Posted on 06/13/2005 12:42:00 PM PDT by The_Victor
WASHINGTON — A planet that may be Earth-like — but too hot for life as we know it — has been discovered orbiting a nearby star.
The discovery of the planet, with an estimated radius about twice that of Earth, was announced today at the National Science Foundation.
"This is the smallest extrasolar planet yet detected and the first of a new class of rocky terrestrial planets," Paul Butler of the Carnegie Institution in Washington said in a statement. "It's like Earth's bigger cousin."
Geoffrey Marcy, professor of astronomy at the University of California, Berkeley, added: "Over 2,000 years ago, the Greek philosophers Aristotle and Epicurus argued about whether there were other Earth-like planets. Now, for the first time, we have evidence for a rocky planet around a normal star."
Though the researchers have no direct proof that the new planet is rocky, its mass means it is not a giant gas planet like Jupiter, they said. They estimated the planet's mass as 5.9 to 7.5 times that of Earth.
It is orbiting a star called Gliese 876, 15 light years from Earth, with an orbit time of just 1.94 Earth days. They estimated the surface temperature on the new planet at between 400 degrees and 750 degrees Fahrenheit.
Gliese 876 is a small, red star with about one-third the mass of the sun. The researchers said this is the smallest star around which planets have been discovered. In addition to the newly found planet the star has two large gas planets around it.
Butler said the researchers think that the most probable composition of the planet is similar to inner planets of this solar system — a nickel/iron rock.
Gregory Laughlin of the Lick Observatory at the University of California, Santa Cruz, said a planet of this mass could have enough gravity to hold onto an atmosphere. "It would still be considered a rocky planet, probably with an iron core and a silicon mantle. It could even have a dense steamy water layer."
Three other extrasolar planets believed to be of rocky composition have been reported, but they orbit a pulsar — the flashing corpse of an exploded star — rather than a normal type of star.
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On the Net:
National Science Foundation: http://www.nsf.gov
Relatively speaking, I guess.
This is a significant factor in the orbital period:
Gliese 876 is a small, red star with about one-third the mass of the sun.
Sheila Jackson-Lee (D-Mars) will be green with envy (greener).
I'm curious if the gravity of a planet is affected by it's density. I know our gas giants aren't very dense yet they have extremely strong gravitational fields. Or is mass more of a factor than density?
Hope not, that whole death penalty thing and all. We could be executed for just responding to this thread!
No, probably Gliese 876 I, unless there's another planet closer in to it's sun.
Posting from Sol III.
Hot as Vulcan!
Gravitational pull is purely a function of mass and distance.
It's a terrestrial planet, but it sure ain't earthlike.
Gravity's affected by the planet's mass. Density is the mass per unit of volume, so they are related. Remember, Saturn has a density of less than 1 (the density of water) while Earth's density is 5 and some change. However, Saturn has a higher "surface" gravity than Earth because it is so much bigger.
So a rocky planet the size of Jupiter would have the same gravitational pull as a gas giant like Jupiter?
No. A rocky world that size (an impossibility) would be more massive than a gas giant and have a higher surface gravity.
From the only good line in Riddick...."If I owned this place and Hell...I'd live in hell, and rent this place out."
No. A rocky planet would have much greater mass that a gas planet of the same size.
The gravity field is dependent only on the mass. However the surface gravity is dependent on both the mass and the radius of the planet. The less dense planet will have a larger radius, by the cube root of the density ratio. It's surface gravity will be lower by the square of the cube root of the density ratio.
By their standards it's almost a carbon copy. If it's solid, has an atmosphere and isn't hot enough to melt most metals it's pretty close. I blame bad reporting for the impressing they convey, because to a layman "earth like" means survivable without a spacesuit and the closest thing we have to that is Mars.
Gravity is directly proportional to mass. Density has nothing to do with the equation. Gas giants have high gravity because even though they aren't dense, there's a lot of mass involved.
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