NASA announced that its Kepler telescope has verified 1,284 exoplanets in our galaxy, more than doubling the number of known planets orbiting other stars. An additional 1,327 candidates have better-than-even odds of being actual planets, but they aren’t well enough substantiated to be called “verified,” and will require additional study. What’s more, Kepler reports nine confirmed exoplanets of Earth-like size in their star’s Goldilocks zone.
At the core of Kepler’s ability to say it has found planets lie its methods of prediction and verification. Kepler finds planets by watching for stellar dimming: When a planet passes between its star and an observer, the star gets a little dimmer for a little while. This works fine as long as you can find planets that pass directly between their parent stars and our telescopes, but it’s failed in the past, because planets aren’t the only things that can dim a star’s light. Binary stars or smaller, dimmer stars called brown dwarfs can also make for a point of light that fluctuates regularly in brightness. These impostors have led to some astronomical disappointments.
But NASA announced at the press conference that a new method of analysis, developed by Tim Morton, can weed out dud planets from the candidate list en masse, without needing case-by-case confirmation from ground-based telescopes. Morton’s method accomplishes this by running Kepler’s list of candidates through a statistical filter based on how common impostors are in our galaxy. Then the new method compares the star’s brightness and dimming to an ideal model of a star and planet with an “edge-on” orbit. This adds up to unprecedented accuracy in predicting whether a given star is really being eclipsed by a planet.
In keeping with their theme of “orange is the new blue,” NASA showed the new Kepler findings in orange in these images from the briefing, and older Kepler discoveries or observations from other telescopes are shown in shades of blue.
Kepler was conceived from the beginning as a mission for finding Earth-like planets elsewhere in the galaxy, and its original mission was a success, returning conclusive evidence for almost a thousand exoplanets within the Milky Way galaxy. But no plan survives contact with the enemy, and in this case, the enemy is the cold, hard vacuum of space. Kepler has been plagued by problems in its reaction wheels, leaving it with a mechanical Charley horse that prevents it from looking smoothly around in the sky. And apparently even NASA sometimes has to ask “Have you turned it off and back on again?” But Kepler just won’t quit. So the ground team decided, collectively, to do it live. They’re applying these new methods of analysis and confirmation to wring as much science as they can out of the telescope before its fuel runs out, sometime about two years hence.
When Kepler finally does run out of fuel, it’ll pass the baton to TESS and the James Webb Space Telescope, which will watch the skies in the visible and IR bands as we continue to seek new worlds elsewhere in space.