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| © ESO/M. Kornmesser This image shows an artist's impression of the planet's surface. Credit: ESO/M. Kornmesser |
By Ashley Strickland, CNN
Astronomers believe that recently discovered super-Earth
Barnard's star b, only six light-years away, might be able to support
life.
Barnard's star b was only announced in November; it orbits Barnard's
star, the closest solitary star to our sun. This makes it the second
closest-known exoplanet to us. Previously, an exoplanet was found
orbiting in the three-star Proxima Centauri system, only 4.2 light-years away.
Though
Barnard's star b is more than three times the mass of Earth, it's also
frozen, which didn't sound very encouraging for supporting life.
The
planet is probably dimly lit by its star and slightly colder than
Saturn. The researchers believe that it is an icy desert with no liquid
water, a hostile environment where the average surface temperature is
around minus-274 degrees Fahrenheit.
But Villanova University
astrophysicists Edward Guinan and Scott Engle announced Thursday that
they believe life could function in an unusual way on the frozen planet.
The announcement was made during the 233rd meeting of the American
Astronomical Society in Seattle.
Beneath its frozen surface,
Barnard's star b could have a hot, liquid core of iron and nickel, which
could support primitive life with geothermal activity.
"Geothermal
heating could support 'life zones' under its surface, akin to
subsurface lakes found in Antarctica," Guinan said. "We note that the
surface temperature on Jupiter's icy moon Europa is similar to Barnard
b, but because of tidal heating, Europa probably has liquid oceans under
its icy surface."
Guinan also believes that future telescopes
could take a closer look at Barnard's star b. This would make it one of
the only Earth-size exoplanets nearby that could be imaged.
"Such observations will shed light on the nature of the planet's atmosphere, surface and potential habitability," he added.
Finding a frozen Super-Earth
The
exoplanet was found after stitching together 20 years of data,
including 771 individual measurements, from seven instruments. For
years, astronomers thought they would find a planet around the nearby
star, but it eluded them.
"The biggest 'kick' about this
discovery is the host star," Paul Butler, co-author of the November
study in which the planet was announced and astronomer at the Carnegie
Institution for Science, wrote in an email. "Barnard's star is the
'great white whale' of planet hunting."
And to look at it through a
telescope, the star appears to be moving the fastest among the other
stars in the night sky. This is because it's moving quickly in relation
to the sun, and it's the nearest single star in the sky to us, Butler
said.
"The star is named in honor of the great American
astronomer Edward Emerson Barnard, who was a pioneer of stellar
photography and astrometry," Butler said. "He recognized that this star
had the largest known proper motion a century ago."
The planet is
about the same orbital distance from its star as Mercury is from our
sun, making a full pass around the star every 233 days. This places it
in the "snow line" of the star, where it's cold enough for water to
freeze into solid ice. This region in a planetary system is where the
building blocks of planets are thought to form, collecting material to
become cores. As they migrate closer to their host stars, gathering more
material, they become planets.
The red dwarf star itself emits
only about 0.4% of our sun's radiance, so the planet receives about 2%
of the intensity that Earth receives from its sun. This is because
Barnard's star is in the class of M dwarf stars, cooler and less massive
than our sun. It's also an old star that predates our own solar system.
"Barnard's
Star is about twice as old as the Sun -- about 9 billion years old
compared to 4.6 billion years for the Sun," Villanova's Engle said. "The
universe has been producing Earth-size planets far longer than we, or
even the Sun itself, have existed."
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