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NGC 6369 in
V and I filters
[Image Courtesy of NASA and H. Bond (STScI)]
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NASA's
Hubble Space Telescope has caught a glimpse
of a cosmic ghost, the glowing remains
of a dying star called NGC 6369. The glowing
apparition is known to amateur astronomers
as the "Little Ghost Nebula,"
because it appears as a small, ghostly
cloud surrounding the faint, dying central
star.
When a star
with a mass similar to that of our own
Sun nears the end of its lifetime, it
expands in size to become a red giant.
The red-giant stage ends when the star
expels its outer layers into space, producing
a faintly glowing nebula. Many of the
details of ejection process are not visible
from ground-based telescopes because of
the blurring produced by the Earth's atmosphere.
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The
remnant stellar core in the center sends
out a flood of ultraviolet light into the
surrounding gas. At larger distances from
the star, one can see fainter wisps of gas
that were lost from the star at the beginning
of the ejection process.
Our own Sun may eject a
similar nebula, but not for another 5 billion
years. The gas will expand away from the
star at about 15 miles per second, dissipating
into interstellar space after some 10,000
years. After that, the remnant stellar ember
in the center will gradually cool off for
billions of years as a tiny white dwarf
star, and eventually wink out. |
NGC 6369 in the F658N ([N
II]) filter |
