BBC News Science & Environment
10 January 2011 Last updated at 23:01 GMT
Rocky exoplanet milestone in hunt for Earth-like worlds
Kepler 10b Kepler 10b is 560 light-years from Earth
Astronomers have discovered the smallest planet outside our solar system, and
the first that is undoubtedly rocky like Earth.
Measurements of unprecedented precision have shown that the planet, Kepler 10b,
has a diameter slightly lower than Earth's, and a mass 4.6 times higher.
However, because it orbits its host star so closely, the planet could not
harbour life.
The discovery has been hailed as "among the most profound in human history".
The result was announced at the 217th annual meeting of the American
Astronomical Society in Seattle, US, by Nasa's Kepler team.
The Kepler space telescope, designed to look for the signs of far-flung
planets, first spotted the planet 560 light-years away, alongside hundreds of
other candidate planets.
Kepler relies on the "transiting" technique, which looks for planets that pass
between their host star and the Earth.
A tiny fraction of the star's light is blocked periodically, giving a hint that
the star has a planet orbiting it.
The radius of the planet correlates to exactly how much light is blocked when
it passes.
Continue reading the main story
"Start Quote
This report... will be marked as among the most profound scientific
discoveries in human history"
End Quote Geoffrey Marcy University of California Berkeley
Follow-up measurements by a telescope at the Keck observatory in Hawaii
confirmed the find of Kepler 10b by measuring how the planet pulls to and fro
on its parent star as it orbits.
Ever-expanding fields
This cosmic dance causes tiny changes in the colour of the starlight that is
measured by telescopes.
However, what completed the suite of measurements for the Kepler team was the
use of asteroseismology - a study of distant stars that is akin to the study of
earthquakes on the Earth.
The oscillations that occur within a star - as within the Earth - affect the
frequencies of the light that the star emits in a telltale sign of the star's
size.
With the size of the host star, the details of the planet's and star's mutual
dance, and the planet's radius, the density of the planet can be calculated.
"All of our very best capabilities have converged on this one result and they
all converge to form a picture of this planet," said Natalie Batalha, a San
Jose State University professor of astrophysics who helps lead the Kepler
science mission for Nasa.
She told BBC News that the result is unique in an ever-expanding field of
exoplanet discoveries, with smaller and smaller exoplanets discovered as
experimental methods improve.
"We're always pushing down toward smaller and less massive, so it's natural
that we're arriving there," she said.
"But perhaps what's not so natural is that we've pinned down the properties of
this planet with such fantastic accuracy that we're able to say without a doubt
that this is a rocky world, something that you could actually stand on."
Alone or not?
One could, if it were not so close to its host star that it's daytime
temperature exceeds 1300C - so Kepler 10b is not a sensible candidate to host
life. However, as Professor Batalha explained, it is a significant step in
Kepler's mission.
"We want to know if we're alone in the galaxy, simply put - and this is one
link in the chain toward getting to that objective.
"First we need to know if planets that could potentially harbour life are
common, and we don't know if that's true - that's what Kepler is aiming to do."
Pioneer of the hunt for exoplanets Geoffrey Marcy, from the University of
California Berkeley, said that Kepler 10b represented "a planetary missing
link, a bridge between the gas giant planets we've been finding and the Earth
itself, a transition... between what we've been finding and what we're hoping
to find".
"This report... will be marked as among the most profound scientific
discoveries in human history," he said.
------------------------------------
Post message: [email protected]
Subscribe : [email protected]
Unsubscribe : [email protected]
List owner : [email protected]
Homepage : http://proletar.8m.com/Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/proletar/
<*> Your email settings:
Individual Email | Traditional
<*> To change settings online go to:
http://groups.yahoo.com/group/proletar/join
(Yahoo! ID required)
<*> To change settings via email:
[email protected]
[email protected]
<*> To unsubscribe from this group, send an email to:
[email protected]
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
