The field of view for Kepler’s telescope is set: a star-rich patch of sky in the constellations Cygnus and Lyra. Credit: NASA/Ames/JPL-Caltech
At first glance the picture seems unremarkable — perhaps these are fabric swatches forgotten in a display case, now covered with accumulated dust. The truth is more awe-inspiring: Each speck of “dust” is light from stars in a patch of sky spanning 100 square degrees, between the constellations of Cygnus and Lyra. More than 4.5 million stars are captured here in the first image from Kepler, NASA’s new spacecraft designed to find Earth-like planets. Look closely — chances are another planet quite like our own lurks somewhere in this expansive view. And though you can’t see it, eventually Kepler will.
Kepler has a single eye, a telescope linked to the largest camera ever launched into space. It will stare unblinking for at least 3.5 years at this one region of the heavens, watching 100,000 promising stars for any “transits” — minute dips in light caused by the periodic passage of orbiting planets. The field of view lies along the galactic plane of the Milky Way where radiant clouds of stars are clumped thickly, increasing the total number of stars observed and the chances of detecting more planets.
Three transiting planets are already known to exist in Kepler’s field of view. All are “hot Jupiters,” worlds similar in size to Jupiter or Neptune that orbit inhospitably close to their host stars. Though their official names don’t exactly roll off the tongue — TrES-2, HAT-P-7b, and HAT-P-11b — they’ll become very familiar to the mission’s scientists and engineers, who will use them to calibrate the spacecraft’s instruments. But since Kepler will take unmatched measurements of these planets, they might still be the sources of major discoveries — slight statistical fluctuations in the timing of their transits could hint at accompanying moons or other non-transiting planets in their star systems.
This first image is just one in a long series of milestones. David Koch, Kepler’s deputy principal investigator, recalls planning for the mission with his colleague William Borucki back in 1992. Nine years passed before NASA approved the mission; it took eight more to construct and launch the spacecraft. Now Koch, Borucki, and the rest of their team are in the midst of a task that will define their careers, working feverishly to “commission” Kepler, preparing it for its first scientific observations in early May. After this the spacecraft will begin finding potential planets at a rapid pace, but the public won’t hear about most of them right away.
“There’s quite a bit of follow-up observing that we have to do,” Koch says. “When you have a candidate there are a lot of potential reasons that it could be a false positive.” Each possible planet that emerges from the data must be vetted and confirmed by observations from large ground-based telescopes, most of which already have packed schedules and limited availability, creating a potential bottleneck for the announcement of any discoveries.
Koch has already waited nearly two decades for this moment to come; taking a few more years to validate what may be one of this age’s greatest discoveries — other Earth-like planets in our galaxy — seems only sensible. When the time comes, he’ll be prepared with a ready visual aid.
“For the past five years, I’ve had Kepler’s star field covering one whole wall of our conference room ceiling to floor, assembled from six Palomar sky survey plates,” he says. “I already have three push-pins in the pictures where the three known transiting planets are. Right now I’m using red ones because they’re hot Jupiters, but I’m hoping I can push in some nice ‘pale blue dots’ soon.”
Originally published April 23, 2009
