Water Found On A Potentially Life-friendly Alien Planet

In a first for astronomers studying worlds beyond our solar system, data from the Hubble Space Telescope have revealed water vapor in the atmosphere of an Earth-size planet. Although this exoplanet orbits a star that is smaller than our sun, it falls within what’s known as the star’s habitable zone, the range of orbital distances where it would be warm enough for liquid water to exist on a planet’s surface. The discovery, announced this week in two independent studies, comes from years of observations of the exoplanet K2-18b, a super-Earth that’s about 111 light-years from our solar system. Discovered in 2015 by NASA’s Kepler spacecraft, K2-18b is very unlike our home world: It’s more than eight times the mass of Earth, which means it’s either an icy giant like Neptune or a rocky world with a thick, hydrogen-rich atmosphere.

K2-18b’s orbit also takes it seven times closer to its star than Earth gets to the sun. But because it circles a type of dim red star known as an M dwarf, that orbit places it in the star’s potentially life-friendly zone. Crude models predict that K2-18b’s effective temperature falls somewhere between -100 and 116 degrees Fahrenheit, and if it is about as reflective as Earth, its equilibrium temperature would be roughly the same as our home planet’s.

This is the only planet right now that we know outside the solar system that has the correct temperature to support water, it has an atmosphere, and it has water in it—making this planet the best candidate for habitability that we know right now,” University College London astronomer Angelos Tsiaras, a coauthor of one of the two studies, said during a press conference.

Source: https://www.nationalgeographic.com/