Stellar Oddballs: Kepler Spacecraft Finds Much More Than Exoplanets

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After mind-bendingly precise data and artists' renditions of mysterious stars played across the screen, Martin Still leaned into his lectern at an American Association for the Advancement of Science meeting early this year to deliver a plea to fellow astronomers. In one word: Help!

"We need you guys," said the manager of NASA's guest observer program for Kepler, among the most successful space telescopes ever launched. "Wait a year and it's too late."

Kepler has found a bonus, a treasury of wonders, or one might say a stellar freak show out in space. The result is a predicament: This is not what the space telescope was looking for. Kepler's NASA team has one job that it must, by contract, pursue almost exclusively--hunting for extra-solar planets. In-house researchers must largely ignore other wonders. Hence the call for aid from guest observers, people given access to a telescope's data, but who typically provide their own resources to analyze the results and pursue more.

In science, new instruments routinely discover unexpected things. But Kepler's surprises--which could help astronomers learn far more about the evolution of stars, their internal structures and how the burning balls of plasma die--require fast action if they are to be fully examined.

The telescope honors 17th century German astronomer Johannes Kepler. He was first to realize that planets follow elliptical, not circular, orbits, and he established three laws of planetary motion. "Our mission is to find planets. We hope to find Earthlike planets," says the project's founder and principal investigator, William Borucki of NASA's Ames Research Center in Mountain View, Calif. Borucki spent decades fighting against great skepticism to build an orbiting instrument so sensitive it would detect planets that briefly cross, or transit, their stars' faces.

NASA launched the telescope in March 2009 into a "trailing" orbit. Sitting slightly farther from the sun than Earth does, Kepler makes one trip around the sun every 372 days, gradually falling farther behind Earth. In its solitude, the spacecraft keeps its eye on hordes of stars, checking for planets.

It is finding them, too, in scads. There are more than 1,200 entries on Kepler's list of candidate planets (SN: 2/26/11, p. 18) betrayed by small, repetitive and distinctively shaped dips in the brightness of their parent stars--the shadow of a planet crossing a star's face as seen by the craft. While further analysis surely will reveal some as false alarms, chances are that 90 percent are real. That will triple the number of known exoplanets. With time, scientists hope to confirm a few with Earthlike size, orbit and other conditions suitable for life as we know it to arise.

But the majority of stars don't have planets lined up to block light headed toward Kepler. These stars too are worthy of study. Still, who is based at Ames, hopes outside astronomers will take a close look at Kepler's new data on stars without signs of planets, plus look at those stars with other scientific instruments while the craft is still operational.

Eye for the weird

"There are so many stars that show bizarre, utterly unexplainable brightness variations that I don't know where to begin" says Geoff Marcy of the University of California, Berkeley. Marcy gained fame in the mid-1990s when he helped pioneer, with ground-based instruments, discovery of extrasolar planets; he joined the Kepler team to help expand the planet-finding toolbox. After the detection of far more than planets began overwhelming the Kepler program, Marcy hired an undergraduate statistics major to scan the plots of varying brightness for tens of thousands of stars. He trained her to spot what Marcy calls the WTF objects, which might politely be rendered "What The Flip is that?"

Astronomers have already spotted stars with remarkable pulsation modes, double stars orbiting so closely that streams of white-hot plasma flow between them, immense star spots whose movements hint at unlikely rotations, collapsed white dwarf stars in eclipsing orbits around large and seemingly younger stars, and more. …