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The ring nebula is probably one of the most famous deep sky objects
in the sky. Generally when amatuers begin their telescopic journey, after
the Orion Nebula
, the Ring is one of the next objects on the list. Even through a small
telescope its bright and distinctive shape sets it apart from a typical
field of stars. An image such as this, when acquired using a CCD camera,
shows both the detail and color of this remarkable object. Like
others
of its type, the Ring Nebula is the expelled outer envelope of a once
aged star that has now reached its final stages of life. This bubble of
gas is more than 2,000 light years away and therefore is itself more than
1 light year in diameter. The white dwarf (central star which is the
naked core of the original sunlike whole) is extremely hot (100,000K) and
emits copious amounts of UV radiation. This emission excites various
gases in the bubble and makes them glow (not unlike a neon light). The
sphere of gas continues to expand; and if we could watch for the next
300,000 years the bubble would thin and disintegrate leaving the cold dark
husk of the cooled white dwarf.
Technically a better description of this "bubble" of gas is something a
bit more cylindrical. In this case we are looking down the major axis (shaft)
of the short tube. Previous episodes of mass loss can be seen in concentric
layers far from the brightest portion. The bottom image attempts to display
these features. Please visit the
NOAO M57 to
see a similar picture created with a larger telescope. If we were able
to look at the ring nebula from the side (rotate 90 degrees), it would look
like M76. Also note the galaxy, IC 1296,
which floats majestically in the background.
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