Some astronomers have recently announced that they have found a super-Earth around Barnard’s star – one of the closest suns to our own. The discovery of a planet just six light-years away is enough to excite astronomers and the public alike. However, the researchers who found the planet said that they suspected the icy world couldn’t support life.
But now, a group of astronomers are saying such pessimism may be premature. On Earth, geothermal vents produce heat and create unique environments where life thrives in places otherwise difficult to eke out a living – like the frigid, dark deep of the oceans. The team says similar processes could be at work on this world, which is officially catalogued as Barnard b.
Barnard’s star is a low-mass red dwarf, which means it’s small, ancient, and only emits a fraction of the energy our sun puts out. The planet itself is about three times the mass of Earth and orbits the star every 233 days. So, because of its distant orbit around a tiny star, the planet should be a pretty frigid place where water would freeze on the surface.
But what about the water below the surface? On Thursday morning at the 233rd Meeting of the American Astronomical Society in Seattle, Washington, a team of astronomers rekindling the planet’s potential for habitability. They said that if the world also has a large iron/nickel core and enough geothermal activity, features such as volcanic plumes and vents could create “life zones” of liquid water under the world’s frozen surface.
These life zones, according to study co-author Edward Guinan of Villanova University, may be “akin to subsurface lakes found in Antarctica” here on Earth. The closest analog, he said, is Lake Vostok, which sits far below the ice in Antarctica, yet doesn’t freeze over because it’s heated by volcanism. Scientists recently found evidence of life there. Guinan also compared these zones to regions near potential hydrothermal vents on Europa, which very likely holds a completely liquid ocean underneath an icy shell.
Europa, however, is heated by the pull of Jupiter’s hulking gravity, as well as gravity from its neighbouring moons. On Barnard b, the heat would come from the planet itself. Though the team estimates the age of Barnard’s star – and its planet – to be about twice that of our own sun and solar system.
Currently, Barnard b only receives about 2 percent the radiation Earth receives from the Sun, and is a cold world with a surface temperature of nearly -275 degrees Fahrenheit (-170 degrees Celsius). If it does have any water left today, it would be frozen on the surface, with only the ocean depths potentially habitable in limited zones warmed by vents.
However, there is another possibility: Barnard b could actually be more massive than currently believed. If its mass is truly greater, more than seven Earth masses, it would have enough gravity to hold onto a thick atmosphere of hydrogen and helium, making it not a terrestrial super-Earth, but an ice giant, mini-Neptune instead. Nonetheless, Barnard b remains an excellent candidate for up-and-coming bleeding-edge imaging techniques and the next generation of instruments in development.
Although more information is needed to determine Barnard b’s mass and potential for habitability, future work may open the door to better understand super-Earths and what their environments and inhabitants could be like.