14 DAY TRIAL // An analysis of red stars in the Milky Way has revealed that Earth-like, rocky extrasolar planets are very common inside the habitable zones surrounding these objects. This also implies that there is a huge chance life can develop on at least some of these worlds.
Faint red stars have habitable zones that are located much closer to the stellar surface than the Sun's, for example. This means that the band where liquid water may exist is not roughly one astronomical unit (93 million miles or 157 million kilometers) away, but rather a lot closer.
Given the number of red stellar objects in the Milky Way, a new analysis from experts at the European Southern Observatory (ESO) suggests that as many as several tens of billions of rocky exoplanets may exist throughout our galaxy.
About one hundred of these worlds may be located in the Sun's immediate neighborhood, scientists add. This discovery paves the way for conducting a new series of investigations, this time aimed at finding Earth-like worlds exclusively.
For the new study, an international collaboration of astronomers used the High Accuracy Radial Velocity Planet Searcher (HAPRS) spectrograph instrument, on the ESO 3.6-meter telescope, at the La Silla Observatory, in the Chilean Andes.
A quick analysis of the night sky will reveal that as many as 80 percent of all stars in the Milky Way are type M dwarfs. This is primarily why the astronomers were so interested in studying those bodies.
“Our new observations with HARPS mean that about 40% of all red dwarf stars have a super-Earth orbiting in the habitable zone where liquid water can exist on the surface of the planet,” researcher Xavier Bonfils explains.
He is based at IPAG, Observatoire des Sciences de l'Univers de Grenoble, in France, and was also the leader of the international astronomical collaboration that led the investigation.
“Because red dwarfs are so common – there are about 160 billion of them in the Milky Way – this leads us to the astonishing result that there are tens of billions of these planets in our galaxy alone,” he adds.
The HARPS investigation spanned 6 years, and saw researchers monitor 102 red dwarf stars in the southern sky. Nine super-Earth-class exoplanets were discovered during this time, two of which are located in their parent star's habitable zones.
But there are also some factors that may prevent the development of life on these worlds, experts say.
“Red dwarfs are known to be subject to stellar eruptions or flares, which may bathe the planet in X-rays or ultraviolet radiation, and which may make life there less likely,” says team member Stéphane Udry, from the Geneva Observatory.