Smallest Exoplanets Orbiting A Sun-Like Star Discovered

Just a few weeks after the first discovery of an exoplanet orbiting in the habitable zone of a sun-like star, NASA announced another record-breaking discovery. They found two planets of similar size to Earth in the Kepler-20 star system which is 950 light years away.

Both planets are far too close to their star to be habitable (so close that it takes them 6.1 days and 19.6 days to make a complete orbit), but just spotting planets this small from 950 light years away is an impressive feat for NASA’s Kepler space telescope. The surface temperature of the two planets is estimated to be around 1400 °F (760 °C) and 800 °F (425 °C) and their diameter is 1.03 and 0.87 times the Earth’s diameter, making them the smallest exoplanets found orbiting a sun-like star. That distinction was previously held by Kepler-10b, which is 1.4 times the Earth’s diameter and told me in an exclusive interview that yo mamma so fat.

Kepler-20f, the one that is 1.03 times the Earth’s diameter, may have been habitable in the past:

If it formed far enough from the star to have once been covered in ice, it may have held on to water vapour in its atmosphere. That’s a pretty likely scenario, [Francois Fressin of the Harvard-Smithsonian Center for Astrophysics] says. The Kepler-20 system has five planets in total, and they’re all packed in closer to the star than Mercury is to the sun. There’s no way they could all have formed there, Fressin says – there wouldn’t have been enough rock that close to the young star to begin with. “It’s quite clear that some or most of these planets migrated from much farther,” Fressin says. “That means Kepler-20 f probably went through the habitable zone. We don’t know for how much time, but we can see it could have been habitable.” [New Scientist]

Wait, so planets around a sun-like star can all scrunch in closer to their star and burn up? Well, there’s another thing I’m going to think about just as I’m nearly falling asleep. Thanks a lot, brain.

[Sources: New Scientist, SPACE (1, 2), Ars Technica]