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An 'Astounding Time' for Planetary Discoveries
Posted on Wednesday, March 26, 2008 (CDT) by Thoth
 It used to be that planets were familiar places such as Mars and Saturn that orbited our sun and were well known to all schoolchildren. Since astronomers identified the first planet outside our solar system 13 years ago, however, that idea has become downright quaint. Because now, according to the Extrasolar Planets Encyclopedia, there are 277 confirmed "extrasolar" planets, and quite a few more on the list of those suspected but not yet confirmed.
This explosion in planetary discoveries is taking place at such warp speed that even those most intimately involved are often amazed -- especially because their ultimate goal is nothing less than finding life elsewhere in the universe. "This is an absolutely astounding time for this field," said Mark Swain of NASA's Jet Propulsion Laboratory, who last week reported finding the first "exoplanet" to have organic methane in its atmosphere.
"We're not only finding them rapidly and in great variety, but we're starting to characterize them -- their mass and orbits, the properties of their atmospheres, measurements of day and night, dynamics of their winds," he said after the methane discovery was released last week.
So far, most
of the faraway planets are large, super-hot gas giants like Jupiter and
Saturn, which are not expected to be able to support life. They are
also so far away that humans are unlikely to ever directly observe
them. The planet with methane is a very close one -- it would take a
spaceship traveling at the speed of light 63 years to get there -- but
most others are hundreds or thousands of light-years away.
But with astronomers
regularly finding ingenious ways to locate and examine distant planets
-- sometimes with new technologies, sometimes because of inventive new
ways of analyzing data -- many in the field say it is just a matter of
time before they detect Earth-size, rocky planets elsewhere in the
cosmos.
"We've already been able to
detect planets with only five or 10 times the mass of the Earth," said
Sara Seager, a prominent extrasolar planet researcher and professor at
the Massachusetts Institute of Technology. The large gas giants
typically are hundreds of times more massive than our planet. "If the
technology improves a bit, with another push, we'll find Earths," she
said.
This is not to say that
scientists will necessarily find life on another distant planet --
although that is certainly the hope and, to some extent, the
expectation. But with the now-proven ability to detect molecules of
methane, a chemical often associated with life, researchers are
becoming more confident that they will be able to detect signs of
biological activity in faraway solar systems if it exists.
"Finding methane in the
atmosphere of a particular exoplanet is very important, but
demonstrating that we have the tools to identify molecules in these
atmospheres is of even greater significance," said Seager, who was not
involved in the study.
Carl B. Pilcher, director
of the NASA Astrobiology Institute at the Ames Research Center in
California, agrees that the big challenge now is to detect smaller,
Earth-size planets, then to find more and better ways to learn about
their atmospheres and other characteristics.
He said that just as the
exoplanet search has become supercharged of late, so, too, has the
search for life on other planets and in other solar systems, which is
the primary focus of the institute.
"There are a hundred
billion stars in our galaxy and probably a hundred billion other
galaxies with as many stars as ours, so it seems highly unlikely that
there are not Earth-like planets orbiting some of them out there,
waiting to be discovered," he said. "With that in mind, we're working
hard on techniques to answer the question of whether there's life on
them to be found."
Some of the work of finding
exoplanets and analyzing their orbits and atmospheres is being done
with ground-based telescopes, and some from orbiting observatories such
as the Hubble Space Telescope, which provided the data used to discover
exoplanet methane. In addition, astronomers and astrophysicists are
developing ever more powerful ways to interpret data and to use
spectroscopy, which splits light into its components to reveal the
"fingerprints" of various chemicals.
Considerably more powerful
hardware is also on the way. NASA's Kepler satellite, which is designed
to find distant planets as they transit in front of their stars, is
supposed to be launched next spring and is expected to locate hundreds
or thousands of new planets. The James Webb Space Telescope, a
high-powered Hubble successor that will be able to find atmospheric
molecules in rocky exoplanets rather than only in gas giants, is
scheduled for launch in 2013.
The recent discovery of
methane in the atmosphere of exoplanet HD 189733b was the kind of
breakthrough that the astrobiology institute and many others are
looking for -- even though the methane almost certainly has chemical
origins, as on Jupiter and Saturn, rather than biological ones. (The
planet is punishingly close to its sun -- making a full orbit in two
days -- and has an atmospheric temperature of about 1,700 degrees
Fahrenheit.) Nonetheless, methane can be a byproduct of biological
processes, and so learning how to detect it is essential.
The observations were made as the planet passed in front of its parent star in what astronomers call a transit.
As the light from the star
briefly pierced the atmosphere along the planet's edge, atmospheric
gases imprinted their identifiable signatures on the starlight.
The astronomers expected to
find signs of carbon monoxide on the spectrogram rather than methane,
and they were surprised by what they found.
"This indicates we don't really understand exoplanet atmospheres yet," Swain said.
But considering that 15
years ago not a single planet had been discovered outside our solar
system, Swain said, it is remarkable that scientists are now probing
the makeup and dynamics of planets so far away.
"I think the more we look,
the more evidence we'll find that the conditions are out there for life
to exist," he said. "I don't see a good reason why our situation in our
solar system should be unique. Perhaps uncommon, but not unique."
Copyright: The Washington Post
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