Astronomers just announced the discovery of yet another exoplanet, just one of thousands now, but this one is quite interesting and exciting for a variety of reasons. The planet, called Ross 128 b, is an Earth-sized world orbiting a star only 11 light-years away. Not only is it nearly the same size as Earth, the observations show that it is likely quite temperate, with temperatures similar to those on our planet as well. These findings make it possibly the best exoplanet candidate yet in the search for extraterrestrial life.
Ross 128 b was discovered by astronomers using the High Accuracy Radial velocity Planet Searcher (HARPS) at the La Silla Observatory in Chile, which is operated by the European Southern Observatory (ESO).
“This discovery is based on more than a decade of HARPS intensive monitoring together with state-of-the-art data reduction and analysis techniques. Only HARPS has demonstrated such a precision and it remains the best planet hunter of its kind, 15 years after it began operations,” said Nicola Astudillo-Defru from the Geneva Observatory – University of Geneva, Switzerland), who co-authored the discovery paper.
The planet orbits the red dwarf star Ross 128 every 9.9 days. Even though it orbits so close to the star, temperatures are calculated to be temperate, since the star is a lot smaller and cooler than our Sun. There is still some debate as to whether the planet is actually inside the "habitable zone" of the star, where liquid water could most likely exist on the surface, but what astronomers have learned so far makes them optimistic that the planet could be quite potentially habitable. Since Ross 128 b receives only 1.38 times more irradiation than the Earth, its equilibrium temperature is estimated to lie between -76°F and 68°F (-60°C and 20°C). Not bad.
Ross 128 b is now the second closest known Earth-sized temperate exoplanet. The one orbiting Proxima Centauri is closer, but that red dwarf star is more active than Ross 128, sending out frequent, intense flares which could adversely affect the habitability of any planets there. Ross 128 is much quieter.
Many exoplanets are now being discovered orbiting red dwarf stars, which are the most common stars in our galaxy. There are now estimated to be billions of planets in our galaxy alone.
Another interesting fact is that while Proxima Centauri is currently the closest star to us, apart from the Sun of course, Ross 128 is gradually moving closer and in about 79,000 years will become the closest star.
The discovery of Ross 128 b is raising some eyebrows for another reason as well - its star is the same one that was in the news this past spring and summer when SETI astronomers detected unusual radio signals coming from the direction of the star, first heard in May 2017. At the time, it was tentatively concluded that they were probably from an unknown satellite and not aliens, but this new discovery may prompt astronomers to take another look.
"So sadly, we've already looked closely at Ross 128 and have come up empty. Nonetheless, as Ross 128b is such an exciting target, we are considering additional, deeper observations at radio and optical wavelengths. 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."
Ross 128 b will also be a prime target for ESO's upcoming Extremely Large Telescope (ELT), which would be capable of detecting possible biomarkers in its atmosphere such as oxygen. Other closer exoplanets will also be able to be studied in this way in the next few years, by ELT and other telescopes, perhaps bringing us closer than ever before to finding the holy grail of exoplanetology - another inhabited world.
The new research paper is available here.