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Detecting exoplanets moons

  1. Feb 17, 2009 #1
    how far are we from detecting a moon around an earth sized planet in another star system?

    i read an article recently (http://www.newscientist.com/article...e-sun-and-moon-the-same-size-in-the-sky.html") about how the moon being so close to earth wasn't, or doesn't appear to be, a very likely event. since there was a low probability of our planet having our moon it seems it was actually important for life to form here in the first place (tides, etc...).

    it got me wondering how far technology has to develop in order to find a planet the same size of earth, in the same type of orbit, around an identical star to the sun, with a moon the same size of earths on the same type of orbit?

    do we need to detect the moon? what comes first, detecting wavelengths of light reflected from the surface of the planet, or detecting a planets wobble due to its moon? if we could detect light from the planets surface would we be able to detect any plant life etc?

    what about detecting oxygen in the atmosphere?

    i cant think of anything more exciting than detecting these kind of things and am basically wondering how much we will find out, and the likelihood we will find strong evidence of extra terrestrial life, within my lifetime.
    Last edited by a moderator: Apr 24, 2017
  2. jcsd
  3. Feb 17, 2009 #2


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    The types of detection techniques we use today, radial velocity and transit, would not be very good at revealing moons. It will likely take a new technique using new technology.
  4. Feb 18, 2009 #3


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    It's true that the Earth's satellite situation is quite unique. First, the mass of the moon is very comparable to that of the Earth, and it is in an extremely stable orbit as well. (Coincidentally it covers about the same angle in the sky as the sun, too!).

    If you're going to cherry pick planets in order to find one with all the parameters you described, we would need to extend our search radius by orders of magnitude probably before we found one. This alone, let alone detection techniques, would be an extreme technological undertaking.
    Last edited by a moderator: Apr 24, 2017
  5. Feb 27, 2009 #4
    would it be possible to use interferometry to 'see' an exoplanet?
    i mean to cancel out the light of the sun i know it would be difficult especally in the visible but is it theoretically possible?
  6. Feb 27, 2009 #5


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    There are projects in development that will use nulling interferometry to cancel out a star's own light and hopefully be able to image planets directly. This would allow us to analyse the atmospheres of such planets for gasses that indicate signs of life.

    See (for example):

    Last edited by a moderator: Apr 24, 2017
  7. Feb 27, 2009 #6
    sweet i hope they can do it :)
    and i'm glad it wasn't a silly idea!
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