For the first time, astronomers have discovered seven Earth-size planets orbiting a nearby star — and these new worlds could hold life. NASA and the Belgian-led research team announced the news Wednesday. This cluster of planets is 40 light-years away in the constellation Aquarius. They circle tightly around a dim dwarf star called Trappist-1, barely the size of Jupiter. Three planets are in the so-called habitable zone, where 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 planets could support some type of life.
Last spring, the University of Liege’s Michael Gillon reported finding three planets around Trappist-1. Now the count is up to seven, and Gillon says there could be more.
How do the Orbits of the TRAPPIST-1 Star System's Planets Compare
to Our Own Solar System?
The dwarf star is roughly the size of Jupiter, and its system of seven known planets — called TRAPPIST-1b, 1c, 1d, 1e, 1f, 1g, and 1h — is relatively small compared to our own. In fact, one "year" on the innermost planet, 1b, lasts only about 1.5 Earth-days. The outermost planet, 1h (which scientists have caught only a fleeting glimpse of), may take about 20 Earth-days to orbit the star.
"If we put the TRAPPIST-1 star in the place of the sun, we'd have all seven planets inside the orbit of Mercury," Emmanuël Jehin, another co-author at the Université de Liège, said on the call. But that isn't a deal-breaker for the possibility of life. TRAPPIST-1's surface temperature is about half that of the sun's, making it "ultra-cool" as stars go. However, if a planet orbits closely enough, it can receive the same amount of solar energy as the Earth receives from the sun at 93 million miles away. All of TRAPPIST-1's worlds appear to be "temperate" and not close enough to get roasted.
The team said it's "very hard to know" if they just got lucky with their unprecedented discovery of seven Earth-size planets around a single star, or if such an abundance of worlds is common, said Amaury Triaud, fellow co-author and astronomer at the Institute of Astronomy in Cambridge, UK. Either way, the bounty of worlds may vastly improve the chances that humans aren't alone in the Milky Way galaxy, let alone the universe at large.