Astronomers estimate 17 billion Earth-like planets in the Milky Way

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BBC: At the 221st American Astronomical Society meeting, Christopher Burke of the Seti Institute announced that the number of planet candidates the Kepler space telescope had identified had reached 2740. Since 2009 Kepler has observed more than 150 000 stars in the same area of space. François Fressin of the Harvard–Smithsonian Center for Astrophysics and his colleagues have been examining the stars for minute dips in brightness that may be caused when a planet passes in front of one. By ruling out other possibilities, and by calculating the masses of the planets, Fressin’s team has determined that 17% of the stars have planets up to 1.25 times the size of Earth that have orbits of less than 85 days. That means that there may be more than 17 billion Earth-sized planets in the Milky Way.

3 thoughts on “Astronomers estimate 17 billion Earth-like planets in the Milky Way”

  1. The headline and conclusion are highly suspect. Did the astronomers say 17 billion, or was this the PT writer/editor calculation? There may be 100 billion (or more) stars in the Milky Way, but how many of those stars are in environments similar to the Kepler field of view? How many Milky way stars are mainstream stars, old enough (>3 billion years) to have an earth-like environment. Reference the Kepler Cluster Study at:
    http://kepler.nasa.gov/files/mws/audio/lectures/2011/2011May23AAS/Meibom/
    PT Editors; please filter these exaggerated and unsupported claims, or give a reference to justify them.

  3. What is so exaggerated here? The term ‘earth like’ is not well defined, here it only means a terrestial planet of roughly the size of earth.
    Only if ‘earth like’ is interpreted (arbitrarily) narrowly incl. same chemistry, geology, age, evolution, biology … (should the inhabitants speak english, too, as in some science fiction films?), then ‘earth like’ becomes also correspondingly unlikely.
    I think the message from recent findings is, that at least the very rough factors for finding anything comparable to earth have been found to be far more likely than assumed years ago. For stars to have planets is rather the norm than an exception. Even multiple star systems seem to harbour planet systems surprisingly often. Planetary systems are obviously quite diverse, but terrestrial planets become visible as normal part of these. And still the view on the distribution of structures of planetary systems only starts to become clearer due to strong bias of existing detection possibilities in favor of big planets and/or planets near to the star.
    For judging the probability of finding an evolved biosphere (how alien it may be) of course then more factors will have to be investigated, a relatively simple one being the age of the star.