美国太空总署(NASA)的科学家们在一颗编号为HD209458b的地外行星上发现有机元素。这
颗气体行星大小与木星类似，位於距离地球150光年以外的飞马星座。根据Hubble太空望
远镜和Spitzer太空望远镜的观测结果，HD209458b的大气层中存在水分子、二氧化碳分
子和甲烷分子。

http://chinese.wsj.com/big5/20091022/VID092514.asp?source=UpFeature

Basic Chemistry for Life Detected on Exoplanet HD 209458b
October 21, 2009

These are very exciting times for extrasolar planet hunters. Dozens of new
exoplanets have been discovered (some a little larger than Earth, others
several times the size of Jupiter) and astronomers are refining their already
sophisticated techniques to analyze the composition of the atmospheres of
these distant worlds.

Take exoplanet HD 209458b for example. It might not have the most romantic of
names (the designation "HD 209458" is the catalogue number of the Sun-like
star it's orbiting), but this exoplanet is famous in its own right. In 1999,
it was the first ever transiting exoplanet to be discovered. A transiting
exoplanet is a world that passes in front of its parent star when viewed from
Earth, blocking a little of the starlight for astronomers to detect and
measure.

By using the parent star's light to their advantage, NASA scientists have
been able to decipher what chemicals HD 209458b's atmosphere contains even
though it is 150 light years from Earth. This exoplanet is a very large gas
giant which has a very tight orbit around the star (it is therefore dubbed a
"Hot Jupiter"), so life isn't expected to be a possibility, but HD 209458b
contains the basic organic chemicals as used, and produced, by life as we
know it.

"It's the second planet outside our solar system in which water, methane and
carbon dioxide have been found, which are potentially important for
biological processes in habitable planets," said Mark Swain of NASA's Jet
Propulsion Laboratory. "Detecting organic compounds in two exoplanets now
raises the possibility that it will become commonplace to find planets with
molecules that may be tied to life."

Spectroscopic observations by the Hubble Space Telescope and the Spitzer
Space Telescope have been analysed and Swain has been able to deduce the
wavelengths of light that has been absorbed by HD 209458b's atmosphere. These
"absorption lines" provide the fingerprints of certain chemicals and it would
appear that water, methane and carbon dioxide are all present.

When compared with the first exoplanetary observations of organic chemicals
(exoplanet HD 189733b), the quantities of water and carbon dioxide appear to
be the same, however, HD 209458b contains more methane. Perhaps this is
indicative of some planetary formation process that might be particular to
this world. "It could mean there was something special about the formation of
this planet," Swain speculated.

Just because organic compounds are being found on distant worlds does not
mean life may or may not be present, it simply means that there are a lot
more life-giving chemicals around than we previously thought.

"...the detection of organic compounds will not necessarily mean there's life
on a planet, because there are other ways to generate such molecules," Swain
said. "If we detect organic chemicals on a rocky, Earth-like planet, we will
want to understand enough about the planet to rule out non-life processes
that could have led to those chemicals being there."

翻译：

因轨道接近HD 209458所以被□称「热木星」的气体行星HD 209458b，距离150光年，在
1999年因通过HD 209458时产生遮蔽被发现，依照「吸收光谱」分析大气层，比起另一个
发现水和二氧化碳的系外行星HD 189733b，还多了甲烷。系外行星目前只有这两个，被
探测到存在制造类地球生命的有机元素和水。

http://preview.tinyurl.com/yh925h5

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