, which removes atmospheric turbulence. The two centimeter-square deformable mirror is composed of 4,000 actuators, etched into silicon. It can adjust its shape with accuracy better than a nanometer a thousand times per second.[3] It corrects atmospheric turbulence sensed by another system component. Another device, called a coronagraph, blocks light from the parent star.

Gemini Planet Imager view of disk of dust orbiting the young star HR 4796AGemini Planet Imager view of disk of dust orbiting the young star HR 4796A.

The sharp edge of the ring, debris remaining from planet formation, is thought to be defined by an unseen planet.

The image contrast was increased through the use of polarization detection.

This image and others were released at the 223rd meeting of the American Astronomical Society.

(Via Lawrence Livermore National Laboratory.)

Says principal investigator, Bruce Macintosh,
"Even these early first-light images are almost a factor of 10 better than the previous generation of instruments. In one minute, we were seeing planets that used to take us an hour to detect."[2-4]
The plan for 2014 is a survey to scan 600 young stars to see whether these host similar giant planets. Long term plans are for a similar, satellite-based instrument capable of imaging smaller extrasolar planets.[2,4]

Gemini Planet Imager view of planet Beta Pictoris bGemini Planet Imager view of planet Beta Pictoris b, the small dot at the lower right side of this image.

Beta Pictoris b, a planet several times larger than Jupiter, is only ten million years old.

(Via Lawrence Livermore National Laboratory.)

References:

  1. Hubble's First Frontier Field Finds Thousands of Unseen, Faraway Galaxies, Space Telescope Institute Press Release No. STScI-2014-01, January 7, 2014.
  2. Gemini Planet Imager First Light!, Gemini Observatory Press Release, January 7, 2014.
  3. Anne M Stark, "Out of this world first light images emerge from Gemini Planet Imager," Lawrence Livermore National Laboratory Press Release No. NR-14-01-01, January 7, 2014.
  4. World's Most Powerful Planet Finder Turns its Eye to the Sky - Gemini Planet Imager Obtains First Light Images, SETI Institute Press Release, January 7, 2014.
  5. Whitney Clavin, "Powerful Planet Finder Turns Its Eye to the Sky," NASA JPL Press Release, January 7, 2014.
  6. Anne M Stark, "The search for planets and stars out of this world," LLNL news story, June 6, 2011.
  7. Gemini Planet Imager Web Site.
  8. Gemini Observatory Web Site.
  9. Gemini Planet Imager blog.

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