The Ring Nebula is one
of the most famous objects in the sky and perhaps the most spectacular
example of a planetary nebula. It is bright, relatively large and
most important of all, easy to find midway between two bright stars in
in a 90mm ETX at 50x with a Meade Super Wide Angle 24.5mm eyepiece.
The field of view (circle) is 79'. The two bright stars are Sulafat
(Gamma, 14 Lyr) and Sheliak (Beta, 10 Lyr). Note how the position
of M57 midway between these stars makes it very easy to find.
The Ring is visible in a
3-inch telescope as an elongated hazy spot. A 6-inch scope will reveal
the famous smoke ring structure. Many observers describe M57 as having
a slight greenish tint. Users of larger telescopes should try to
see the faint central star. The magnitude of this star is uncertain
(perhaps as faint as 14.7 magnitude) and may be variable. There is
some question concerning how large an aperture is required to see it.
Due to the surrounding nebulosity it may be more difficult to see than
another star of similar magnitude. A 14 inch may be required for
most observers on a typical night. I've seen it in my 18 inch with
little trouble. Another difficult but rewarding observation is to
see the structure in the fainter central nebula. With a 16-inch or
larger scope look for streaks or streamers.
At the end of an observing
session I often like to look up a few old friends such as M57. After
years of observing these favorites no chart is needed to find them.
I am always struck by the combination of size and brightness in the Ring,
particularly after spending the evening hunting down other tiny, faint
examples of planetary nebulae. The Ring may not be the largest planetary.
It's not even the brightest. But it is without question best.
The above image
is from the Hubble Space Telescope. The vivid colors are not visible
in the eyepiece at all. In the photograph they provide an indication
of the different types of gases and conditions throughout the nebula.
In the Hubble Space Telescope
image blue traces very hot helium gas. Green represents hot oxygen
and red indicates relatively cooler nitrogen. It first appeared that
we were viewing M57 as an irregular, spherical bubble in space about the
faint central star. The bright edges which form the apparent ring
were explained as the result of looking through more glowing material at
the edges of the shell. Some researchers pointed out as early as 1960 that
this might not be the case because the difference of brightness between
the inner nebula and outer ring was too great. In recent years evidence
has accumulated that the real shape of the Ring nebula may be a cylinder
and we are viewing it from one end. If viewed from another direction
it would probably look very different, perhaps more like the Little Dumbbell
nebula (M76). Note the dark spots that are made by small, dark clouds
superimposed on the glowing gas. Few of these clouds are found in
the middle of the nebula, suggesting that the overall structure is truly