The Caldwell Objects

jets, like a stream of water from the nozzle of a
garden hose. The dense tips of the jets might be
material that the jets have plowed ahead of them
as they push[ed] forward. However, the models
also predict a high degree of gas turbulence,
which is not observed. Future improvements in
the observations and refinements in the models
will help us to understand the physics of the
outflows and the conditions of the jets."
The Saturn Nebula lies in the westernmost
reaches of Aquarius, a little more than 3° north of
the central Capricornus border. As mentioned
above, it is about 1¼° due west of Nu Aquarii,
which, in turn, is about 10° northwest of 3rdmagnitude
Delta (δ) Capricorni. The bright
nebula is easy to spot in 7x35 binoculars; it looks
like an 8th-magnitude star. Through the Genesis
at 23x the nebula is apparent (with averted
vision) as a slightly swollen star. Concentrate
long enough, and breathe rhythmically, and you
should see the planetary's outer envelope
materialize; look for a fuzzy, tightly wrapped
collar around the nebula's bright center.
Overall, the nebula appears round, and it
truly looks like a gaseous outer planet. Increasing
the magnification to 72x enhances the tight
inner ring and the pale green outer halo. (On the
subject of color: like me, Christian Luginbuhl
and Brian Skiff found the nebula pale green
when viewed through a 6-inch. But the colors of
planetaries are highly suggestive; most observers
see blue in NGC 7009.) At high power, the
central star appears as a bright point of light
centered in the densely packed inner ring. The
cavity is obvious, though it is not dark; the
central star looks like a candle seen through a
frost-covered window. Walter Scott Houston
called the central star "a beacon," but that was
after a cataract operation sensitized his observing
eye to ultraviolet light.
A very faint elliptical shell surrounds the
55
inner nebula, and it looks mottled. Perhaps this
mottling is what Angelo Secchi observed in the
19th century when he "saw [NGC 7009] sparkle,
and thought it a heap of stars." Unlike the case
with so many other planetaries, increased
magnification does not seem to greatly improve
views of NGC 7009, though it does bring out the
faint raylike extensions. Once spotted, these
gossamer wings can be seen at the limit of
resolution at 72x in the 4-inch. Burnham said that
the jets can be seen with a 10-inch under good
sea-level skies. Luginbuhl and Skiff clearly saw
"spike-like extensions" with a 10-inch, "each
seemingly as long as the disk." All these
observations are amazing if you consider that it
took a 72-inch telescope to discover the ansae.
Describing the view through a 12-inch telescope,
Luginbuhl and Skiff note that the core is
unevenly bright with "bright curds on the [north]
side and a darker area on the [east]." Here are the
scalloped edges already being resolved in a
modest amateur instrument. In a 17½-inch f/4.5
reflector, Barbara Wilson (who sees the nebula as
green at 32x) resolved the knots at the end of
each ansa at 154x. So here is a challenge for all
observers: how small a telescope will show these
knots? (Wilson also notes that the nebula's color
fades to a pale greenish-white at 154x.)
In August 1986 I had the opportunity to use
the 60-inch reflector atop Mount Wilson,
California. Observing with that venerable instrument
was like going back in time to the glory
days when astronomers began to peel away the
mysteries of the visible universe, like the skin of
an onion, with the depth of their questions and
the power of their telescopes. One of the first
objects I turned the 60-inch to was NGC 7009.
Photographs of this nebula, taken by the same
telescope, inspired me to look and wonder. Of
course, overexposed photographs from large
telescopes tend to exag-
The Caldwell Objects 221