美國太空署的科學家們辛苦工作多年,終於在太陽系外發現一顆與地球極為相似的行星. 目前命名為 Kepler-186f.
所有科學內容可見於下列原文。
Scientists who have been hunting for
another Earth beyond our solar system have come across a planet that's
remarkably similar to our world.
It's almost the same size as Earth, and
it orbits in its star's "Goldilocks zone" — where temperatures are
not too hot, not too cold, and maybe just right for life.
But a lot about this planet is going to
remain a mystery, because it's 500 light-years away.
Researchers detected the planet while
poring over data collected by . The telescope spent years staring at 150,000
stars, watching for telltale dips in brightness that might mean a planet was
circling around a star.
One small star in the direction of the
constellation Cygnus showed signs of five planets. Four of them are tucked in
close to the star, so they're probably too hot for life.
But the fifth planet looked special.
"This planet orbits its star every
130 days," says of the SETI Institute and NASA's Ames Research Center.
It's called Kepler-186f, and it's just 10 percent bigger than Earth.
At least in our solar system,
Earth-sized planets are made of rock and iron and gas, says Quintana, "so
we can guess that Kepler-186f, being so close in size to Earth, has a high
probability of being rocky also and composed of those sorts of materials."
Conditions on the surface would depend
on what kind of atmosphere it had, if any. If it was like Earth, temperatures
wouldn't be balmy, Quintana says.
"Being on this planet would
probably be like being in San Francisco on a cool day," she says. "It
would be a much colder place to live."
It would be warm enough, however, for
one thing that's thought to be essential for life. "If this planet had the
right atmospheric conditions, and if there were water on the surface, it would
be likely in liquid form," says Quintana.
But if it has oceans, they would look
different.
"It's not going to have a deep
rich blue ocean, such as we have, because there's less blue light coming from
the star," says of NASA's Ames Research Center, another member of the team
that . "So the ocean would probably be a duller, grayer blue."
And because this planet orbits a dim,
red dwarf star, he notes that midday on this planet wouldn't be bright — it
would look more like an hour before sunset on Earth.
"It's very romantic to imagine
there'd be places out there that look like Earth, and that's what we're trying
to find — places that remind us of Earth," Barclay says.
Although Kepler-186f shares
characteristics with Earth, "it's not an Earth twin," he notes.
"It isn't around the same type of star. It's perhaps more of an Earth
cousin."
Still, it's the first time anyone has
found an Earth-size planet in the habitable zone of a distant star, Barclay
adds. "This is a really profound discovery. It's a major milestone."
Other experts on planets beyond our
solar system agree that this discovery is a big deal.
"This planet really is the same
size as the Earth and the same temperature," says of Harvard University.
"Up until this point, planets satisfied one of those two, but we really
didn't have one that was both those things together."
Both those things are key to life on
Earth, Charbonneau says, but we'll probably never know if this new planet has
life. "And the reason," he explains, "is that this star system
is just too far away from us."
Even though this planet is too distant
for follow-up work with other telescopes, it suggests similar worlds might be
out there orbiting other red dwarf stars, which are very common.
If scientists could find another planet
like this around a nearby star, he says, "we could really study the
atmosphere and really figure out something about whether it truly is Earth-like
and maybe whether it actually has life on the surface."
That's
why Charbonneau and other scientists will keep searching for other Earth-like
planets closer to home.我的感想是,她離地球是500光年,如果地球發生問題,我們能移民的最近目的地就是她。算算距離吧,目前還沒有光速火箭(如果有需要飛500年),所以飛機應是比較實際的交通工具。目前的時速多為每小時1000公里左右。我算了一下,這速度要飛五億年,飛機上要裝太多的水和其他食物。