Astronomers at NASA say they’ve found seven planets roughly the size of Earth that could have liquid water on their surfaces.
The finding, published Wednesday in the journal Nature, follows the team's discovery in May of three Earth-sized planets orbiting the dwarf star, called TRAPPIST-1. But UC San Diego physics professor Adam Burgasser, a co-author of the Nature paper, said what they thought was the furthest planet from the star was actually five separate planets.
The astronomers had been examining the star from a telescope in Chile to see if its brightness dipped regularly as the planets passed in front of it. They determined that the two closest planets completed an orbit about once every two days. Since the telescope wasn't always able to observe the star, they couldn't be sure about the third planet.
"You get a patchy shot at looking at these transit events," Burgasser said.
Burgasser and his colleagues were then able to use the Spitzer Space Telescope to observe TRAPPIST-1 continuously for 20 days, determining that there were seven Earth-sized planets in its orbit.
“That was enough to see that, in fact that last transit or that last detection was actually multiple planets sort of contributing and then that’s how we found the other five planets we hadn't seen before," Burgasser said.
Three are in what's called the star's "habitable zone," an area where they're neither too hot or too cold to have liquid water.
"All of these seven planets could have liquid water – key to life as we know it – under the right atmospheric conditions, but the chances are highest with the three in the habitable zone," NASA said in a press release.
That's a record number of possibly habitable planets found around a single star outside our solar system.
“The big excitement about any of this stuff is of course what we're really interested in ultimately which is, is there life beyond our Earth?" Burgasser said.
Burgasser joined KPBS Midday Edition on Wednesday with more on the discovery and how aspiring planet hunters can join the search for new worlds.
