Two Earth-size planets orbiting a nearby star are now confirmed to be rocky, strengthening the case that they might be habitable, a new study finds.
The atmospheres of these worlds may range from vanishingly thin, like that of Mars, to hellishly dense, like Venus' air — and, possibly, comfortably in between, like Earth's, the researchers said.
In May, astronomers reported the discovery of three Earth-size planets orbiting a dim, cold, red star named TRAPPIST-1. This "ultracool dwarf" is located in the constellation Aquarius, about 39 light-years from Earth. (For comparison, Alpha Centauri, the nearest star system to our own, is about 4.3 light-years from Earth.) [10 Exoplanets That Could Host Alien Life]
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