عادل احمد
مرحبا بك
عدد الرسائل : 69
تاريخ التسجيل : 05/11/2009
وســــــــــام النشــــــــــــــاط : 2
 | | Unraveling the mystery and potential of 'Super Earths' | |
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Exoplanet: n.
a planet that orbits a star outside the solar system. |
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Unraveling the mystery and potential of 'Super
Earths'
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Artist's visualization of a
small, terrestrial exoplanet.
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Terrestrial or Not?
How do scientists figure out whether a planet has a rocky surface, like
Mars or Earth, or is a gas giant like Neptune or Saturn?
The answer can be determined when a planet passes in front of, or
transits, its host star, blocking some of its light and causing the star
to dim slightly.
Artist's concept of a terrestrial exoplanet
transiting and the associated light curve.
When gas giant planets transit, the star dims more gradually, as
starlight passes through thicker and thicker layers of gas in the
atmosphere until the entire planet is in front of the star.
Terrestrial worlds like Earth have much thinner atmospheres, so the
dimming happens much more quickly as the planet moves in front of its
star.
Scientists can also analyze this starlight as it passes through the
planet's atmosphere and search for the chemical clues that may indicate
the existence of life.
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(PLANETQUEST) -- Not long ago, the only planets astronomers could find
orbiting other stars were massive, gaseous worlds that had more in
common with Jupiter than our own small, rocky planet.
As observation techniques have advanced, however, scientists have begun
discovering a newer, smaller type of planet - the tantalizingly named
"Super Earth."
"A 'Super Earth' is generally considered to be a planet that's up to
about 10 times the mass of the Earth," explains JPL scientist Steve
Edberg. "Planets bigger than that tend to be gaseous, like Uranus or
Neptune."
Super Earths are notable because, unlike gas giant planets, they're
small enough to have terrestrial surfaces or liquid oceans that could
support life as we know it.
And while none of the Super Earths discovered so far would be a good
place to take a vacation, scientists are hopeful that they'll find one
with the right chemical composition and at the right distance from its
star to support living things.
So what's life on a Super Earth like? First of all, cautions Edberg,
it's important to remember that a planet's mass and size are two
different things. "The relationship between a planet's size and its
mass isn't linear," Edberg explains. "A world that's 10 times the mass
of Earth will not be 10 times as big in diameter; it'll actually be
quite a bit smaller than that."
You might also feel a bit heavier than normal if you were to visit a
Super Earth, says Edberg, because "a bigger planet is going to have more
gravity...it's also probably going to have a thicker, more dense
atmosphere than Earth's."
Despite these differences, Edberg points out that under the right
conditions, a Super Earth could harbor living things. "You might not
get redwood trees and basketball players," he says, "but you'd still
have the right ingredients for life to get established."
And as the Super Earth discoveries begin to pile in, chances are that
the discovery of such an Earthlike planet may be just around the corner.
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