A few months ago, astronomers discovered an incredible planetary system just 40 light-years away with three planets, TRAPPIST-1, one of which orbits in the star's habitable zone. Now a different team has confirmed the initial thoughts that the planets are roughly the same size as Earth.
Our instruments are not good enough yet to directly observe most exoplanets, so to estimate their properties we need to make sure we understand the host star well. TRAPPIST-1 has well-defined properties, but astronomers weren’t sure if it had a companion star, which would have changed the estimated sizes of the planets.
A team led by Steve Howell from NASA’s Ames Research Center used the Gemini South Observatory in Chile to establish if there’s more than one star in the system. In a paper, published in the Astrophysical Journal Letters, the researchers confirmed that the system doesn’t appear to have a small star or brown dwarf as a companion.
If the astronomers were estimating the properties of the system thinking they were seeing a single star when two were present, they could get the size of the exoplanets wrong by more than a factor of two. These observations therefore confirm that the three planets are indeed Earth-sized, as originally calculated.
"Knowing that a terrestrial-size potentially rocky planet orbits in the habitable zone of a star only 40 light-years from the Earth is an awesome finding," Howell said in a statement.
“The TRAPPIST-1 system will continue to be studied in great detail as these transiting exoplanets offer one of the best chances to characterize the atmosphere of an alien world."
The next round of observations for this fascinating system will start later this year, when the planet-hunting observatory Kepler will start a detailed monitoring campaign for about 75 days, as part of its K2 mission.
The precise measurement will allow for better estimates of the properties of the exoplanets, but it will also look for other potential planets orbiting the system. TRAPPIST-1 will definitely be a telescope target for many years to come.