"This one's exciting."
A recently discovered exoplanet only 25 light years away resembles our own planet a lot more than once thought.
The distant world, dubbed GJ 3378b, orbits inside the
habitable zone of a red dwarf star — a type of star that is much smaller and
cooler than our Sun — where temperatures are just right for liquid water to
form on the surface.
But initially, its case for potentially supporting life
beyond that looked grim. Astronomers suspected it was a rocky world, but its
mass was at least five times more than Earth — or what astronomers called a
“super-Earth.” Along with its incredible surface gravity, such a heavy world
would possess a crushing atmosphere that would smother any chance of hosting
life.
That no longer appears to be the case, however. In a new
study published in The Astrophysical Journal, researchers from the University
of California, Irvine, took a second look at the exoplanet, finding that it’s a
much more manageable twice the mass of Earth. Combined with its proximity to
our solar system, it’s one of the most tantalizing nearby candidates for
potentially supporting life yet.
“This one’s exciting,” lead author Paul Robertson, a UC
Irvine associate professor of astronomy, said in a statement about the work.
“It’s one of our closest cosmic neighbors. 25 light-years sounds like a long
way, but the Milky Way is about 100,000 light-years across, so in that respect
it’s our next-door neighbor.”
There’s more detective work that needs to be done before we
know how hospitable to life GJ 3378b is. The biggest question mark is its
atmosphere. Does it have one, and is it robust enough to protect against the
radiation of its star? And how much pressure does it exert?
It’s a delicate balance. “If you scale the Earth down to the
size of an apple,” Robertson explained, “its atmosphere would be about as thick
as the skin of the apple.” This is just the right amount to support liquid
water and have breathable air, while still providing protection against space
radiation, he added.
There’s also a raging debate in astronomy over whether red
dwarf systems are habitable at all. These stars are believed to be highly
volatile, regularly unleashing powerful solar flares. Because their habitable
zones are smaller, that puts a potential life-supporting realm much closer to
these outbursts, which could strip them of their atmosphere and sterilize any
burgeoning life. Being so close to the star also means that any such planets
are likely to be tidally locked, in which the star’s gravity prevents them from
rotating so that one side is facing the star at all times.