The search for planets and stars out of this world

Jun. 3, 2011

The moon rises over Gemini Observatory South on Cerro Pachon, Chile. Image courtesy Gemini Observatory . (Download Image)

The search for planets and stars out of this world

There are a lot of things someone could do in nearly 900 hours.

Bruce Macintosh and his team plan to look for things that are out of this world, specifically 600 stars and up to 50 new planets.

Macintosh, a scientist in the Lab's Institute for Geophysics and Planetary Physics, and an international Gemini Planet Imager (GPI) Science Team have won an 890-hour observing campaign to use the GPI instrument to detect and image extra-solar planets.

The Gemini Planet Imager is the next generation adaptive optics instrument being built for the Gemini Telescope, with an 8-meter diameter mirror located on Cerro Pachon (Chilean Andes) an altitude of 9,000 feet. The GPI goal is to image extrasolar planets orbiting nearby stars. LLNL has been building GPI for five years - the allocation of the campaign time means that Macintosh and his collaborators will be the people who get to use the product of their labors.

"We want to directly detect the light from extrasolar planets to determine their mass and composition with the ultimate goal of determining the origin of our own planetary system," Macintosh said.

The team plans to use GPI I to produce the first-ever robust census of giant planet populations in the 5-50 AU (astronomical unit - one astronomical unit is approximately the distance from the Earth to the Sun) range from their parent stars. The stars are many light years away from Earth, Macintosh said. .

"We hope to discover about 50 exoplanets, increasing the number of exoplanet images by an order of magnitude," Macintosh said.

The Laboratory has a long history of developing adaptive optics systems with the first ever being installed at the Lick Observatory on Mt. Hamilton and next generation systems installed at the Keck Observatory in Hawaii. At Gemini, a Livermore team is in the process of creating advanced adaptive optics using silicon microchip deformable mirrors to remove atmospheric turbulence, and coronagraphic masks to block the diffracted light from the parent star. The system is expected to ship to Chile early next year. It will be able to see objects ten million times fainter than their parent star.

More than 500 extrasolar planets have been found to date, but mostly through indirect Doppler techniques that indicate the planet's mass and orbit. By using GPI, the team can pick out a planet from its star's glare, measure the planet's size, temperature, gravity and composition of its atmosphere using spectroscopy.

"By targeting many stars, we will be able to understand how common or unusual our own planetary system may be," Macintosh said.

The 890 hours of viewing time is the largest amount of time allocated to one group at Gemini. It will represent about 10 percent of the telescope time for three years.

Goals include: illuminate the formation pathways of Jovian planets; reconstruct the early dynamical evolution of systems, including migration mechanisms and the interaction with disks and belts of debris; and bridge the gap between Jupiter-sized planets and brown dwarfs with the first examples of cool, low-gravity planetary atmospheres.