Gemini Planet Imager: Powerful exoplanet camera turns skyward

Gemini Planet Imager's first light image of Beta Pictoris b, a planet orbiting the star Beta Pictoris. 

The star, Beta Pictoris, is blocked in this image by a mask so its light doesn't interfere with the light of the planet. 

In addition to the image, GPI obtains a spectrum from every pixel element in the field of view to allow scientists to study the planet in great detail. 

Beta Pictoris b is a giant planet – several times larger than Jupiter -- and is approximately ten million years old. 

These near-infrared images (1.5-1.8 microns) show the planet glowing in infrared light from the heat released in its formation. 

The bright star Beta Pictoris is hidden behind a mask in the center of the image. 

Credit: Processing by Christian Marois, NRC Canada.

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.

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 are seeing planets that used to take us an hour to detect," says Bruce Macintosh of the Lawrence Livermore National Laboratory who led the team that built the instrument.

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.

"Most planets that we know about to date are only known because of indirect methods that tell us a planet is there, a bit about its orbit and mass, but not much else," says Macintosh.

"With GPI we directly image planets around stars – it's a bit like being able to dissect the system and really dive into the planet's atmospheric makeup and characteristics."

Stephen Goodsell

GPI carried out its first observations last November – during an extremely trouble-free debut for an extraordinarily complex astronomical instrument the size of a small car.

"This was one of the smoothest first-light runs Gemini has ever seen" says Stephen Goodsell, who manages the project for the observatory.

This is Gemini Planet Imager's first light image of the light scattered by a disk of dust orbiting the young star HR4796A. 

This narrow ring is thought to be dust from asteroids or comets left behind by planet formation; some scientists have theorized that the sharp edge of the ring is defined by an unseen planet.

The left image (1.9-2.1 microns) shows normal light, including both the dust ring and the residual light from the central star scattered by turbulence in the Earth's atmosphere. 

The right image shows only polarized light. Leftover starlight is unpolarized and hence removed from this image. 

The light from the back edge of the disk is strongly polarized as it scatters towards us.

Credit: Processing by Marshall Perrin, Space Telescope Science Institute.

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 first-light 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.