Avid followers of science news will remember seeing lots of recent articles about various exoplanets — that is, planets that orbit around a star besides our own sun. After the first discovery of an exoplanet just over 25 years ago, they've started rolling in fast and furiously, but still, everyone seems really excited about one exoplanet discovery in particular: Ross 128 b. The name doesn't make it sound like anything special and it's still far too soon to tell, but Ross 128 b might be the nearest planet that supports life.
"Until now we have awesome discoveries that found terrestrial planets orbiting Ross 128-like stars, e.g. [Proxima Centauri] or Trappist," says Nicola Astudillo-Defru, one of the exoplanet's co-discoverers, referring to recent exoplanet discoveries. "These two stars are quite active. The latter is not good when talking about habitability, hence, we are very happy to find that Ross 128 b orbits an inactive star, and that is so close!"
"The discovery is special because it confirms what astronomers have been finding for the past few years — that most stars in the night sky have their own worlds orbiting them and that a large fraction, about one in five, have an 'earth-like' planet," says Prof. Dr. Ben Moore, Director of the Center for Theoretical Astrophysics and Cosmology at the University of Zurich.
An "earth-like" planet, Prof. Dr. Moore explains, is "a world made of rock that is the right distance from the star to host liquid water." Those characteristics are what astro-biologists assume to be the basic requirements for life, which they've gathered from looking at our own solar system. Gas giants like Jupiter or baked, dead planets like Mercury that orbit too close to a powerful star don't provide the right circumstances for life to develop — but clearly, Earth does.
Another requirement for finding life at this stage is that the exoplanet in question must be close enough for astronomers to observe it — or, rather, observe the effect that it has on its star. Today's telescopes aren't powerful to actually see exoplanets because they're just not bright enough, so instead scientists use instruments that can detect minute "wobbles" of the host star, caused by the exoplanets' gravitational pull as they orbit the star. This is how a team using the High Accuracy Radial velocity Planet Searcher, or HARPS, found Ross 128 b — and they now believe that at only 11 light years away from us, it could be the closest planet that potentially hosts life.
Only last summer, another exoplanet discovery hit the news in a big way: the discovery of a planet around red dwarf star Proxima Centauri, which at just about 4.25 light years away from the Sun is our closest stellar neighbor. However, for all of the excitement that it caused, life on the planet that they named Proxima b is very unlikely.
Prof. Dr. Moore describes Proxima Centauri as "a very active star whose stellar wind is 2,000 times stronger than the solar wind." Stellar winds are streams of charged particles that a star emits, and if they're strong enough, they'll bathe nearby planets in radiation. "That is very dangerous for life and may mean that world is a dead world," Prof. Dr. Moore explains.
Ross 128, the star around which exoplanet Ross 128 b orbits, is also a red dwarf star — but it's not such an active one. "Ross 128b orbits a star that is much quieter [than Proxima Centauri], so this is the closest known exoplanet that may host life and that humans might want to visit one day," Prof. Dr. Moore writes. While the star is quite a bit dimmer than our Sun, Ross 128 b orbits closely enough that its average surface temperature could fall within the range where liquid water would exist.
Red dwarves, Dr. Astudillo-Defru explains, are not the ideal stars to host life, but given humanity's technological constraints now, they're not a bad place to look. "Today we do not have the technological capabilities to find an Earth-like planet orbing in the habitable zone of a Sun-like star," he tells Bustle. "The only example we have is the life on Earth, so it is more probable around Sun-like stars than around red dwarves."
Still, though, there's a whole lot of work to be done before anyone can be sure. about whether there actually is extraterrestrial life on Ross 128 b. Astronomers will need to study the planet's atmosphere in order to get any definite information, and they won't be able to do that until 2025 when the European Southern Observatory's Extremely Large Telescope, a much more powerful instrument than anything that we have now, begins working.
"ELT will search for biosignatures, molecules in the atmosphere of these worlds that would only be present because of life," Prof. Dr. Moore tells Bustle. "These may include oxygen or ozone from 'photosynthesizing life like on earth', or methyl chloride from fires (because only once living things can burn)."
The excitement, however, is not unwarranted; so many exoplanet discoveries immediately rule out the possibility of life, but Ross 128 b's hasn't — and in cosmic terms, it's right around the corner. While astro-biologists still can't be exactly sure what they're looking for, discoveries like Ross 128 b are quickly paving a way forward. "It is hard to predict what life may be like out there amongst the stars," says Prof. Dr. Moore. "The best strategy is to search everywhere and to expect the unexpected."