NASA'S KEPLER MISSION DISCOVERS ITS
FIRST ROCKY PLANET
From NASA
Jan. 10, 2011
The discovery of this
so-called exoplanet is based on more than eight months of data collected by the
spacecraft from May 2009 to early January 2010. "All of Kepler's best
capabilities have converged to yield the first solid evidence of a rocky planet
orbiting a star other than our sun," said Natalie Batalha, Kepler's deputy
science team lead at NASA's Ames Research Center
in Moffett Field , Calif. , and primary author of a paper on the
discovery accepted by the Astrophysical Journal. "The Kepler team made a
commitment in 2010 about finding the telltale signatures of small planets in
the data, and it's beginning to pay off."
Kepler's ultra-precise
photometer measures the tiny decrease in a star's brightness that occurs when a
planet crosses in front of it. The size of the planet can
be derived from these periodic dips in brightness. The distance between the
planet and the star is calculated by measuring the time between successive dips
as the planet orbits the star. Kepler is the first NASA mission capable of
finding Earth-size planets in or near the habitable zone, the region in a
planetary system where liquid water can exist on the planet's surface. However,
since it orbits once every 0.84 days, Kepler-10b is more than 20 times closer
to its star than Mercury is to our sun and not in the habitable zone.
Kepler-10 was the first star
identified that could potentially harbor a small transiting planet, placing it
at the top of the list for ground-based observations with the W.M. Keck
Observatory 10-meter telescope in Hawaii .
Scientists waiting for a signal to confirm Kepler-10b as a planet were not
disappointed. Keck was able to measure tiny changes in the star's spectrum,
called Doppler shifts, caused by the telltale tug exerted by the orbiting
planet on the star.
"The discovery of
Kepler 10-b is a significant milestone in the search for planets similar to our
own," said Douglas Hudgins, Kepler program scientist at NASA Headquarters
in Washington .
"Although this planet is not in the habitable zone, the exciting find
showcases the kinds of discoveries made possible by the mission and the promise
of many more to come," he said. Knowledge of the planet is only as good as
the knowledge of the star it orbits. Because Kepler-10 is one of the brighter
stars being targeted by Kepler, scientists were able to detect high frequency
variations in the star's brightness generated by stellar oscillations, or
starquakes. This analysis allowed scientists to pin down Kepler-10b's properties.
There is a clear signal in
the data arising from light waves that travel within the interior of the star.
Kepler Asteroseismic Science Consortium scientists use the information to
better understand the star, just as earthquakes are used to learn about Earth's
interior structure. As a result of this analysis, Kepler-10 is one of the most
well characterized planet-hosting stars in the universe. That's good news for
the team studying Kepler-10b. Accurate stellar properties yield accurate planet
properties. In the case of Kepler-10b, the picture that emerges is of a rocky
planet with a mass 4.6 times that of Earth and with an average density of 8.8
grams per cubic centimeter -- similar to that of an iron dumbbell.
[Just in case you missed the
original announcement! Of course the discovery of rocky planets like Earth is a
big step towards finding life elsewhere in our Galaxy. If these planets are as
common as they appear to be I think the odds of finding life – even complex
life – are pretty good. What we have is still pretty circumstantial but as more
evidence accumulates of the possibility of life elsewhere – especially in
environments not that dissimilar to those here – that possibility must be
moving in the direction of certainty. Now all we need to do is determine which
of the present candidates are the most likely to harbour life and send probes
to have a look – no matter how long that would take.]
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