The Caldwell Objects

43 & 44
to be made of individual stars when scrutinized
with his powerful reflectors. William Herschel
concluded that his observations vindicated
Immanuel Kant, who in 1775 had convinced
himself that the small, elliptical, luminous
patches then called "nebulous stars" were actually
other "universes" beyond the Milky Way. William
gained further conviction when he turned his
telescope to numerous "nebulae" and resolved
them into clusters of stars. He came to believe
that all extended objects were distant stellar
systems that could be resolved with large enough
telescopes. Even his discovery, in 1785, that the
Ring Nebula in Lyra was "perforated" didn't
dissuade Herschel from his belief, for he still
managed to spot stars within the luminous body
of the Ring — or so he thought. Later discoveries
would make Herschel reconsider his theory. But
his ideas didn't go unnoticed, for, as we can see,
Smyth's vivid interpretation of NGC 7479's
structure was clearly an extension of Herschel's
thinking.
We are lucky to have today's superior telescopes
and lenses, for even at 72x the 4-inch
Genesis reveals fine structure in NGC 7479. The
galaxy's tiny core, for instance, becomes
apparent, as does its bar, which has a needle-
178
like quality. Spiral structure is near the limit of
visibility at higher powers, as are some knots
embedded in the galaxy's arms. Owners of
monster Dobsonian telescopes can have a field
day with this galaxy. In a 1997 Astrophysical
Journal Supplement Series paper, Rosa M.
Gonzalez Delgado (Space Telescope Science
Institute) and her colleagues reported the discovery
of 86 Η II regions in the galaxy's two main
spiral arms. The galaxy is literally bursting with
star formation.
Supernova hunters should be on the lookout
for new stars in this active galaxy. On July 27,
1990, the Berkeley Automated Supernova Search
project discovered a roughly 16th-mag-nitude
supernova (SN 1990U) lying on a possible ΗII
region 22" west and 54" south of the galaxy's
nucleus. The new star was a Type Ic supernova,
one that fades slowly, dimming by about 3
magnitudes during the first 150 days after
maximum light. Since the spectra of Type Ic
supernovae show no obvious hydrogen or
helium lines, they presumably occur when
massive stars self-destruct after ejecting their
outer envelopes of hydrogen and helium.
Studying these events helps astronomers better
understand how stars explode.
Deep-Sky Companions: The Caldwell Objects