Gemini Planet Imager: New Telescope Will Photograph Distant Worlds

For those who wonder about alien worlds out there, this is an exciting time of discovery. The number of exoplanets found so far is now well into the thousands and rapidly growing. The one downside—if you can call it that—is that these planets, with just a few exceptions, have been discovered by methods other than direct imaging. So there are still precious few actual photos of any of these far-off worlds. But a new “extreme” telescope is set to start changing that.

The Gemini Planet Imager will take planet hunting to the next level, being able to image more planets than ever before. GPI is a telescopic instrument about the size of a small car designed to be attached to the 8-meter Gemini South telescope in Chile. It will use “extreme” adaptive optics to image the planets orbiting their stars.

Other large telescopes also use adaptive optics to compensate for the twinkling effect of stars due to Earth’s atmosphere, but GPI will use a mirror made from advanced silicon microelectromechanical systems (MEMS) rather than glass. The images it takes will be sharper than those obtained previously by other telescopes. At such distances, any planets, even large ones, are just tiny dots of light, but the new images will still be a significant improvement, and more planets will be able to be photographed. GPI is capable of imaging objects ten million times fainter than the parent star!

Being able to actually see some of these planets helps to illustrate that they really are out there, and that they are places and worlds in their own right. As astronomer Bruce Macintosh, principal investigator for GPI, puts it, “There’s something satisfying about seeing the little dot.”

GPI will also be able to analyze the light from the planets to determine their mass and composition, including size, temperature, gravity, and the composition of the atmosphere. This will aid scientists in learning just how similar, or different, our solar system is from others. The type of planets it will focus on are larger gas giants like Jupiter, with larger orbits around their stars. Younger and warmer “adolescent” planets will be the easiest to find. Unfortunately, GPI won’t be able to see Earth-sized planets or planets that have closer orbits to their stars. Still, the results will help astronomers better understand the overall structures of other solar systems. It is already known now from Kepler and other telescopes that many of these planetary systems have Earth-sized and even smaller planets, just like ours.

Astronomer Sara Seager of Massachusetts Institute of Technology sums it up this way: “For all we know, GPI could be the next Kepler. They’re bound to find many, many fascinating objects, because it’s a new eye on the sky.”

GPI is scheduled to start its science operations in October of this year.