NEW YORK — Another Earth could be circling the star right next door to us.
Astronomers announced Wednesday that they had detected a planet orbiting Proxima Centauri, the closest neighbor to our solar system.
Intriguingly, the planet is in the star’s “Goldilocks zone,” where it may not be too hot nor too cold. That means liquid water could exist at the surface, raising the possibility for life.
Although observations, particularly by NASA’s Kepler planet-finding mission, have uncovered a bounty of Earth-size worlds throughout the galaxy, this one holds particular promise because it might someday, decades from now, be possible to reach.
It’s 4.2 light-years, or 25 trillion miles, away from Earth, which is extremely close in cosmic terms.
One astronomer likened it to a flashing neon sign. “I’m the nearest star, and I have a potentially habitable planet!” said R. Paul Butler, an astronomer at the Carnegie Institution for Science and a member of the team that made the discovery.
Guillem Anglada-Escudé, an astronomer at Queen Mary University of London and the leader of the team that made the discovery reported in the journal Nature, said, “We know there are terrestrial planets around many stars, and we kind of expected the nearby stars would contain terrestrial planets. This is not exciting because of this. The excitement is because it is the nearest one.”
Beyond the planet’s size and distance from its parent star, much about it is mysterious. Scientists are working off computer models that offer mere hints of what’s possible: Conditions could be like those on Earth, but they could also be hellish like Venus, or cold and dry like Mars.
There is no picture of the planet, which has been designated Proxima b. Instead, Anglada-Escudé and his colleagues detected it indirectly, studying via telescope the light of the parent star. The astronomers found that Proxima b is at least 1.3 times the mass of the Earth, although it could be several times larger.
A privately funded team of scientists and technologists, led by the Russian entrepreneur Yuri Milner and the theoretical physicist Stephen Hawking, have announced Breakthrough Starshot Initiative, a project to launch a fleet of iPhone-size spacecraft within two to three decades.
Their proposed destination is the Alpha Centauri star system, which includes a pair of larger sunlike stars in addition to Proxima Centauri.
“We will definitely aim at Proxima,” said Avi Loeb, a Harvard astronomer who is chairman of an advisory committee for Breakthrough Starshot. “This is like finding prime real estate in our neighborhood.”
The newly discovered planet is much closer to its parent star, about 5 million miles apart. Because its star is a red dwarf, with less mass than the sun, Proxima b receives less warmth than Earth, but enough that water could flow on the surface.