At the end of last year, astronomers announced that they had found a super-Earth around the star of Barnard – one of the suns closest to ours. The discovery of a planet just six light-years away was enough to excite both astronomers and the public. However, researchers who found the planet said they suspected that the icy world would not support life.
But now a group of astronomers are saying that such pessimism may be premature. On Earth, geothermal sources produce heat and create unique environments where life thrives in places that would otherwise be hard to earn a living – like the icy, dark depths of the oceans. The team says similar lawsuits may be in action in this world, which is officially cataloged as Barnard b.
Barnard's star is a low mass dwarf red, which means it is small, ancient and only emits a fraction of the energy that our sun expels. The planet itself is about three times the mass of the Earth and orbits the star every 233 days. Then, because of its distant orbit around a small star, the planet should be a very cold 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 rekindled the habitability potential of the planet. They said that if the world also has a large iron / nickel core and sufficient geothermal activity, features such as plumes and volcanic openings could create "living areas" of liquid water under the frozen surface of the world.
In the zone
These living areas, according to study co-author Edward Guinan of Villanova University, may be "similar to the subterranean lakes found in Antarctica" here on Earth. The closest analogue, he said, is Lake Vostok, which lies well below the Antarctic ice, but does not freeze because it is heated by volcanism. Scientists have recently discovered evidence of life there. Guinan also compared these areas to regions close to potential hydrothermal vents in Europe, which most likely harbor a completely liquid ocean under a icy bark.
Europe, however, is warmed by the attraction of Jupiter's heavy gravity as well as the gravity of its neighboring moons. In Barnard b, the heat would come from the planet itself. Although the team estimates that Barnard's star age – and his planet – is twice as large as our own solar and solar systems, if the planet houses a large hot iron core, its larger mass can also improve and last for long geothermal. However, Guinan pointed out during the conference that "there is not much known about the super-Earth. Our models are everywhere. "
A liquid iron core, teamwork states, could offer protection against the deadly activity of the sun, since M-stars are known to bathe their surroundings with radiation that can ward off the atmospheres of their planets, particularly at the beginning of their lives.
The team targeted Barnard's star as part of the Villanova Living with Red Dwarf program, which has been underway for the past 20 years. "We were waiting for a planet to be discovered around Barnard's star," Guinan said. The researchers determined the age of the star and the planet using data dating back to 2003. Based on measurements of the star's brightness over time, they determined that it rotates approximately once every 142 days. From there, they calculated their age – about 8.6 billion years, or about twice the age of the Sun – using a relationship called period-age-activity relationship for red dwarfs, which links the rate of rotation and levels of activity of a star at his age.
The team also calculated the amount of X-rays and ultraviolet radiation that the star's planet would receive at a distance of 0.4 astronomical units (1 astronomical unit, or AU, equals the Earth-Sun distance) to determine the effects in any atmosphere Barnard b can host. They note that this effect is greater when the star is young and more active, and decreases as the star ages. When an M-dwarf, like Barnard's star, is young, they say that it spins faster and exposes ultraviolet and X-ray light that is tens to hundreds of times stronger, respectively, than when it is older . These high levels of radiation would probably damage or destroy the atmosphere on any surrounding planet. On the other hand, young Barnard's star would also have been brighter, heating his planet, which was closer in the past, enough for an atmosphere composed of greenhouse gases – though limited in life – to perhaps maintain a surface temperature which could withstand liquid water, if only briefly.
Today, Barnard b receives only about 2 percent of the Earth's radiation from the Sun, and is a cold world with a surface temperature of about -270 degrees Fahrenheit (-170 degrees Celsius). If you have water today, it will be frozen on the surface, with only the depths of the ocean potentially habitable in limited areas warmed by openings.
However, there is another possibility: Barnard B may be more massive than is currently believed. If its mass were actually larger, more than seven land masses, it would be gravity enough to maintain a thick atmosphere of hydrogen and helium, making it not a terrestrial super terrestrial, but an ice giant, the mini-Neptune. An ice giant, Guinan said at a news conference, would "prevent life" unless the planet has a tidal-warming Europe-type moon, which is where life can be found in the system, in that case.
However, Barnard continues to be an excellent candidate for cutting edge imaging techniques and the next generation of developing instruments.
"It is at the limit of being imaginable," said Guinan, and "beyond the edge of what can be imagined today."
Although more information is needed to determine Barnard's mass and potential for habitability, future work can open the door to a better understanding of super-Earths and what their environments and inhabitants might be like.