"Intelligent Life May be Young in the Universe"
- URL to a fascinating post in the Daily Galaxy
So, there may be a reason why we seem to be alone in the universe
(Madness takes its toll. Please have exact change)
"Building a terrestrial planet requires raw materials that weren't
available in the early history of the universe. The Big Bang filled space with
hydrogen and helium. Chemical elements like silicon and oxygen - key components
of rocks - had to be cooked up over time by stars. But how long did that
take? How many of such heavy elements do you need to form planets?
Studies have shown that Jupiter-sized gas giants tend to form around stars
containing more heavy elements than the Sun. However, research by a team
of astronomers completed last year found that planets smaller than Neptune
are located around a wide variety of stars, including those with fewer heavy
elements than the Sun. As a result, rocky worlds like Earth could have
formed earlier than expected in the universe's history.
"This work suggests that terrestrial worlds could form at almost any time
in our galaxy's history," said Smithsonian astronomer David Latham
(_Harvard-Smithsonian Center for Astrophysics_
Smithsonian%20Center%20for%20Astrophysics)&t=h) ). "You don't need many earlier generations of
stars." Latham played a lead role in the study, which was led by Lars A.
Buchhave from the University of Copenhagen published in the journal Nature.
Astronomers call chemical elements heavier than hydrogen and helium
"metals." They measure the metal content, or metallicities, of other stars using
the Sun as a benchmark. Stars with more heavy elements are considered
metal-rich while stars with fewer heavy elements are considered metal-poor.
Latham and his colleagues examined more than 150 stars known to have
planets, based on data from NASA's _Kepler spacecraft_ (http://kepler.nasa.gov/)
. They measured the stars' metallicities and correlated that with the sizes
of the associated planets. Large planets tended to orbit stars with solar
metallicities or higher. Smaller worlds, though, were found around
metal-rich and metal-poor stars alike.* "Giant planets prefer metal-rich stars.
Little ones don't," explained Latham.
They found that terrestrial planets form at a wide range of metallicities,
including systems with only one-quarter of the Sun's metal content.
Their discovery supports the "core accretion" model of planet formation. In
this model, primordial dust accumulates into mile-sized planetesimals that
then coalesce into full-fledged planets. The largest, weighing 10 times
Earth, can then gather surrounding hydrogen and become a gas giant.
A gas giant's core must form quickly since hydrogen in the protoplanetary
disk dissipates rapidly, swept away by stellar winds in just a few million
years. Higher metallicities might support the formation of large cores,
explaining why we're more likely to find a gas giant orbiting a metal-rich
star."This result fits with the core accretion model of planet formation in a
natural way," said Latham.
Although there may be exo planets billions of years older than Earth,
Harvard's _Dimitar Sasselov_ (http://en.wikipedia.org/wiki/Dimitar_Sasselov)
believes that intelligent life may be in it's "very young" stage in the
_observable Universe_ (http://en.wikipedia.org/wiki/Observable_universe) . Its
200 billion galaxies show a clear potential to continue on as we see them
today for hundreds of billions of years, if not much longer. Because planets
and life are so young in our Universe, says Sasselov, perhaps "the human
species are not late comers to the party. We may be among the early ones."
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