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William Steigerwald                      February 13, 2003
NASA Goddard Space Flight Center
(Phone: 301 286 5017)
William.A.Steigerwald{at}nasa.gov

RELEASE: 03-18

GRAB A FRONT-ROW SEAT FOR THE SUN-DANCING COMET

Jump on the internet for the chance to see a comet flirt with 
destruction as it passes close to the Sun February 18 by visiting the 
Solar and Heliospheric Observatory (SOHO) satellite at:

http://soho.nascom.nasa.gov/hotshots/2003_02_12/

It's dangerous to stare directly at the Sun, and the comet is too 
faint to be seen this way, anyway. In fact, only the most dedicated of 
sky watchers will have seen the comet "C/2002 V1 (NEAT)".  During 
January and so far this month, it hovered near the limits of naked-eye 
visibility in the evening sky and a viewer probably needed binoculars, 
pointed in exactly the right direction, to reveal anything at all.  
Alternatively, why not, sit back, relax, log onto the Internet and let 
the SOHO satellite do all the hard work?

SOHO is a European Space Agency/NASA spacecraft to study the Sun, from 
its interior to its outer atmosphere, and the solar wind. It 
constantly monitors solar activity and space weather events.  One 
instrument, the Large Angle and Spectrometric Coronagraph (LASCO), 
blots out the disc of the Sun, creating an artificial total eclipse. 
It then watches the tenuous outer atmosphere of the Sun for 
developments there.  As a bonus, LASCO has proved to be a spectacular 
comet-observing tool because of its combination of high sensitivity 
and large field of view, among other factors.

The previous comet to pass through the SOHO field of view, "C/2002 
X5", made its journey during the last week of January.  At that time, 
the SOHO web site, which displays real time images from the 
spacecraft, recorded seven million requests to see the comet images.

Now, armchair observers all around the world have a chance to view 
another comet and, this particular time, the stakes are higher as the 
comet might not survive its close pass of the Sun.

Comets are lumps of frozen gas and water, laced with dust, from cold, 
distant regions of the solar system, beyond the planet Neptune. They 
range in size from boulders to mountains and even larger. Astronomers 
believe comets are relics from the solar nebula, a cloud of gas and 
dust which evolved to form the solar system. As the comets formed, 
dust from the nebula was incorporated into the ices that comprise a 
comet. Occasionally, a slight gravitational disturbance from another 
solar system object or a nearby star will send a comet tumbling into 
the inner solar system, where solar heat and light vaporizes gas and 
liberates dust from the comet's surface, giving the comet its 
characteristic tail.

Comets are discovered all the time.  When they are seen first by 
individual observers, they are named after the discoverer. 
Increasingly though these days, comets are first seen by automated 
telescope patrols, designed to scan the skies looking for objects that 
could pass close to Earth.  These discoveries are given catalogue 
references.

Comet C/2002 V1 (NEAT) was discovered by NASA's Near Earth Asteroid 
Tracking program, run by the Jet Propulsion Laboratory (JPL), 
Pasadena, Calif., on 6 November 2002.  At that time it was 25,000 
times fainter than the human eye can perceive.  Since that time, 
astronomers have been tracking it carefully.  Initially, the comet 
brightened so much that astronomers wondered whether it would become 
bright enough to be seen during the day, as it rounded the Sun!

However, during January, the comet failed to brighten as hoped.  Now, 
it is expected to disappear from view to Earth-bound observers 
sometime around 11 February 2003, as it heads towards the Sun for its 
closest approach on 18 February.  It will not be lost from all sight, 
however, as in space, SOHO will be watching.  C/2002 V1 (NEAT) is 
expected to pass into the LASCO instrument's field of view early on 16 
February and stay there until 20 February.

There is even a small possibility that something rare and dramatic 
will occur: the comet may not survive its encounter. Comet C/2002 V1 
(NEAT) will pass the Sun at less than a tenth of the distance between 
the Earth and the Sun and could be pulled to pieces by the Sun's 
gravitational field.  "If it happens, it would be the 'frosting on the 
cake'.  If not, the fly-by itself should be impressive enough," says 
Dr. Bernhard Fleck, the SOHO Project Scientist for ESA.

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