This artist's illustration gives an
impression of how common planets are around the stars in the Milky Way. The
planets, their orbits and their host stars are all vastly magnified compared to
their real separations. A six-year search that surveyed millions of stars using
the microlensing technique concluded that planets around stars are the rule
rather than the exception. The average number of planets per star is greater
than one. This means that there is likely to be a minimum of 1,500 planets
within just 50 light-years of Earth.
The results are based on observations
taken over six years by the PLANET (Probing Lensing Anomalies NETwork)
collaboration, which was founded in 1995. The study concludes that there are
far more Earth-sized planets than bloated Jupiter-sized worlds. This is based
on calibrating a planetary mass function that shows the number of planets
increases for lower mass worlds. A rough estimate from this survey would point
to the existence of more than 10 billion terrestrial planets across our galaxy.
The results were published in the Jan.
12, 2012, issue of the British science journal Nature.
Image Credit: NASA, ESA, and M. Kornmesser
(ESO)
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