Cosmic Log
Where’s the nearest exoplanet with conditions that are right for life? Over the past couple of years, astrobiologists have talked up Proxima Centauri b, which is sitting just 4.2 light-years away.
But Villanova University astrophysicist Edward Guinan favors a world that’s just a bit farther out, at least in astronomical terms. It’s Barnard’s Star b, a super-Earth that orbits Barnard’s Star, 6 light-years from our solar system.
Red dwarf stars have been seen as the biggest potential frontier for alien life, in part because they’re the most common stars in our galaxy. But observations made using the Hubble Space Telescope suggest that the frontier might turn out to be a desert.
“We may have found the limit to habitable planets,” said Carol Grady, a co-investigator on the Hubble observations from Eureka Scientific in Oakland, Calif. She laid out the research team’s findings today at the American Astronomical Society’s winter meeting in Seattle.
The astronomical team that found the nearest exoplanet at Proxima Centauri has done it again with the reported detection of a super-Earth orbiting Barnard’s Star, the second-closest star system to our own.
The discoverers acknowledge, however, that they’re not completely sure yet.
“After a very careful analysis, we are 99 percent confident that the planet is there,” Spanish astronomer Ignasi Ribas, lead author of a study about the detection published today by the journal Nature, said in a news release. “However, we’ll continue to observe this fast-moving star to exclude possible, but improbable, natural variations of the stellar brightness which could masquerade as a planet.”
Assuming it exists, Barnard’s Star b would be at least 3.2 times as massive as Earth, tracing a 233-Earth-day orbit. It would be as close to its parent star as Mercury is to our own sun — but because Barnard’s Star is a dim red dwarf, surface conditions would be far too chilly for life as we know it. The surface temperature would be about 275 degrees below zero Fahrenheit (-170 degrees Celsius).
The SETI Institute is shifting the focus of its search for extraterrestrial intelligence to places that could harbor life that’s not as we know it: 20,000 red-dwarf star systems.
“Red dwarfs – the dim bulbs of the cosmos – have received scant attention by SETI scientists in the past,” SETI Institute engineer Jon Richard said today in a news release announcing the initiative. “That’s because researchers made the seemingly reasonable assumption that other intelligent species would be on planets orbiting stars similar to the sun.”
Red dwarfs are nothing like the sun: The brightest of the breed are a tenth as luminous as the sun, and some are just 0.01 percent as bright. But astronomers say they account for three-quarters of all stars.
The star that’s closest to our sun, Proxima Centauri, is a red dwarf. A variety of observing efforts, including the Pale Red Dot initiative, are looking for planets around Proxima Centauri.