An artist's concept of what the TRAPPIST-1 planetary system may look like shows seven planets orbiting an ultra-cool dwarf star 40 light-years from Earth. The planets are all roughly the same size as the Earth and may support life. (Nasa /EPA)

For the first time, astronomers have discovered seven Earth-size planets orbiting a nearby star — and these new worlds could hold life.

This cluster of planets is less than 40 light-years away in the constellation Aquarius, according to NASA and Belgian researchers who announced the discovery Wednesday.

The planets circle tightly around a dim dwarf star called TRAPPIST-1. Three are in the “habitable zone,” where liquid water and, possibly life, might exist. The others are right on the doorstep.

Scientists said they need to study the atmospheres before determining whether these rocky, terrestrial planets could support some sort of life. But it already shows how many Earth-size planets could be out there.


An artist’s drawing shaws what the surface of the exoplanet TRAPPIST-1f may look like, based on available data about its diameter, mass and distances from the host star. (AP)

“There are 200 billion stars in our galaxy,” said co-author Emmanuel Jehin of the University of Liege, in Belgium. “So do an account. You multiply this by 10, and you have the number of Earth-size planets in the galaxy — which is a lot.”

Last spring, the University of Liege’s Michael Gillon and his team reported finding three planets around TRAPPIST-1. Now the count is up to seven, and Gillon said there could be more. Their latest findings appear in the journal Nature.

While faint, the TRAPPIST-1 star is close by cosmic standards, allowing astronomers to study the atmospheres of its seven temperate planets with ground and space telescopes. All seven look to be solid like Earth — mostly rocky and possibly icy, too.

They all appear to be tidally locked, which means the same side continually faces the star, just like the same side of our moon always faces us. Life could still exist at these places, the researchers explained.

“Here, if life managed to thrive and release gases similar to that that we have on Earth, then we will know,” Triaud said.

Chemical analyses should indicate life with perhaps 99 percent confidence, Gillon noted. But he added: “We will never be completely sure” without going there.

— Associated Press