Astronomers discover potentially habitable planet 31 light years from Earth
- GJ 357 d is one of two previously unseen planets discovered around a star spotted by Nasa’s Transiting Exoplanet Survey Satellite
- At 6.1 times Earth’s mass, it could be the closest transiting planet in the solar neighbourhood that is friendly to life
A super-scorched planet orbiting around a nearby dim star has helped reveal the presence of two previously unseen planets – one of which could host liquid water and thus be friendly to life, astronomers say.
The blistering planet GJ 357 b, picked out by Nasa’s Transiting Exoplanet Survey Satellite (Tess), lies about 31 light years away in the constellation Hydra. It is only 22 per cent larger than Earth and circles its star every 3.9 days – tracing an orbit that is 11 times closer to its star than Mercury’s is to our sun.
This means that even though its M-dwarf star is roughly 40 per cent cooler than our sun, the planet is in all likelihood searingly hot – probably 254 degrees Celsius (490 degrees Fahrenheit) or so – even without the insulating effects of an atmosphere.
That uninhabitable world was the only one around this star spotted by Tess, which scans the skies looking for dips in a star’s light that might indicate that a planet is passing, or transiting, in front of it.
Astronomers used information from the ground-based telescopes to confirm GJ 357 b’s existence. In the process, they noticed clues that an additional pair of planets was also circling the same star.
These two planets, GJ 357 c and d, were found using the radial velocity method: by looking at the slight wobble in the star’s motions caused by its planets’ tiny gravitational tugs.