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Astronomers Find Smaller Extrasolar Planets

Posted by timothy on from the spaceporn dept.

SABME writes "NASA has announced the discovery of a new class of extra-solar planets. Here's a link to the NASA news release. These planets are only 10-15 times bigger than Earth; how far off are we from discovering Earth-sized planets orbiting other stars? Future NASA missions aimed at broadening these discoveries include Kepler, the Space Interferometry Mission and the Terrestrial Planet Finder. More info available at NASA's Extrasolar Planets webiste.

"

19 of 25 comments (clear)

  1. Anyone else laughed at the art? by SmallFurryCreature · · Score: 3, Interesting
    Artist impression of what? NASA hasn't detected the planet. It has detected the influence of the planet. Doesn't even have to be a planet. It could be a really heavy asteroid. Or a cloud of them. Or something entirely different. Maybe some stars just like to wobble.

    All they detected is that it looks like the suns in question have something spinning around them. When they actually photograph them or detect the planets themselves THEN and only then can we start to speculate what they look like. For now it is pure speculation that they are in fact planets.

    --

    MMO Quests are like orgasms:

    You may solo them, I prefer them in a group.

    1. Re:Anyone else laughed at the art? by AresTheImpaler · · Score: 1
      Artist impression of what? NASA hasn't detected the planet. It has detected the influence of the planet. Doesn't even have to be a planet. It could be a really heavy asteroid. Or a cloud of them. Or something entirely different. Maybe some stars just like to wobble.

      I'm pretty sure it's just the Death Star

    2. Re:Anyone else laughed at the art? by v1x · · Score: 1

      Agreed. But then again how many other such phenomena are that easy to capture by conventional means? Whether its the best radio-telescope or the best electron microscope, some things have to be extrapolated.

      Take the example of the structure of benzene or that of DNA: both were predicted at some point and proven later on. If having an artistic impression allows us to test & validate our hypotheses when we have the means, then I see that as a 'Good Thing.'

    3. Re:Anyone else laughed at the art? by Lars+T. · · Score: 1
      Doesn't even have to be a planet. It could be a really heavy asteroid.

      Well, really heavy asteroids several times the mass of Earth are called planets.

      --

      Lars T.

      To the guy who modded me down from perfect to terrible Karma - Apple haters still suck

    4. Re:Anyone else laughed at the art? by gl4ss · · Score: 1

      that's why it's an artistic impression and not an "enhanced photo" or some crap.

      **All they detected is that it looks like the suns in question have something spinning around them.** well if they can detect that they can say they're planets or planetlike somethings. and why would we need to speculate only after they got a good clean pic of the thing? what point would it be _speculating_ about something you know?

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      world was created 5 seconds before this post as it is.
    5. Re:Anyone else laughed at the art? by Silverlancer · · Score: 1

      First of all, large rocks going around stars are known as planets. Second of all, any asteroid larger than about 200km wide will settle into a spherical shape. Ceres is one of the smaller examples. Earth, Mars, Pluto, our Moon, and other large objects in our solarsystem are other examples. Third of all, planets that size tend to gather a LOT of gas during solarsystem formation. So we know that its round, its big, and its covered with a massive gas atmosphere.

      That's pretty close to that concept art IMO!

  2. Re:Class M? by gnarly · · Score: 4, Interesting

    Yes, but are they Class M ?

    Actually, yes. The star that is. What is remarkable is that one of these neptune-mass planets orbits a Class M star, the smallest and faintest in the standard stellar classes OBAFGKM. It is only the 2nd M star to harbor planets, even though hundreds have been studied.

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  3. I just read about this on the NYT... by drinkypoo · · Score: 3, Interesting

    ...with a little help from bugmenot. One thing in their article that struck me as unexplanatory is the statement that finding these planets suggests we will be finding some earth-mass planets one of these days soon. Guess I should've submitted the story, eh? Especially since the assignment was on writing summaries.

    The NYT article doesn't say the planets are smaller than neptune or jupiter, as the NASA article does, but neither article explains why these planets are signs of Earthlike planets. Can someone fill me in?

    --
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    1. Re:I just read about this on the NYT... by astroboscope · · Score: 4, Informative
      neither article explains why these planets are signs of Earthlike planets

      I think they're just pleased that they've found a couple of sub-Saturn sized planets. i.e. planets at least as big as Jupiter were first and easiest to be found, then came Saturns, and now, as they hoped, the trend has continued to Neptunes, buoying their aspirations to find even smaller planets.

