OF THE ROGER N. CLARK

MI00 (NGC 4321), GALAXY IN COMA
BERENICES
R. A. 12h 22.9m, Dec. 15° 49' (2 000.0)
Technical. M 1 00 is a spiral galaxy of class
Sc seen nearly face-on. Its distance is estimated
to be about 40 million light-years and
its linear diameter slightly more than 100 000
VISUAL ASTRONOMY OF THE DEEP SKY
light-years. The galaxy's total luminosity is
about 20 billion times that of our Sun, its
mass about 160 billion suns. There are two
main spiral arms and complex dust lanes.
The arms can be followed all the way in to
the nucleus.
y l SU •
-;':-- al In small to medium telescopes,
MIOO appears as a bright central spot surded
by a uniform, diffuse glow. . The total
nitude is 10.4 and the diameter 5 arc-
. tes ThiS corresponds . to a mean sunace
ng nd The main spiral arms are only 3 arc-
h' h'
I h
roun
. r
mag
mInU .
b . htness of22.6 magmtudes per square arc-
minutes across, w IC IS olten as arge as t e
se eo .
A VISUAL ATLAS OF DEEP-SKY OBJECTS
Co
galaxy appears. The arms beyond 3 arcminutes
are quite faint and low in contrast
even under excellent skies.
In the 8-inch, no spiral structure could be
detected under moderate to good skies. Some
observers have reported hints of spiral arms
in medium size telescopes.
•
-- 5' --
Photograph of MIOO. South is up . (Courtesy Evered
Kreimer, The Messier Album.)
Scale: 1.2 arc-min/cm
8-inch fl 11.5 Cassegrain
20mm Erfle (11 7 X )
l 2.4mm Erfle (188x,
best view)
Drawing of MIOO.
Viewing Distance (cm)
25X:115 200X:14
50 X: 57 300 X : 10
100x: 29 400X : 7
air mass: 1.28, faintest star: 13.8 at zenith, 188x;
no tracking
5/15/83 9:55-10:12 UT at Barbers Point, Hawaii;
R. Clark
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