Final Kepler Report Includes 219 New Potential Exoplanets
by Ryan Whitwam
Earth is the only planet we know of right now that supports life, but considering the scale of the universe it seems like there could be others. The first step in finding these Earth-like worlds is to detect planets orbiting nearby stars. That’s what NASA’s Kepler space telescope has been doing these past eight years. The project has had its ups and downs, but the final planetary catalog unveiled by astronomers during a recent meeting at the Ames Research Center signifies the final chapter of Kepler. Its grand total: 4,034 objects.
These exoplanets were detected by Kepler using what’s known as the transit method. The telescope watches a patch of the sky, recording dips in luminance that could indicate a planet passing between its host star and us. By monitoring over time, astronomers can determine the size, mass, and orbit of such a planet. This requires the distant solar system to be at just the right angle, and Kepler can only see a small segment of the sky. Still, we knew of only 300 probably exoplanets when Kepler launched. Now, there are thousands.
However, the Kepler satellite hit a snag four years ago when two of its four reaction wheels failed, leaving it unable to maintain orientation. The mission seemed doomed, but NASA worked out a clever solution in 2013 using the solar wind to stabilize the spacecraft in certain parts of its orbit. This K2 search program has been underway ever since, and it slated to come to an end on September 30th.
The list includes many objects that are confirmed planets, but everything on the list is at least 90 percent certain to be an exoplanet. To date, more than 1,200 exoplanets have been confirmed using Kepler data. The latest update to Kepler’s survey of the sky includes 219 new planetary candidates. Ten of them are in the habitable zone of their stars, meaning they (or their moons) could support life.
One analysis presented alongside the new data sheds light on the way smaller planets form. The most common “small” planets come in two sizes. There are rocky worlds about 1.5-times the diameter of Earth, known as super-Earths. Then, the commonality of planets drops off until you get to “mini-Neptunes” at about two times Earth’s diameter. All planets seem to begin with roughly the same amount of solid material in the core, then gas adheres in large quantities to create a gas giant. Alternatively, a small envelope of gas sticks and you get a planet like Earth.
The data acquired by Kepler will instrumental in the search for life. NASA plans to deploy a satellite in the 2030s that could capture images of these planets. In the meantime, the Webb Space Telescope might be able to image some of these planets with its 6.5-meter mirror. It launches in October 2018.
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Originally published at www.extremetech.com on June 20, 2017.