The Caldwell Objects

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resides within two larger lobes of gas blown off
the star during an earlier ejection phase. These
outer lobes are "pinched" by a clumpy ring of
dense gas that presumably was ejected along the
orbital plane of the central binary star. The HST
images (one of which is reproduced to the
lower right) also reveal
jets of gas shooting out of
opposite ends of the
nebula at right angles to
the equatorial ring.
Those jets are fleeing the
region at speeds of 25 km
per second or more,
colliding with the gas
ahead of them and
creating the bright arcs
visible near the outer
edges of the lobes. The
jets themselves may be
wobbling and turning on
and off episodically,
adding further
complexity to these
interpretations.
At the June 2000
meeting of the American Astronomical Society,
Bruce Balick (University of Washington)
described how he and graduate student Darren
Reed had analyzed HST images of the nebula
and noticed a series of very faint features surrounding
it. These wisps, they realized, were a
series of at least nine rings ejected earlier at
regular 1,500-year intervals. Apparently the star
puffed these rings out as part of its preparations
for death. Each puff contains thousands of Earth
masses of stellar material. "Each outburst would
have been a spectacular sight from any nearby
planet," Balick said. "The star would have
swelled to about the size of the Earth's orbit." The
excitement offered by HST's images of the Cat's
Eye should help you
imagine the ongoing chaos of that system as you
squint at the nebula's delicate glow through your
telescope. That is the beauty of being an amateur
in the 21st century: we are more knowledgeable
than ever about the "mystery" clouds that have
haunted astronomers for centuries.
34 Deep-Sky Companions: The Caldwell Objects