An 'Astounding Time' for Planetary Discoveries|
By Marc Kaufman
Washington Post Staff Writer
Monday, March 24, 2008
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
"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
"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
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
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
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
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
Original article: Wahington Post
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