http://science.nasa.gov/headlines/y2009/04feb_greencomet.htm

Green Comet Approaches Earth
NASA Science news
02.04.2009

February 4, 2009: In 1996, a 7-year-old boy in China bent over the
eyepiece of a small telescope and saw something that would change his
life--a comet of flamboyant beauty, bright and puffy with an active
tail. At first he thought he himself had discovered it, but no, he
learned, two men named "Hale" and "Bopp" had beat him
to it. Mastering
his disappointment, young Quanzhi Ye resolved to find his own comet
one day.

And one day, he did.

Fast forward to a summer afternoon in July 2007. Ye, now 19 years old
and a student of meteorology at China's Sun Yat-sen University, bent
over his desk to stare at a black-and-white star field. The photo was
taken nights before by Taiwanese astronomer Chi Sheng Lin on "sky
patrol" at the Lulin Observatory. Ye's finger moved from point to
point--and stopped. One of the stars was not a star, it was a comet,
and
this time Ye saw it first.

Comet Lulin, named after the observatory in Taiwan where the
discovery-photo was taken, is now approaching Earth. "It is a green
beauty that could become visible to the naked eye any day now," says
Ye.

Amateur astronomer Jack Newton sends this photo from his backyard
observatory in Arizona:

http://science.nasa.gov/headlines/y2009/images/greencomet/Jack-Newton1.jpg

"My retired eyes still cannot see the brightening comet," says Newton,
"but my 14-inch telescope picked it up quite nicely on Feb. 1st."

The comet makes its closest approach to Earth (0.41 AU) on Feb. 24,
2009. Current estimates peg the maximum brightness at 4th or 5th
magnitude, which means dark country skies would be required to see it.
No one can say for sure, however, because this appears to be Lulin's
first visit to the inner solar system and its first exposure to
intense
sunlight. Surprises are possible.

Lulin's green color comes from the gases that make up its Jupiter-
sized
atmosphere. Jets spewing from the comet's nucleus contain cyanogen
(CN:
a poisonous gas found in many comets) and diatomic carbon (C2). Both
substances glow green when illuminated by sunlight in the near-vacuum
of
space.

In 1910, many people panicked when astronomers revealed Earth would
pass
through the cyanogen-rich tail of Comet Halley. False alarm: The wispy
tail of the comet couldn't penetrate Earth's dense atmosphere; even it
if had penetrated, there wasn't enough cyanogen to cause real trouble.
Comet Lulin will cause even less trouble than Halley did. At closest
approach in late February, Lulin will stop 38 million miles short of
Earth, utterly harmless.

To see Comet Lulin with your own eyes, set your alarm for 3 am. The
comet rises a few hours before the sun and may be found about 1/3rd of
the way up the southern sky before dawn. Here are some dates when it
is
especially easy to find:

sky map Feb. 6th:
Comet Lulin glides by Zubenelgenubi, a double star at the fulcrum of
Libra's scales. Zubenelgenubi is not only fun to say
(zuBEN-el-JA-newbee), but also a handy guide. You can see
Zubenelgenubi
with your unaided eye (it is about as bright as stars in the Big
Dipper); binoculars pointed at the binary star reveal Comet Lulin in
beautiful proximity. [sky map
]

Feb. 16th: Comet Lulin passes Spica in the constellation Virgo. Spica
is
a star of first magnitude and a guidepost even city astronomers cannot
miss. A finderscope pointed at Spica will capture Comet Lulin in the
field of view, centering the optics within a nudge of both objects.
[sky
map ]

Feb. 24th: Closest approach! On this special morning, Lulin will lie
just a few degrees from Saturn in the constellation Leo. Saturn is
obvious to the unaided eye, and Lulin could be as well. If this
doesn't
draw you out of bed, nothing will. [sky map
]

Ye notes that Comet Lulin is remarkable not only for its rare beauty,
but also for its rare manner of discovery. "This is a 'comet of
collaboration' between Taiwanese and Chinese astronomers," he says.
"The
discovery could not have been made without a contribution from both
sides of the Strait that separates our countries. Chi Sheng Lin and
other members of the Lulin Observatory staff enabled me to get the
images I wanted, while I analyzed the data and found the comet."

Somewhere this month, Ye imagines, another youngster will bend over an
eyepiece, see Comet Lulin, and feel the same thrill he did gazing at
Comet Hale-Bopp in 1996. And who knows where that might lead...?

"I hope that my experience might inspire other young people to pursue
the same starry dreams as myself," says Ye.
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