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Rocky Planet Discovered
Fraser Cain writes "Astronomers have discovered a rocky, terrestrial planet orbiting a nearby star, Gliese 876. The planet has approximately 7.5 times the mass of the Earth, double its radius, and orbits its parent star once every two days. This is the most Earthlike extrasolar planet discovered so far." Reader Karthik Narayanaswami points out that "the planet was discovered by the famed Berkeley astronomer Geoff Marcy," and adds a link to the news release from Berkeley.
The thing has gotta be mighty close to the star. Mercury orbits in 60 days, right? This thing may not be a gas giant, but it must totally bake on the sunny side, and aren't there going to be some horrendous tidal forces with an orbit that close? It probably has no shortage of volcanism. Hey! It's Vulcan, maybe... if it can hold an atmosphere without having the stellar wind blow it all away. Whatever, it can't be Earth-like.
For all intensive purposes, "whom" is no longer a word. That begs the question, "who cares"?
Gravity is only 1.8 from normal - I believe you can get used to it. Meanwhile surface is 3.2 times larger, so if it could be terraformed it will hold a lot of people from our overcrowded Earth.
Of course I put many questions aside like how would they get there, does it have any continents, how sensitive processes like childbirth are to the gravity, does its atmosphere shield properly from radiation, isn't it too cold/hot there (although this can be fixed) etc etc...
This is pretty simple. Surface gravity for spherically-symmetrical masses scales linearly with mass and inverse-square with radius. The mass makes gravity 7.5 times higher, while the radius would make it 4 times lower, for a total surface gravity of about 1.9G.
Patrick Doyle
I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
The majority of scientists consider the 'wobble' to be an effect of the planet(s) revolving around the star. If you don't accept that planets are the most probable cause, then what your best guess as to what is the cause of the 'wobble'? If you're answer is "I don't know, but they don't know either.", then I think you simply don't know enough to be critical of these PhDs who have made this discovery. (But then again, this is Slashdot, right?).
I think you over-simplify your estimation of how they decided it was rocky. They use, as a model, what they've found in our solar system, as well as basic physics.
As far as I know, this star is simply too faint to be directly observed for planets and detecting the wobble is the best method of detecting the likelyhood of a star system containing planets. If you have a better method of detection other than declaring "your method is not good enough!", please let the scientific community know. They could then use your help and your insightful powers of posting on Slashdot.
I watched the live webcast of the announcement of their discovery as they answered questions from the rest of the astronomical community (via phone/e-mail). Believe me, these people who announced this discovery aren't stupid, and they are using the best scientific theory they have at hand (with 3 years of data supporting their theory, yeah they waited that long before announcing this).