Super-Earth Discovered In Star's Habitable Zone

astroengine writes "The family of planets circling a relatively close dwarf star has grown to six, including a potential rocky world at least seven times more massive than Earth that is properly located for liquid water to exist on its surface, a condition believed to be necessary for life. Scientists added three new planets to three discovered in 2008 orbiting an orange star called HD 40307, which is roughly three-quarters as massive as the sun and located about 42 light-years away in the constellation Pictor. Of particular interest is the outermost planet, which is believed to fly around its parent star over 320 days, a distance that places it within HD 40307's so-called "habitable zone.""

Comments

Re:Fermi's p

[feedayeen]

seven times more massive than Earth...

so much for their early space program

Assuming 2 planets have equal densities, Mass increases proportional to R^3, but gravity is proportional to the inverse squared of the distance.... As a result, surface gravity increases only linearly with the radius.... in this case, the planet would have 1.9 times the radius of the Earth if it's the same density.

Earth has a very high density actually at 5.5g/cm3, it's actually the densest planetary object in our solar system. Most terrestrial objects are closer to 2 and the larger ones tend to be 3. It is entirely possible that it'll have a comparable surface gravity.

Re:Fermi's p

[Bill Currie]

No, his math is quite correct: M=d*4*pi*r^3, so M(p)/M(e) = (d*4*pi*r(p)^3)/(d*4*pi*r(e)) which simplifies to r(p)^3/r(e)^3, or (r(p)/r(e))^3, thus the ratio is the cube-root of 7: 1.913 (or 7.1: 1.922). Still, 2G would be a cow for us.

Re:Fermi's p

[dkf]

Solids and liquids are not significantly compressible.

While you're correct that they're a lot less compressible than a gas, you most certainly can still compress solids and liquids if you press hard enough. There's a lot of pressure inside the core of a planet...