Astronomers Find What May Be the Closest Exoplanet So Far 89
The Bad Astronomer writes: Astronomers have found a 5.4 Earth-mass planet orbiting the star Gliese 15A, a red dwarf in a binary system just 11.7 light years away (PDF). Other exoplanets candidates have been found that are closer, but they are as yet unconfirmed. This is more evidence that alien planets are common in the galaxy.
Re:OK Another one (Score:5, Informative)
5.4 earth masses puts it at about 1/3rd of a Neptune or a tiny fraction of a Jupiter or a Saturn.
It might even have a thin enough atmosphere to not completely crush a human.
Re:Time to travel 11 light years (Score:4, Informative)
Teah, they call that "thust to weight ratio" you're referring to specific impulse [wikipedia.org]
Re:OK Another one (Score:5, Informative)
But, of course, we don't know that the density of the planet is comparable to earth.
It is probably less. Of all the planets and spherical moons is our solar system, no other has a density as high as Earth. Earth's density is 5.5 gm/cc. The moon is 3.3. Mars is 3.9. If this planet has a density similar to the moon, its surface gravity would be about the same as Earth's.
Venus (Score:5, Informative)
If the surface gravity were about the same as the Earth's, wouldn't that mean that its atmospheric pressure at the surface would be about the same also. After all, it's gravity holding the gas down, and technically the atmospheric pressure is the weight of the gas above that point. Assuming the gas is trapped to the planet by the gravity, then you might have about the same amount of gas trapped above a point by a similar amount of gravity.
I'm just speculating though.
No. Atmospheric pressure is not simply a function of gravity. It is more a function of how much stuff there is in the atmosphere.
Consider that Venus' surface gravity is 0.904g wrt to Earth's (1g). And yet Venus's atmospheric pressure at the surface is 9.2 Megapascals whereas Earth's atmospheric pressure is 101.325 kilo-pascals (or 0.101325 Megapascals).
That is, even though Venus gravity is 90.4% that of Earth, its atmospheric pressure is 92 times that of Earth.