It's amazing what a broken spacecraft can do. The Kepler Space Telescope has technically been busted for the past three years, but it keeps finding new exoplanets.
On Tuesday NASA scientists announced that Kepler has done it again, identifying 1,248 additional exoplanets, the largest single find of a clutch of exoplanets to date.
Launched in March 2009, Kepler is the first NASA mission to find potentially habitable Earth-size planets. For four years, Kepler monitored 150,000 stars in a single patch of sky, measuring the tiny, telltale dip in the brightness of a star and the way they seem to dim from the Earth's perspective. The variations in light can be used to figure out if there are any planets orbiting the stars and even to work out the size, mass and atmosphere of each orbiting planet. Scientists can then calculate if the planet in question is the right size to be rocky like the Earth and if the planet is far enough from the main star it orbits to have liquid water on its surface.
However, in 2013, just four years after its mission had started, Kepler broke. The spacecraft's reaction wheels, mechanisms used by spacecraft to control altitude, stopped working correctly and its original mission ended. But instead of giving up the whole craft as a lost cause, NASA scientists reworked the reaction wheels, creating a new mission called K2, which started in 2014.
And it's a good thing they opted to reconfigure the spacecraft because Kepler's K2 mission has paid off with huge numbers of confirmed exoplanets.
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All of the candidates from the most recent batch were spotted using Kepler in 2015. There were more than 4,000 potential planetary candidates spotted. From there, scientists sorted out the serious contenders, using statistical analysis to whittle down the field to include only contenders that had a 99 percent chance of actually being exoplanets.
Timothy Morton, associate research scholar at Princeton University in New Jersey and lead author of the scientific paper in The Astrophysical Journal on the analysis, used a statistical analysis method that could be applied to a whole bunch of potential planets at once, and then sorted them out using percentages. "Planet candidates can be thought of like bread crumbs,” Morton stated in a NASA release. “If you drop a few large crumbs on the floor, you can pick them up one by one. But if you spill a whole bag of tiny crumbs, you're going to need a broom. This statistical analysis is our broom."
In the newly validated batch of planets, nearly 550 could be rocky planets like Earth, based on their size, according to the release. Nine of these orbit in their sun's habitable zone, which is the distance from a star where orbiting planets can have surface temperatures that allow liquid water to pool. With the addition of these nine, 21 exoplanets now are known to be members of this exclusive group.
It's a good thing NASA scientists didn't assume that a broken telescope floating in outer space was automatically a useless telescope. Otherwise, we probably wouldn't be learning about all these new planets.