Aussie team helps identify ‘super-Earth’ and ‘sub-Neptunes’

NASA’s Goddard Space Flight Center/Scott Wiessinger

Just 73 light-years from Earth — just a hop, skip, and a jump in galactic terms — a star called TOI-270 is orbited by a “super-Earth” and two “sub-Neptunes,” among possibly other planets. NASA’s Transiting Exoplanet Survey Satellite (TESS) discovered the planets, which are among the closest to Earth so far observed. Scientists from Australian National University helped make the identification of a rocky planet about one and a quarter times the size of Earth and two gaseous planets about half the size of Neptune with hydrogen atmospheres.

TESS, which launched last year, is scouring space for possible planets. ANU associate professor Michael Ireland told the Sydney Morning Herald that there is a better than 50 per cent chance that a fourth planet in TIO-270’s solar system is Earth-like and in the star’s habitable zone. The three planets identified so far are outside the “Goldilocks zone,” meaning they are either too close to the star and thus too hot, or too far and thus cold, to support life. One of the sub-Neptunes could have moons capable of supporting life, though they have not yet been detected. Scientists published their findings in the journal Nature Astronomy

“It’s about understanding our place in the universe; is our solar system unique or are there other planets like Earth out there?” Ireland told the Herald. “If the answer is our planet is extremely rare and there are few like it in the galaxy, then I think you’d feel a bit differently about space exploration and the future of humanity, than if there were (Earth-like) planets next door.”

Finding worlds nearby that could support life leads dreamers to wonder if we could someday colonise them should Earth become uninhabitable. When TESS ends its mission in 2020, the car-sized satellite will have surveyed 85 per cent of the sky.