NASA and other space agencies have
launched several missions to search for exoplanets, planets that orbit other
stars. The Holy Grail of such programs is finding an Earth-like planet orbiting
a sun-like star at the right distance to allow liquid water on the surface.
Such planets seem to be the most likely candidates to search for life.
While astronomers have yet to find
a perfect Earth 2, statistical analysis of NASA’s most successful planet
hunter, the Kepler Mission, uncovered some promising data. A study by NASA
scientists alongside collaborators from around the world who worked on the
Kepler mission came to an exciting conclusion. According to the research, about
half the stars similar in temperature to our Sun could have a rocky planet
capable of supporting liquid water on its surface.
Image Caption/Credit: NASA’s Kepler Planet Finder telescope,
credit NASA
"Kepler already told us there
were billions of planets, but now we know a good chunk of those planets might
be rocky and habitable," said the lead author Steve Bryson, a researcher
at NASA's Ames Research. "Though this result is far from a final value,
and water on a planet's surface is only one of many factors to support life,
it's extremely exciting that we calculated these worlds are this common with
such high confidence and precision."
Kepler detected planets by continuously
staring at thousands of stars, watching for a tell-tale drop in brightness
caused by an orbiting planet crossing in front of a star. Such a method
couldn’t detect planetary systems seen more face on, so astronomers had to use
statistical methods to extrapolate from the Kepler data to all the other stars
in our galaxy. Kepler discovered so many exoplanets from its limited mission
that astronomers now believe that more than half of the four billion stars in
the Milky planet possess planets, typically more than one.
Using their most conservative
estimate, that 7% of all sun-like stars have Earth-like planets, meaning some
300 million exist in our Milky Way alone. Their most likely estimate states
that Earth-like planets orbit 50% of sun-like stars, making more than 2 billion
Earth-like planets. Since we know of only one planet with life, ours, those
planets are the best place to begin to search for alien forms of life.
Each month, I write an
astronomy-related column piece for the Oklahoman newspaper. On the following
day, I post that same column to my blog page.
