The Caldwell Objects

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NGC 5248
Type: Mixed Spiral Galaxy
(SABbc)
Con: Bootes
RA: 13 h 37.5 m
Dec: +08° 53'
Mag: 10.3
Dim: 6.1' x 4.6'
SB: 13.8
Dist: 74 million light-
years Disc: William
Herschel, 1784
W. H ERSCHEL:
[Observed 15 April
1784] Very bright,
considerably large, extended from north preceding
to south following [from northwest to southeast].
Small bright nucleus. (Η I-34)
BOOTES, THE 13TH-LARGEST CONSTELLATION,
hosts the 4th-brightest star in the night sky (topaz
Arcturus) and a variety of variable and multiple
stars. But the constellation is a virtual deep-sky
wasteland for small-telescope users; sweeping its
907 square degrees with anything smaller than a
10-inch is visually unrewarding. Bootes lies too
far from the plane of the Milky Way to be
adorned with open clusters or nebulae. (One dim
globular cluster, NGC 5466, is camped beside the
southeastern edge of Canes Venatici.) And
though dozens of galaxies haunt the otherwise
hollow corridors of Bootes, only one is brighter
than magnitude 11.0 - NGC 5248, a magnitude-
10.3 spiral in the extreme southwestern corner of
the constellation, just 10' east of Virgo.
Robert Burnham Jr. calls NGC 5248 a
"normal" spiral galaxy. But what is normal? As
Timothy Ferris writes in his book Galaxies,
GC / NGC: Bright, large, extended toward position angle 150°,
pretty suddenly brighter in the middle to a resolvable nucleus.
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"The study of galaxies by human beings has
scarcely begun. Someone a century from now,
reading what we thought about galaxies, would
no doubt find much of it distorted, stunted or
simply wrong." Yet, from surveys of the visible
universe, astronomers have a pretty clear mental
image of what constitutes a "normal" spiral: a
symmetrical system, with a central nucleus in a
spherical bulge rimmed by a broad, flat disk,
itself a cosmic hurricane of star-studded arms
adorned with clusters, star-forming regions, and
nebulae both bright and dark. Like people,
galaxies have several degrees of normalcy. It's
normal for a spiral to have tightly wound arms or
loosely wound ones. It's normal for them to have
bars or to lack them. NGC 5248 is a classic
example of a highly symmetrical system with a
"mixed" disk structure that lies roughly midway
between these extremes — which also is normal.
The Caldwell Objects 179