European astronomers say that just outside our solar system they've
found a planet that's the closest you can get to Earth in location and
size.
It is the type of planet they've been searching for across
the Milky Way galaxy and they found it circling a star right next door —
25 trillion miles (40 trillion kilometers) away. But the Earth-like
planet is so hot its surface may be like molten lava. Life cannot
survive the 2,200 degree heat of the planet, so close to its star that
it circles it every few days.
The astronomers who found it say
it's likely there are other planets circling the same star, a little
farther away where it may be cool enough for water and life. And those
planets might fit the not-too-hot, not-too-cold description sometimes
call the Goldilocks Zone.
That means that in the star system Alpha Centauri B, a just-right planet could be closer than astronomers had once imagined.
It's
so close that from some southern places on Earth, you can see Alpha
Centauri B in the night sky without a telescope. But it's still so far
that a trip there using current technology would take tens of thousands
of years.
But the wow factor of finding such a planet so close has
some astronomers already talking about how to speed up a 25
trillion-mile (40 trillion-kilometer) rocket trip there. Scientists have
already started pressuring NASA and the European Space Agency to come
up with missions to send something out that way to get a look at least.
The
research was released online Tuesday in the journal Nature. There has
been a European-U.S. competition to find the nearest and most Earthlike
exoplanets — planets outside our solar system. So far scientists have
found 842 of them, but think they number in the billions.
While
the newly discovered planet circles Alpha Centauri B, it's part of a
system of three stars: Alpha Centauri A, B and the slightly more distant
Proxima Centauri. Systems with two or more stars are more common than
single stars like our sun, astronomers say.
This planet has the
smallest mass — a measurement of weight that doesn't include gravity —
that has been found outside our solar system so far. With a mass of
about 1.1 times the size of Earth, it is strikingly similar in size.
Stephane
Udry of the Geneva Observatory, who heads the European planet-hunting
team, said this means "there's a very good prospect of detecting a
planet in the habitable zone that is very close to us."
And one of
the European team's main competitors, Geoff Marcy of the University of
California Berkeley, gushed even more about the scientific significance.
"This
is an historic discovery," he wrote in an email. "There could well be
an Earth-size planet in that Goldilocks sweet spot, not too cold and not
too hot, making Alpha Centauri a compelling target to search for
intelligent life."
Harvard planet-hunter David Charbonneau and others used the same word to describe the discovery: "Wow."
Charbonneau
said when it comes to looking for interesting exoplanets "the single
most important consideration is the distance from us to the star" and
this one is as close as you can get. He said astronomers usually impress
the public by talking about how far away things are, but this is not,
at least in cosmic terms.
Alpha Centauri was the first place the
private Search for Extra Terrestrial Intelligence program looked in its
decade-long hunt for radio signals that signify alien intelligent life.
Nothing was found, but that doesn't mean nothing is there, said SETI
Institute astronomer Seth Shostak.
The European team spent four
years using the European Southern Observatory in Chile to look for
planets at Alpha Centauri B and its sister stars Alpha Centauri A and
Proxima Centauri. They used a technique that finds other worlds by
looking for subtle changes in a star's speed as it races through the
galaxy.
Part of the problem is that the star is so close and so
bright — though not as bright as the sun — that it made it harder to
look for planets, said study lead author Xavier Dumusque of the Geneva
Observatory.
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