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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 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. We've got a ways go to if this is the most earthlike one. This was detected via the "wobble" method; how advanced are other methods of extrasolar planet detection methods?
The team measures a minimum mass for the planet of 5.9 Earth masses
It seems that planet's gravity is quite big for "earthlike" planet. Is life possible at all under such gravity? Any examples?
which is only 15 light years away
So why not send some radio traffic which would obviously not be of natural origins. Surely 30ish years isn't that long to wait for a reply? (assuming the place has lifeforms which developed radio...)
Trolling is a art,
Its Earth-like because it is a rocky, rather than gaseous planet. Astronomers have to find new planets by detecting the wobble in the path of the star being orbited, which is caused by the orbiting planet. The bigger the planet, the bigger the wobble, so big gas giants were the first planets found. The fact that it completes an orbit in two days also helps as you don't need to collect years of data in order to see the wobble. So it's really not very Earth-like, but its the closest thing found so far, outside of our solar system.
I am not an astronomer, but isn't mars more earthlike than that?
It is easier to believe the wobble is due to some temporary imbalance within the star, than to believe that a planet that size formed that close in. The chances the star "captured" it that close are also unbelievable.
Maybe something big actually hit the red dwarf and is slowly finding its way to the center of gravity.
Seems to me that this is the core of one of those too-close Jovian types, and not a started-out-that-size planet.
This planet's "year" is two Earth days. But how large is its orbital radius (other than "so close to the star's surface")? So, how fast is its orbital velocity? Is it so fast that the centripetal "force" (illusion) of its orbit is significant, compared to its (greater than Earth) gravity?
In fact, even Earth seems like it should have centripetal effects. We rotate 1000MPH; we're orbiting at something like 70,000MPH, right? Shouldn't Earth gravity be balanced by detectable acceleration along the tangents to those circular motions?
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make install -not war
After reading the article it seems like they "discovered" the planet simply by observing the star and two very large jupiter type gas giants that are circling the star. By the orbits of the planets and the "wobble" of the star they have determined that there must be another planet of the specified size and orbit.
So essentially this planet was discovered solely on observation of its gravitational effect on other planets. In other words the scientists built a computer model which includes the star and two visible gas giants, and found a planet which they could insert in it so it causes the star and the gas giants to behave as they in the model as they do in observation. Then they declared that they have discovered a new planet.
How did they know it was a rocky planet? Well, correct me if i am wrong but it seems like they decided that by elimination -- the planet is too small to be a gas giant and too close to the star to have anu liquid water on it. Therefore, it must be a rocky planet.
Admittedly I do not know much about modern astronomy but all of this is a little troubling. I mean should we not obtain direct observation from something before we proclaim it "discovered"?
I am sure modeling solar objects is very useful but modeling is limited to our current knowledge. If rely too much on modeling we will never discover anything that we do not already know about.
That leads to a very interesting thought.
Just how much of modern culture as we know it is based, either directly or indirectly, upon how quickly the Earth revolves around the sun?
If we ever DID colonize a different planet, how would our culture adapt? Would it, either immediately or eventually, migrate itself so that annual events follow the revolutions of the new planet, or would they maintain the annual timeline of Earth?
The favourite possibility of sci-fi authors for life on planets like this is in the polar "twilight zones". It'd be a hard, hard life (the winds would be killer hot or cold) but life has been found on some pretty strange places on Earth...
Any sufficiently advanced technology is indistinguishable from a rigged demo
--Andy Finkel (J. Klass?)
...with slightly lower surface temperatures, as this one ranges from 200 to 400 degrees, obviously uninhabitable. If they could locate one that closely mirrors the earth as far as environmental and atmospheric conditions, then we could start focusing on how to start migrating humans via cryogenic and hyperspace travel to said planet. Would solve earth overpopulation problems.
Meh.
Instead of moderating you down, I'm just going to comment here...
Yes, our Sun wobbles like that. Its wobble is done mostly by Jupiter, but the Earth contributes as much as +/- 3 meters/s, if I recall correctly. And for these guys, it's not impossible to detect such perturbations.
That said, the wobble method (Dopper detection) is good for all sizes of planets. If it is not a single planetary system, that will show up in the radial velocity curve (like it does here..non sinosoidal curve, I mean).
What you should be asking is this: how the hell do they know about the radius of the planet? The mass isn't too hard to determine (Kepler's law would tell you); but the radius isn't. Not in the accuracy claimed here (2 earth radius). Since I don't have an access to the article yet, it's hard for me to judge the accuracy of the radius value. Nontheless, that's where all of you should be pondering about, not about the wobble method.
Amazing that FARK readers are pointing this out better than Slashdot readers...what did we go wrong?
It's a massive rocky extrasolar planet, with much higher gravity than Earth's, orbiting extremely close to its parent star, an M-class red dwarf -- A RED SUN.
Sound familiar? Perhaps, even, super?