Shadow Of A Comet
Explanation:
Hale-Bopp,
the Great Comet of 1997, may have been
the most viewed comet in history -
visible even from bright metropolitan skies.
Astronomers are now reporting that this
magnificent comet also cast a
shadow against the glare of the solar system's ultraviolet haze.
This false-color image represents a slice of the sky viewed by the
SWAN (Solar Wind ANisotropy) instrument aboard the space-based
SOHO observatory.
Recorded on March 8, 1997 it shows a
general haze of solar ultraviolet light
scattered by interstellar hydrogen.
The sun itself is positioned below the bottom center of the
cropped image and the large bright spot is
ultraviolet sunlight scattered by
the cloud of hydrogen gas surrounding Hale-Bopp's nucleus.
Just above and to the left is a broad, diffuse, dark
streak - the 150 million kilometer long shadow
produced by
the denser regions of this hydrogen envelope.
Why are comets surrounded
by hydrogen?
The hydrogen comes from
the breakup of water (H20) vapor released as the
comet nucleus approaches the sun.
These observations indicate that Hale-Bopp's
nucleus
was producing about 300 tons of water per second.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings,
and Disclaimers
NASA Official: Jay Norris.
Specific
rights apply.
A service of:
LHEA at
NASA /
GSFC
& Michigan Tech. U.
