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Smallest Exo-planet Found

Ignasi Ribas with simulated picture of the new planet.  Image Credit:  REUTERS/Sergio Perez
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

About 

Nancy Atkinson is Universe Today's Senior Editor. She also works with Astronomy Cast, and is a NASA/JPL Solar System Ambassador.

Comments on this entry are closed.

  • Donut April 10, 2008, 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?

  • Jim (himself) April 10, 2008, 8:34 AM

    Donut,
    There would probably be nothing above a life form similar to an amoeba or a very thin pancake.

  • Jim Baerg April 10, 2008, 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.

  • Neko April 10, 2008, 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..

  • Some Guy April 10, 2008, 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”?

  • Mr. LAME April 10, 2008, 12:57 PM

    great to see some catalan astromers
    visca catalunya !

  • Nick Mascall April 11, 2008, 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.

  • Fabio Knopf April 11, 2008, 8:06 AM

    Great post Nick!

    Thanks!

  • TGW April 11, 2008, 8:46 AM

    narly!

  • RBH April 11, 2008, 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.

  • ScepticTim April 11, 2008, 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!

  • Steven Spowart February 14, 2009, 8:58 PM

    If we are on the verge of discovering earth like planets, how long before we are able to detect the presence of an extra terrestrial satelite system in orbit of it?

    And how exacly do they manage to work out what gasses make up the atmosphere of a planet when it is 50 light years away?

  • zafdr March 3, 2009, 10:14 AM

    :( :) :P :D :S

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