Published: Fri, November 17, 2017
Science | By Hubert Green

Close new Earth-size world, where year lasts under 10 days

Close new Earth-size world, where year lasts under 10 days

Astronomers working with ESO's High Accuracy Radial velocity Planet Searcher (HARPS) in Chile have discovered a temperate exoplanet orbiting the red giant star Ross 128. If any extraterrestrial species do exist in our stellar neighborhood, this might be our best chance yet at finding them.

For a red dwarf, Ross 128 is a relatively "quiet" star.

Red dwarfs have tightly bound "habitable zones" - the narrow temperature belts where surface water can exist as a liquid - but are also prone to deadly eruptions of ultraviolet radiation and X-rays. That's obviously great news if you fancy the idea aliens romping around on its surface, but at the moment we have no way of knowing if that's the case or not. It is named after the star that it orbits, Ross 128, which is only 11 light years away, making it one of the closest candidates for the search of extra-terrestrial life.

Study co-author, Dr Nicola Astudillo-Defru, of the University of Geneva in Switzerland, said: 'This discovery is based on more than a decade of HARPS intensive monitoring together with state-of-the-art data reduction and analysis techniques.

Habitable zone planets around most red dwarfs are likely to be severely irradiated, causing many scientists to doubt that life could survive on them.

Ross 128 b will by then take the crown from Proxima b and become the closest exoplanet to Earth, the reseachers said. "Nearby exoplanets are particularly exciting from a SETI perspective, as they permit us to search for and potentially detect much weaker signals than from more distant targets". The temperature of the star it orbits is only half the surface temperature of our Sun. Then, Ross 128 b will also replace Proxima Centauri's exoplanet, Proxima b, as our closest exoplanet and our closest potentially-habitable exoplanet. The exoplanet is predicted to have a temperature range of between -60 and 20C. Despite this proximity, Ross 128 b receives only 1.38 times more irradiation than the Earth. Red dwarves are the most common type of start in the galaxy and are often incredibly fierce, blowing away the planet's atmosphere - a necessity for the development of life.

One of the most interesting facts about Ross 128 b is that it is orbiting an inactive red dwarf star.

"New facilities at ESO will first play a critical role in building the census of Earth-mass planets amenable to characterisation". As a result, this "reflex motion" velocity is much easier to spot. If the planet reflects the optimal amount of light back into space, it may be conducive to the existence of liquid water.

[3] This is only possible for the very few exoplanets that are close enough to be angularly resolved from their stars.

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