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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.
Oh wait... you said Rocky Planet.
Here is the link to the Berkeley press release and information on Berkeley astronomer Geoff Marcy.
And oh, looks like Slashdot is continuing to mirror Boing Boing.
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?
With a new year every two days, everyone would be broke buying birthday cakes.
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"?
If it is, does that mean Spock mates once every 14 days?
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,
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...
Its always interesting when we find these new planets in other systems, but the wobble method is just not effective for finding an earthlike planet. For starters, have you ever noticed all the planets found have extremely quick orbits (1 year = 2 days) etc. And infact the longer their year is the bigger the planet is (because although the wobble doesn't occur as quickly it is more pronounced. If a planet were to have orbits similar to ours it would take nearly 2 years to see one wobble back and forth. Sure its neat to find new planets but I don't think we need to be spending all our time looking for wobbling stars. For every star that wobbles there are probably more just sitting still with planets around them more similar to ours that we just cannot detect.
Also, I tend to think if you see a start wobbling back and forth its because there is one large mass in its orbit affecting it, as opposed to many planets balancing things out at various points around the start. Does our Sun wobbel like this? I am not sure, but if not, it hardly seems a good measure to find an earthlike planet, but rather a good way to find large sole planet systems.
I am not an astronomer, but isn't mars more earthlike than that?
Adrian!!!
"It's a tarp!" -- Dyslexic Admiral Ackbar
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?
--
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.
do not try to pick up fight with the natives ...
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?)
No.
A body moving in a circle of radius R at a uniform speed V experiences an acceleration a = (V*V)/R towards the center of the circle. In neither of the cases you mention does any centripetal acceleration come close to the local gravitational acceleration at the surface of the planet.
Case 1: The Earth: orbital speed V = 30 km/s, and R = 150 million km, so (V*V)/R is of order (10^8)/(10^11) m/s^2, or about 10^(-3) m/s^2. The local gravitational acceleration is about 10 m/s^2, of course. If you speak of the Earth's rotational motion at the equator, then very roughly V = 500 m/s and R = 6,400,000 m, so (V*V)/R has magnitude roughly (2.5 x 10^5) / 6.4 x 10^6 = 0.03 m/s^2; again, much less than 10 m/s^2 due to the gravitational pull of the Earth.
Case 2: The new planet. Its orbital radius is about 2 billion meters, so the circumference is about 7 billion meters; if it travels that distance in a period of 2 days = 170,000 seconds, then it speed is about V = 40,000 m/s. The orbital centripetal acceleration is therefore of order (16 x 10^8)/(2 x 10^9) = 0.8 m/s^2. That's much larger than the Earth's orbital centripetal acceleration, but still far less than the likely gravitational acceleration at the surface (or cloudtops) of this planet.
Michael Richmond "This is the heart that broke my finger."
mwrsps@rit.edu http://stupendous.rit.edu
Tell me when they find the Bullwinkle planet. Bullwinkle was always funnier.
Is there some physical reason why massive rocky planets cannot form, or are we assuming that massive planets in other solar systems must resemble massive planets in our solar system?
...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.
Case 2: The new planet. Its orbital radius is about 2 billion meters, so the circumference is about 7 billion meters; if it travels that distance in a period of 2 days = 170,000 seconds, then it speed is about V = 40,000 m/s. The orbital centripetal acceleration is therefore of order (16 x 10^8)/(2 x 10^9) = 0.8 m/s^2. That's much larger than the Earth's orbital centripetal acceleration, but still far less than the likely gravitational acceleration at the surface (or cloudtops) of this planet.
But this is more than sufficient that if there were intelligent life (fabulously unlikely) then they would quickly notice that things were a few percent lighter at night than during the day.
The planet has about 7 times the mass of Earth and about twice the radius, so the surface gravity will be...pause for algebra...about 2g ~ 20 m/s**2. At night, the orbital centripetal acceleration acts against the surface gravity, so it would be a minimum at midnight of 19.2 m/s**2, and during the day they act together for a max at noon of 20.8 m/s**2, or a little less than a 10% difference.
This is conceptually closely related to tides, and this is another way of pointing out that the tidal effects on such a world are going to be wickedly large.
Blasphemy is a human right. Blasphemophobia kills.
I can hear it screaming now...
All the worlds indeed a
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?
The wobble method of planet detection is more effective for lower mass stars. A planet of a given mass will move a smaller M star more than a bigger G star like the Sun. Plus on top of that, only 8% of stars in the galaxy are G class or bigger, so as we look outwards the closest stars tend to be M and K which biases the planet finds to lower mass stars. If you use the occulation method (the planet covers part of the star as it passes between us and the star), again in the M star case, the planet would cover a bigger fraction of the star's area since the red dwarf is so small. If some alien astronomer looked at the solar system and the earth passed in front of the Sun, the Earth would only cover 1/10000 th the area of the sun, but if earth orbited a red dwarf it would be more like 1/200 (0.5%) -- much easier to detect the change in light. Mark
From TFA:
Um, no, that's not true - there certainly are bacteria which can survive these temperatures and have adapted to them (those living near hydrothermal vents at the bottom of the ocean, for example). Whether this new planet could (even theoretically) host life is another question entirely, of course, but the statement that we do not know life that can endure such temperatures is simply not true.
quidquid latine dictum sit altum videtur.
Apart from the one we're standing on? :)
... is 6378.5 kilometers, not 12756.3 as you have above. The correct values for the force on a 1kg mass on the surface are:
Earth: 9.785 N
New planet: 18.366 N
So the grandparent poster is correct, the surface gravity would be about 1.9 times that of Earth.
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....
I'm going to guess there is no night and day. The plant is probably tidally locked.
Patrick Doyle
I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
Assume I was drunk when I posted this.
An alternative method is to look for eclipses of the planet passing in from its stars. About 5% of the planets have been discovered this way. One estimate is about one in two hundred stars have suitable orientations and plantary systems for this method, if one could observe them long enough. A @hundred megapixel space probe called Kepler might be launched around 2008 to observe light curves of several hundred thousand stars for several years. This might find dozens of eclipsing planets plus understand the abundance of planets.
Except that out of those, only microlensing is likely to detect non-giant planets (orbiting non-pulsars) and it's based on random luck.
In practical terms, if you want to find earthlike planets, you use the doppler method.