      --
      If we were ants living on a Rubik's cube, differential geometry would be a little more confusing.
    2. Re:I just read about this on the NYT... by ramunas · · Score: 1

      IIRC then if the planets mass is less than some number, then they fail to become gas giants, and are therefore solid, this is what they consider Earthlike

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      ./R My blog
  4. Re:Class M? by Lars+T. · · Score: 1
    A Terrestrial planet is catagorized by an abundance of surface water [...] Examples of Class M planets include: Earth (Sol III), Vulcan

    Tsk. From the description of Vulcan linked from that page:

    Vulcan's climate is generally harsh, with much of the surface consisting of large deserts or mountain ranges.
    Doesn't sound like "abundance of surface water" to me ;-)
    --

    Lars T.

    To the guy who modded me down from perfect to terrible Karma - Apple haters still suck

  5. Re:Class M? by ManitobaMoose · · Score: 1

    if we're talking of mu Arae, well it's not a M-spectral type star, but a G3V with 1.9times Sol metallicity. luminosity is 1.7 Sol mass 1.32 Sol http://www.solstation.com/stars2/mu-arae.htm

  6. It will be a long time . . . by kalidasa · · Score: 2, Insightful

    Before they find a genuinely earth-like planet with this technique - with the radial velocity technique you find big close planets first, later big distant planets and medium-sized close planets, etc., and small close but not too close planets last. Not a criticism of the astronomers; it's amazing that they can find even a very close Neptune-sized planet with this. . .

    1. Re:It will be a long time . . . by Doctor+Fishboy · · Score: 1

      Just to add to what you said, the radial velocity technique starts to get into trouble with metal-poor stars or stars that have periodic fluctiations in their chromospheres. The reflex velocity signal of a earth mass planet is much smaller than the fake signal caused by turbulence in the star's atmosphere.

      Cheers,

      Dr Fish

  7. Somebody's confused by Markus+Registrada · · Score: 1
    When they say "16 times as large as Earth", they don't say what they're measuring. Since they detected them by gravitational perturbation, I'm guessing they mean "16 Earth masses". In a rocky planet approximating Earth's density, that means just pow(16,0.33)=2.5 times the diameter, or 20k miles to Earth's 8k. That's really a lot closer to Earth's size than it might have seemed. At the same density, surface gravity would also be only 2.5G, to Earth's 1G.

    On such a planet, albeit one not so close to its star as the ones they have found so far, it is easy to imagine creatures walking on stout legs -- never mind the insects and sea creatures that wouldn't even notice the "extra" weight.

    1. Re:Somebody's confused by Shihar · · Score: 1

      I am fairly certain that they mean 20 times Earth's radius if they are calling it a Neptune like planet. Recall that the strength of gravity increases to the cube of the radius (assuming constant denisty). In other words, you can fully expect to be crush flat on this planet and for its surface to be rather toasty from the pressure of its own atmosphere. Clearly that doesn't mean that no life will exist, but certainly it won't be life as we know it.

    2. Re:Somebody's confused by Euphonious+Coward · · Score: 1
      Now I know who's confused.

      I found another report indicating that, as suspected, they really were talking about mass. Neptune is not, in fact, over 136,000 miles in diameter. (Neither is Jupiter.)

      The strength of gravity doesn't grow as the cube of the radius. It grows linearly with the mass, and as the inverse square of the radius. ("Inverse-square law", remember?) The radius grows as the cube root of mass, given constant density. That means that, assuming earth's density, the gravitational force at the surface matches the radius: 2.5G, in this case.

      Double the density (e.g. in case it's made of iron) and you still get only ~4G.

  8. why does size matter? by nusratt · · Score: 1

    "These planets are only 10-15 times bigger than Earth"

    Why do we assume that life is most likely where gravity is close to ours?
    Consider the organisms discovered only in the last 30 years,
    which thrive in environmental extremes of heat and pressure.

    And it need not be non-"intelligent" life:
    consider the pressures sustained by sperm whales and giant squid.

    For that matter, is it guaranteed that large diameter = crushing gravity?
    Might there realistically be a planetary giant with significantly lower density?

    Or might crushing gravity be reduced by the gravity of surrounding bodies,
    e.g. moons or binary/ternary stars,
    or by a single star orbited by a non-rotating planet?

    1. Re:why does size matter? by stevelinton · · Score: 2, Insightful

      Planets much larger than Earth will inevitably be either

      a) much hotter than Earth (which is the case with these ones, I think)

      or

      b) mostly made of hydrogen and helium, like Jupiter, Saturn, Uranus and Neptune

      At our temperatues, a massive planet would captuse lots of hydrogen and helium from the initial nebula and never lose them.

      In either case, no life remotely like us could exist. Of course one cannot rule out life based on some exotic chemistry, but the absence of evident life on Mercury or any of our own gas giants is a small piece of negative evidence.