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Space Science

Astronomers Find Smaller Extrasolar Planets 25

Posted by timothy 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.

"

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Astronomers Find Smaller Extrasolar Planets More

Astronomers Find Smaller Extrasolar Planets

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  • Anyone else laughed at the art? (Score:4, Interesting)

    by SmallFurryCreature ( 593017 ) on Wednesday September 01, 2004 @12:05AM (#10125422) Journal
    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.

    • 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

    • 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.'
    • 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.

    • 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?

    • 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

  • I just read about this on the NYT... (Score:4, Interesting)

    by drinkypoo ( 153816 ) <drink@hyperlogos.org> on Wednesday September 01, 2004 @01:17AM (#10125744) Homepage Journal

    ...with a little help from bugmenot [bugmenot.com]. 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?

  • It will be a long time . . . (Score:3, Insightful)

    by kalidasa ( 577403 ) * on Wednesday September 01, 2004 @06:27AM (#10126497) Journal
    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. . .
    • 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
  • 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

    • 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.
      • 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 a

  • "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?

    O
    • 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

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