The Caldwell Objects

years. A total of 43 star-cluster candidates have
also been located, of which 18 are probable open
star clusters. (IC 1613 contains no bright globular
clusters.) Hubble Space Telescope observations of
roughly 700 square light-years in the galaxy's
core support the notion that IC 1613 is still
birthing stars. For the past 250 to 350 million
years, the galaxy has had a roughly constant starformation
rate of about 35,000 suns per year,
which is about 50 percent lower than it was 400
to 900 million years ago.
The galaxy is also rich in supergiant stars,
and spectroscopic observations with the William
Herschel Telescope on La Palma in the Canary
Islands have revealed six interlocking interstellar
shells in IC 1613. The shells are gigantic, with
diameters ranging from 220 to 1,000 light-years,
and they are expanding at speeds up to 50 km
per second. Stellar winds associated with
supernova explosions seem to drive this
expansion. The region could be the first stage in
the formation of a supergiant
The Caldwell Objects
51
shell with a diameter greater than 3,000 lightyears.
Others have found that expanding "superbubbles"
cover the whole of the galaxy. Each
superbubble contains at least one stellar association,
and the more massive stars in these associations
seem to be quite important in shaping
the interstellar medium of the galaxy.
HST also imaged Cepheid variable stars in
IC 1613, and those stars confirmed R. Brent
Tully's distance determination of 2.3 million
light-years, which was derived by more indirect
means.
Finding the field containing IC 1613 is not
hard, but seeing the galaxy is another thing. Start
by finding the 4th-magnitude stars Epsilon (ε)
and Delta (δ) Piscium in the southernmost Fish's
cord. The center of a tight equilateral triangle of
roughly 6th-magnitude stars — 73, 77, and 80
Piscium — lies just 2½° south-southeast of
Epsilon Piscium. Confirm the presence of these
stars with binoculars. A curved line of three stars
(magnitudes 6.3, 8.0, and 7.2, respectively)
trickles 2½° south of 77 Piscium, bending ever so
slightly east, then west, in the process. IC 1613 is
immediately south of the third and southernmost
(7th-magnitude) star, which places it inside of
another 1°-wide triangle comprising the justmentioned
7th-mag-nitude star and two 6thmagnitude
stars (29 and 26 Ceti). Be certain you
have the right field, because 29 and 26 Ceti are
part of a northeast-southwest trending line of
stars. For those who own an equatorial mount, IC
1613 is 3½° due south of 73 Piscium in the first
triangle. All these stars are visible in the finder
chart on page 206.
I tried unsuccessfully to see IC 1613 on
several nights in 1997. How utterly absurd, I
thought, that Patrick Caldwell-Moore would
have selected such an object for his catalog. How
did he expect anyone to see such a hideously dim
galaxy? I knew of no guide that
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