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30 Billion Earth Sized Planets?

Posted by michael on from the spaceward-ho dept.

Tha_Chaotic_1 writes "The BBC is running a story about a prediction that there are around 30 billion earthlike planets in the universe. This comes following the discovery of the 100th gas giant outside our solar system. Optimistic?"

7 of 58 comments (clear)

  1. gamma-ray emissions by bofh31337 · · Score: 3, Interesting

    I think this number is a bit high. I'm not sure they've taken into account that solar systems too close to the center of the galaxy due to the "galactic doughnut" effect. Anything to close to the center of the galaxy, in the doughnut hole, would not be habitable due to excess bombardment of gamma-rays.

    1. Re:gamma-ray emissions by Mr.Intel · · Score: 3, Interesting
      If life can adapt to that, why not to a few gamma rays?

      Poking into the realm of science fiction, one would have to presume one of two things for this to happen. Either these life forms would have some sort of natural protection from such radiation or have developed some technology that protects them. Or their life is based on something other than carbon (silicon?). The reason for this is that all carbon based life is easily damaged by high energy light waves. Indeed, most non-metals tend to break down their molecular bonds when exposed to gamma rays. Either way, despite the tenacity of life, it would require a large leap of faith to assume that this is the case.

      --
      ASCII tastes bad dude.
      Binary it is then.
  2. Re:How Far Away? by capt.Hij · · Score: 3, Interesting
    With the new world, astronomers say that they have just about finished surveying all the Sun-like stars out to a distance of 100 light-years from Earth.

    Looks like they *think* that they've poked around in a 100 light year radius of earth. Given the extremely poor precision in which distances are measured this may be a bit optimistic.

    Also from the article:
    And if stellar statistics gathered in our local region of space are applied to our galaxy of 300 billion stars, then there may be 30 billion Jupiter-like worlds and perhaps as many Earth-like worlds as well.

    Since our universe is not uniform this may be an abuse of statistics. They've only looked at one very small corner. This is a heck of a Monte-Carlo simulation, though!

  3. Optimistic? Probably. by Pembers · · Score: 2, Interesting

    Especially when you consider that no-one claims to have seen an Earth-sized planet orbiting another star. But then, no-one would claim that meant there were no such planets.

    The figure of 30 billion Earths appears to be extrapolated from two things. One, that the galaxy contains an estimated 300 billion stars. Two, that of about 1,000 stars surveyed, astronomers have detected planets orbiting about 100 of them, or 10%.

    If this holds for the galaxy as a whole, then 30 billion stars have planetary systems. To say that this implies an average of one Earth-sized planet per planetary system sounds like stretching the data. Sure, we have some theories on how planets form, and every new discovery presents much-needed data to test them, but until someone actually detects a planet the size of ours, we have no idea how common they really are.

    --

    Just another wannabe fantasy novelist...

    1. Re:Optimistic? Probably. by JumpinJohnny · · Score: 2, Interesting


      If this holds for the galaxy as a whole, then 30 billion stars have planetary systems. To say that this implies an average of one Earth-sized planet per planetary system sounds like stretching the data.
      </quote>

      Not necessarily. 10% of the surveyed systems contain gas giants. There may very well be many more systems that only have smaller planets. The planets in those systems are still undetectable with our current technology.

      Johnny

    2. Re:Optimistic? Probably. by wom · · Score: 2, Interesting

      Of these detected planets, _some_ are large gas type planets close to the star, which would preclude there being an earthlike planet there. Our theories are based on a sample space of one, and "wobbles". OTOH, it well could be that there are earthlike planets attached to stars that don't have giants orbiting them. IMHO, there is no reason to make any prediction based on this data.

      PS. Don't confuse "galaxy" with "universe"

      --
      Trouble, a mistake or fun, your choice
  4. it's worse than that by Tumbleweed · · Score: 3, Interesting

    There's also a theory that says that you may well need to have at least one gas giant further out from your star to help deflect space schmutz from wiping your species out too early. Since we have 4 very large planets further out from our planet, we've got a lot of gravity wells helping to keep the inner system cleaner than it would normally be. Then again, this may be a rather common configuration - if a star forms and a gas giant forms, then the eddys between the forming star and forming gas giant may just be what turns into a smaller planet. Where's a Wayback Machine when you need one? *sigh*