The Caldwell Objects

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NGC 4236
Type: Barred Spiral Galaxy
(SBdm)
Con: Draco
RA: 12 h 16.7 m
Dec: +69° 27.8'
Mag: 9.6
Dim: 19.6' x 7.6'
SB: 15.0
Dist: 7 million light-years Disc: William
Herschel, 1793
W. H ERSCHEL: [Observed 6 April 1793]
Very faint, much extended toward
position angle 70° north preceding to
south following [north-northwest to
south-southeast]. About 25' long, and
losing itself imperceptibly, about 6' or
7'broad. (HV-51)
GC/NGC: Very faint, extremely large,
much extended toward position angle
about 160°, very gradually brighter in the
middle.
IN LONG- EXPOSURE PHOTOGRAPHS TAKEN
with large telescopes, the barred spiral galaxy
NGC 4236 is a fantastic object, almost a visual
enigma. A glance at the photograph above can
give one the false impression that the galaxy's
gossamer arms have escaped the pull of gravity
and are fleeing wildly in all directions. Blotchy
patches of star formation pepper the arms, which
appear almost orphaned from the long, diffuse
bar that con-
stitutes the galaxy's brightest portion (the most
prominent patches are 5.5' southeast of the
galaxy's center). Indeed, the "SBdm" classification
means that this galaxy is a loose, clumpy, ragged
system with a prominent bar but an otherwise
rather faint disk.
About one-third of all galaxies have bars to
some degree. A bar may provide a galaxy's stars
a way to settle into stable orbits. Another
mechanism for forming galactic structure is
24 Deep-Sky Companions: The Caldwell Objects