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Scientists Discover Exoplanet Less Than Twice the Mass of Earth
Snowblindeye writes with this excerpt from the European Southern Observatory:
"Well-known exoplanet researcher Michel Mayor today announced the discovery of the lightest exoplanet found so far. The planet, 'e,' in the famous system Gliese 581, is only about twice the mass of Earth. The team also refined the orbit of the planet Gliese 581 d, first discovered in 2007, placing it well within the habitable zone, where liquid water oceans could exist. Planet Gliese 581 e orbits its host star — located only 20.5 light-years away in the constellation Libra ('the Scales') — in just 3.15 days. 'With only 1.9 Earth-masses, it is the least massive exoplanet ever detected and is, very likely, a rocky planet,' says co-author Xavier Bonfils from Grenoble Observatory. Being so close to its host star, the planet is not in the habitable zone. But another planet in this system appears to be. ... The planet furthest out, Gliese 581 d, orbits its host star in 66.8 days. 'Gliese 581 d is probably too massive to be made only of rocky material, but we can speculate that it is an icy planet that has migrated closer to the star,' says team member Stephane Udry. The new observations have revealed that this planet is in the habitable zone, where liquid water could exist. '"d" could even be covered by a large and deep ocean — it is the first serious "water world" candidate,' continued Udry."
I always hear about these sorts of discoveries, of new planets more and more similar to earth, but having almost no astronomy background, I have no idea how significant they are.
How much do we really know about these planets, and how much is guessing? How close are these planets, really, to earth?
Gliese 581 d is probably too massive to be made only of rocky material...
Even if it isn't habitable, it might still be large enough to have a habitable moon perhaps?
I Am My Own Worst Enemy
The science of extra-solar planet detection is very interesting, but speculation about surface conditions that might exist doesn't reflect the science at all, it's just fodder for the media and bloggers.
The only things we know are extremely rough estimates of orbital parameters and mass, although the host star is well characterised. The speculation is conjuring up quite specific images in people's minds, and while fun, they're not justified. It's leading people without an astronomy background astray.
"The question of whether machines can think is no more interesting than [] whether submarines can swim" - Dijkstra
1) Considering how many planets we have looked at and that we can't find life on any of them this makes Earth very extraordinary.
The only reason we are able to detect life on Earth is due to proximity - so you're just as guilty of jumping to conclusions as the GP. We've found planets that differ wildly from Earth because the easiest planets to detect are the fuck-all-huge ones. Just because we haven't observed Earth-like planets yet does not mean they aren't all over the bloody place. They're just rather hard to spot with current technologies.
If we do an absorption spectrum reading of the atmosphere, which can be done at astronomical distances, and find free oxygen that would be a strong evidence for life on that planet. Oxygen is so reactive that it wouldn't exist very long in a planet's atmosphere before combining with something, unless here is a process like life to replenish it.