A group of scientists working out of the European Southern Observatory in Chile have discovered a new planetary neighbor, Ross 128 b. Only 11 light years away from Earth, Ross 128 b isn't the closest exoplanet, but it might be the most promising candidate for alien life.
With any newly discovered exoplanet scientists determine its viability for life based on the circumstellar habitable zone, other wise known as the "Goldilocks Zone." If a planet orbits its parent star too closely or too distantly it can't meet the conditions for life. For liquid water and atmosphere to exist the planet has to be in the orbital sweet spot, where that spot it depends on the star.
For Ross 128 b that sweet spot is about 4.5 million miles. It's a much closer habitable distance than the 93 million miles between Earth and our Sun because Ross' parent star is a red dwarf.
As far as stars go red dwarfs are unique. They are the smallest stars that burn hydrogen, but they have no core which allows them to burn for trillions of years. The smaller, cooler stars are fairly common, in fact their the most often observed by SETI simply because of the sheer number of them. Active red dwarfs however pose significant challenges to life though, the greatest threat being solar flares. This is the problem with Proxima Centauri, the closest star to our sun at 4.2 light years away. Though Proxima Centauri has an exoplanet within its habitable zone it's a very active star.
“Those flares can sterilize the atmosphere of the planet,” said Xavier Bonfils of the Institute of Planetology and Astrophysics in Grenoble, France, the lead author of a paper describing the planet. “Ross 128 is one of the quietest stars of the neighborhood.”
Astronomers found the planet using ESO's HARPS, the High Accuracy Radial velocity Planet Searcher. The planet itself isn't visible to the naked eye so scientists measure the wobbles and wavelengths emanating from the star which are caused by the gravitational pull of the planet.
Current scientific instrumentation is not sensitive enough to to observe these wavelengths from stars similar to our sun so the dimmer red dwarfs are ideal candidates for now. And the hope is that the next generation of large terrestrial telescopes will finally be able to directly observe the orbiting planets and possibly identify molecules in the atmosphere. “It would be rather easy to search for oxygen in the atmosphere of such a planet,” Dr. Bonfils said.
Since 1988 scientists have discovered 3,693 exoplanets. While some hold the potential to support life most can be disqualified for any number of inhabitable conditions. Though interstellar travel may be centuries off we should have a good idea of where to go by the time we're leaving Earth.