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Fwd = There could be billions of Earths out there

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  • Frits Westra
    Forwarded by: fwestra@hetnet.nl (Frits Westra) URL: http://news.bbc.co.uk/hi/english/sci/tech/newsid_2078000/2078507.stm Original Date: Wed, 3 Jul 2002
    Message 1 of 1 , Jul 3, 2002
      Forwarded by: fwestra@... (Frits Westra)
      URL: http://news.bbc.co.uk/hi/english/sci/tech/newsid_2078000/2078507.stm
      Original Date: Wed, 3 Jul 2002 14:46:40 +0200 (CEST)

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      BBC NEWS
      Monday, 1 July, 2002, 14:55 GMT 15:55 UK

      Scientists estimate 30 billion Earths
      There could be billions of Earths out there

      By Dr David Whitehouse
      BBC News Online science editor

      Astronomers say there could be billions of Earths in our galaxy, the
      Milky Way.

      Their assessment comes after the discovery of the 100th exoplanet - a
      planet that circles a star other than our own.

      The latest find is a gas giant, just like all the other exoplanets so
      far detected, and orbits a Sun-like star 293 light-years away.

      Scientists say they are now in a position to try to estimate how many
      planets may exist in the galaxy and speculate on just how many could
      be like the Earth. The answer in both cases is billions.

      Virtually all the stars out to about 100 light-years distant have been
      surveyed. Of these 1,000 or so stars, about 10% have been found to
      possess planetary systems.

      So, with about 300 billion stars in our galaxy, there could be about
      30 billion planetary systems in the Milky Way alone; and a great many
      of these systems are very likely to include Earth-like worlds, say

      The 100th new planet circles the star HD 2039. It was found by
      astronomers using the Anglo-Australian Telescope as part of the
      Carnegie Institution Planet Search Program.

      The Jupiter-sized world circles its star every 1,210 days at a
      distance of about 320 million kilometres (200 million miles).

      Astronomer Dr Jean Schneider, who compiles the Extrasolar Planets
      Catalogue, told BBC News Online: "The 100th planet is symbolic and

      "The first discoveries concentrated on short orbital periods because
      of the limited timebase of observations. Now, we are learning more
      about the statistics of long orbital periods and know to what extent
      our own Jupiter is exceptional or not."

      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.

      Current planet detection technology - based on the "wobble" induced in
      the parent star by the gravitational pull of the orbiting planet - can
      only detect worlds about the mass of Saturn or larger. Earth-sized
      worlds are too small to be seen.

      But even in this "biased" survey of giants, the smaller worlds
      predominate - which makes astronomers think that Earth-like worlds do
      exist. They may even be as common as Jupiter-sized exoplanets.

      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

      Astronomers will have to wait for a new generation of space-based
      telescopes incorporating advanced detectors before they can detect
      Earth-sized worlds orbiting other stars.

      copyright bbc

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