Scientists have announced the discovery of three
planets, in two planetary systems, that are in or on the edge of the so-called
habitable zone, the range that is just the right distance from their stars so
they wouldn't be too hot or too cold to have liquid water.
They made these discoveries with NASA's Kepler space
telescope.
Kepler-62
William Borucki, the Kepler science principal
investigator at NASA's Ames Research Center in California, described the
Kepler-62 planetary system, which he says is 1,200 light years away. One
light year is 10 trillion kilometers.
Much like our solar system, he said, Kepler-62 is
home to two habitable-zone worlds, called Kepler-62e and Kepler-62f.
Those planets are about one-and-a-half times the size of Earth.
"In fact, these two planets are our best
candidates for planets that might be habitable, not just in the habitable
zone," he told reporters at a news conference at Ames. "They're
part of a planetary system of five planets that we've discovered so far, but
these are the two that are most important."
Borucki said 62e might be a water world, but
scientists aren't certain as they only know its radius, not its mass. He
says planet 62f, the smaller of the two, might very well be a rocky planet, and
possibly have polar caps, significant land masses and
water.
Planets 62e and 62f orbit a star about two-thirds
the size of our sun and one-fifth as luminous. Borucki says if you
imagined yourself standing on 62f, it would be as bright as a cloudy day on
Earth.
Why Size
Matters
These are the smallest exoplanets found in a
habitable zone.
Lisa Kaltenegger of the Max Planck Institute for
Astronomy in Heidelberg, Germany, says scientific models indicate that planets
about this size could have water.
"The fascinating idea is that maybe we've
actually found the first ocean planets, the first water worlds out there, and
what it just shows you is the diversity that we're discovering out there,"
she said. "And let me say that we only have the radius, so what we
infer from the models is very exciting but always has to be taken a little bit
with a grain of salt."
Kepler-69
Thomas Barclay, a Kepler scientist at the Bay Area
Environmental Research Institute in California, is most excited about the
discovery of a planet in another system -- Kepler 69. He says Kepler-69c
is a planet 70-percent bigger than Earth that orbits a sun-like star, and it's
just on the edge of the habitable zone.
"The habitable zone is a region between fire
and ice. Well, this is orbiting closer to the fire than the ice," he
said. "We consider this perhaps to be more of a super-Venus than a
super-Earth, perhaps."
Kepler
Space Telescope
The Kepler space telescope explores the structure
and diversity of planetary systems. It finds planets by looking for tiny
dips in the brightness of a star that occur when a planet crosses in front of
it.
Kepler was launched in 2009, and it has found more
than 100 planets.
Sources :
http://www.voanews.com/content/kepler-space-telescope-spots-distant-planets/1644581.html
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