Most of the exoplanets discovered by Kepler, TESS, and other initiatives are much larger than Earth. Bigger planets are much easier to spot with our current technology, but scientists suspect there are a lot of Earth-like planets out there, too. Astronomers analyzing data from the Kepler mission have spotted one such planet that almost fell through the cracks, and it might be the most Earth-like planet ever discovered.
This exoplanet, dubbed Kepler-1649c, sits about 300 light-years away from Earth — that’s practically right next door in galactic terms. Kepler shut down in 2018 after running out of fuel to stabilize its orientation. That’s after the failure of multiple gyroscopes that necessitated a more limited survey of the sky several years before. Still, Kepler has managed to find thousands of potential exoplanets, and it’ll take years to analyze all its data.
Kepler used the transit method to look for exoplanets. It would watch large groups of stars, tracking dips in light that could indicate a planet passing in front of the distant stars. Most of the dips are from other astronomical phenomena, but about 12 percent come from exoplanets. NASA’s Ames Research Center developed a program called Robovetter to help sift through the mountain of data and identify that 12 percent. Initial computer analysis of the Kepler-1649 system didn’t flag the minute signal of Kepler-1649c, but a new review by humans caught it.
The newly discovered world is just 1.06 times the size of Earth — no other Kepler exoplanet is closer in size to Earth. Some other exoplanets like TRAPPIST-1f and Teegarden C are slightly closer (both 1.04 times Earth-size), but scientists discovered that world with the Spitzer Space Telescope. Unlike Earth, Kepler-1649c orbits a red dwarf, which is smaller and cooler than the sun. However, Kepler-1649c is close enough to the star (orbits once every 19.5 Earth days) that gets about 75 percent as much light as Earth. That could mean it has Earth-like temperatures and liquid water.
Scientists do not currently know anything about Kepler-1649c’s atmosphere, which would affect the surface temperature. Its mass is also unknown; it could be heavier or much lighter than Earth. Just being in the habitable zone and about the right size doesn’t mean Kepler-1649c is Earth-2. So, don’t go packing your bags just yet. Because this solar system is relatively nearby, it’s a prime target for future study with instruments like the upcoming James Webb Space Telescope. You know, if it ever launches.
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