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EMBARGOED UNTIL: April 15, 1996

PHOTO NO.: STScI-PRC96-13b


COMETARY KNOTS AROUND A DYING STAR

These gigantic, tadpole-shaped objects are probably the result
of a dying star's last gasps. Dubbed "cometary knots" because
their glowing heads and gossamer tails resemble comets, the
gaseous objects probably were formed during a star's final
stages of life.

Hubble astronomer C. Robert O'Dell and graduate student
Kerry P. Handron of Rice University in Houston, Texas discovered
thousands of these knots with the Hubble Space Telescope while
exploring the Helix nebula, the closest planetary nebula to Earth at
450 light-years away in the constellation Aquarius. Although
ground-based telescopes have revealed such objects, astronomers
have never seen so many of them. The most visible knots all lie
along the inner edge of the doomed star's ring, trillions of miles
away from the star's nucleus. Although these gaseous knots
appear small, they're actually huge. Each gaseous head is at
least twice the size of our solar system; each tail stretches for
100 billion miles, about 1,000 times the distance between the
Earth and the Sun. Astronomers theorize that the doomed star
spews hot, lower-density gas from its surface, which collides with
cooler, higher-density gas that had been ejected 10,000 years before.
The crash fragments the smooth cloud surrounding the star into
smaller, denser finger-like droplets, like dripping paint.

This image was taken in August, 1994 with Hubble's Wide Field
Planetary Camera 2. The red light depicts nitrogen emission
([NII] 6584A); green, hydrogen (H-alpha, 6563A); and blue,
oxygen (5007A).

Credit: Robert O'Dell, Kerry P. Handron (Rice University,
Houston, Texas) and NASA

Image files in GIF and JPEG format and captions may be accessed
on Internet via anonymous ftp from oposite.stsci.edu in /pubinfo.

GIF JPEG
PRC96-13b Helix Nebula gif/HelixD.gif jpeg/HelixD.jpg

Higher resolution digital versions (300dpi JPEG) of the release
photographs will be available temporarily in /pubinfo/hrtemp:
96-13b.jpg (color) and 96-13bBW.jpg (black/white).

GIF and JPEG images, captions and press release text are available
via World Wide Web at http://www.stsci.edu/pubinfo/PR/96/13.html
and via links in http://www.stsci.edu/pubinfo/Latest.html or
http://www.stsci.edu/pubinfo/Pictures.html.