Smallest Exo-planet Found
Written by Nancy Atkinson
We’re getting closer to finding an Earth-like planet out there in the universe. Spanish astronomers announced the discovery of the smallest exo-planet found to date, located 30 light years from earth. "I think we are very close, just a few years away, from detecting a planet like Earth," team leader Ignasi Ribas said at a news conference on Wednesday April 9, 2008. The newest planet, "GJ 436T" was discovered by a team led by Ribas through its gravitational pull on other planets already discovered around the same star in the constellation of Leo.
The planet has a mass five times the size of Earth, which makes it the smallest extrasolar planet among the roughly 300 identified so far, Ribas said. The astronomers believe the planet could possibly be a rocky, Earth-like planet because of its size. Most of the planets found so far are gas giants like Jupiter.
But Ribas said the new planet is uninhabitable due to the close distance that it orbits its star, which is far less than that between the earth and the sun. Planet GJ 436 orbits close to its small, relatively cool star once every 5.2 Earth days and rotates every 4.2 Earth days.
This latest planet was found by analyzing distortions in the orbit of another, larger planet around the star GJ 436, a technique similar to that used more than 100 years ago to discover Neptune.
"Planets with a mass similar to Earth situated at a distance from their star which allows liquid water on the surface, in other words, a habitable planet, we're probably a bit further from (discovering those), but we surely will in a decade," said Ribas of Spain's CSIC scientific research institute.
Original News Source: Reuters
Filed under: Astronomy
April 10th, 2008 at 7:47 am
Exciting stuff, I just wish they gave these things better names. One question though:
If a planet five time the size of Earth was at an acceptable distance from its star, what are the consequences for life in that sort of gravity?
April 10th, 2008 at 8:34 am
Donut,
There would probably be nothing above a life form similar to an amoeba or a very thin pancake.
April 10th, 2008 at 8:56 am
Assuming the planet has the same density as earth, it's fairly easy to calculate that the surface gravity is 1.7 x the surface gravity of earth.
The greater pressure in the center of the planet would likely increase the overall density given similar composition, but the the planet could be made of lighter elements on average than earth (less iron), so a gravity in the range of 1x to 3x earth's seems likely.
Lot's of people can walk (rather haltingly) while carrying extra weights equal to their own body weight, so I think animals evolved in the higher gravity would be about as complex as earth animals but of a more squat design.
April 10th, 2008 at 9:16 am
Well for us, evolved beings, could be easy.. now think of 4 billions years of evoulution on that conditions and ask yourself if something like us could have evolved..
about the names.. everyday i'm more sure they use Stargate SG1 names..
April 10th, 2008 at 9:40 am
Neko,
Do you mean names like P3X-639 or whatever names the SGC gives planets, or actual names like, "Chulak"?
Or maybe "Abydos"?
April 10th, 2008 at 12:57 pm
great to see some catalan astromers
visca catalunya !
April 11th, 2008 at 3:20 am
This planet is designated GJ 436c - not GJ 436T, as the article states.
Current astronomical practice is to label exoplanets with the star designation (GJ 436 in this case) followed by a lower-case letter from the alphabetic sequence starting with 'b', in order of discovery. Since this is the second planet discovered around GJ 436, it becomes 'c'.
Why not start the sequence with 'a'? Because there's at least one star catalogue where stars inserted into an existing number sequence have been distinguished by adding 'a' to the number. For example; LHS 1095 and LHS 1095a are two different stars.
Why lower-case letters? Because upper-case letters (A, B, C etc.) are used to label individual stars which are components of a multiple system (binary or larger). Once again, the letters are assigned in order of discovery, which usually means descending order of brightness.
To give a completely hypothetical example; suppose LHS 1095, which I mentioned above, was discovered to have a planet orbiting it. that would then be LHS 1095b. A second planet would be LHS 1095c, and so on. If LHS 1095 was discovered to be a binary system, the two stars would be labeled LHS 1095A and LHS 1095B. If planets were then discovered around the A component, these would be LHS 1095Ab, LHS 1095Ac and so on.
April 11th, 2008 at 8:06 am
Great post Nick!
Thanks!
April 11th, 2008 at 8:46 am
narly!
April 11th, 2008 at 10:19 am
Nancy, your article states "The planet has a mass five times the size of Earth". It would be interesting to see the error limits on this estimate. At least two similar sized planets have been previously discovered.
To quote from the paper :"The habitability of Super-Earths in Gliese 581" (arXiv:0705.3758v2 [astro-ph] 6 Jul 2007), "Very recently, Udry et al. (2007) announced the detection of two super-Earth planets in this system, Gl 581c with a mass of 5.06 Mearth with a semi-major axis of 0.073 AU, and Gl 581d with 8.3 Mearth and 0.25 AU."
While I do not have error bars on this estimate, Gl581c would seem to be as small as the reported planet in your article. Also, from the paper "Discovery of a cool planet of 5.5 Earth masses through gravitational microlensing"
(J.-P. Beaulieu1,4 et. al.: 26 Jan 2006 issue of Nature) "Here we report the discovery of a 5.5 (-2.7,+5.5) Mearth planetary companion at a separation of 2.6(-0.6,+1.5) AU from a
0.22 (-0.11,+0.21) solar mass M-dwarf star."
At the lower limit of the error bar on this estimate (5.5 - 2.7 = 2.8 Mearth) this planet could be smaller than the one reported here!
April 11th, 2008 at 5:01 pm
I call your attention to Phil Plait's post on this find. GJ 436T is far from the smallest exoplanet so far found.