The Caldwell Objects

other popular nickname, the Eight-Burst Nebula.
Astronomers interpret the various forms of
planetary nebulae as being different
manifestations of one three-dimensional model.
In that model, gas flows from a central star and
funnels out at right angles to a denser torus of
material girdling the star. Ring nebulae like M57
and NGC 3132 manifest themselves when we
happen to look down the gas-flow axis. The
outer, cooler halos are remnants of the slow wind
cast off by the hot central star when it was still a
red giant. If we could see ring nebulae from the
side, they would probably look much like the
planetary nebula M76 in Perseus.
High-resolution images from Hubble also
reveal the Eight-Burst features as well as several
new ones, including a wide pillar along
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the nebula's major axis. These features are visible
in the light of thrice-ionized oxygen (Ο III) and
hydrogen-alpha. The hydrogen-alpha images
also show a thin equatorial band of material
girdling the main nebula around its waist, and a
fine, jetlike feature extending radially from the
girdle. The girdle is made of carbon-rich dust
particles that have condensed out of the
expanding gases. Astronomers believe that in the
distant future the dust could contribute to the
formation of new stars and planets. The HST
image of all this ethereal splendor sets the
imagination free; it's as if we're peering at the Sun
(the central star) through a rusted porthole (the
ring) of a ship in the shallows (the hot vapors in
the center of the ring).
If we accept a distance of 2,000 light-years
for NGC 3132, the planetary's true dimensions
The Caldwell Objects 293