Sky and Telescope - May 2018 - 58

MAY 2018 OBSERVING
Going Deep Ted Forte

M AY 2 0 1 8 * S K Y & T E L E S C O P E

p THE QUEEN IN THE CLUSTER NGC 4889, an elliptical, is the largest of the galaxies in the
Coma Cluster and harbors possibly one of the most massive black holes known to date, weighing
in at some 21 billion solar masses.

northeast of NGC 4874, lies behind the
core of the cluster at around 460 million light-years. It appears small, faint,
and round. A number of small galaxies with PGC designations complete
the oval ring of satellite companions,
though they will require very large
aperture to trace out.
Some 5′ west of NGC 4874 lies the
close pair comprised of NGC 4864
and NGC 4867. On the night of April
11, 1785, William Herschel described

13h 00m

12h 40m

Coma Cluster

+30°

+25°

COMA BERENICES
M64
M53

+20°

5053
M85

Star magnitudes
4
5
6

three nebulae in the core of the Coma
Cluster. NGC 4889 and NGC 4874, the
two brightest galaxies in the cluster,
are certainly two of the three, but the
third is somewhat in doubt. Harold G.
Corwin speculates that the third nebula
might have been the combined glow of
NGC 4864 and NGC 4867 along with a
superimposed star that lies just southeast of NGC 4864's core. These two
galaxies are less than 1′ apart.
Corwin notes that the other likely
possibility for William Herschel's third
nebula might be NGC 4869, which lies
about 4′ southwest of NGC 4874. It is
one of the ﬁve brightest galaxies in the
heart of the cluster and appears round
with a bright core.
Some 8′ east-northeast of NGC 4889
is one of several concentrations of faint
but detectable galaxies that surround
the core of the cluster. My 30-inch
Dobsonian shows eight galaxies in
this quadrant easily enough. The three
brightest are NGC 4908, a 13.6-magnitude elliptical that has a brighter core,
IC 4051, a more elongated 13.2-magnitude elliptical, and IC 4040, classiﬁed
as a radio galaxy. Radio galaxies are a

N ASA / ESA

ent night, and, not recognizing them,
assigned them both new designations.
NGC 4886 is round with a bright core
and lies at approximately the same distance as its larger neighbor, around 300
million light-years.
Averted vision will reveal a pair of
similar galaxies about 2′ east-southeast
of NGC 4889. NGC 4898 is an elliptical galaxy that appears round, while
NGC 4894 is a lenticular galaxy, a
class of galaxies that are intermediate
between ellipticals and spirals. NGC
4894 lies about 100 million light-years
closer to us than the core of the Coma
Cluster. As with most giant galaxy
clusters, the center of the Coma Cluster
is populated with ellipticals. The spiral
galaxies that are associated with the
cluster are typically found in the outskirts, and the lenticular galaxies, such
as NGC 4894, are generally intermediate both in morphology and distance
from the cluster core. A little more than
1.5′ to the north of NGC 4889 is tiny
IC 4011, appearing as a small round
spot of uniform brightness. An elliptical, it is at a distance that puts it near
the center of the cluster.
Northwest of NGC 4889 at a separation of about 4.5′ is NGC 4883, a
small, round, barred lenticular galaxy
that has a brighter core.
The western giant, NGC 4874,
is surrounded by its own retinue of
smaller galaxies that form an oval ring.
Lying less than 1′ to the southwest is
NGC 4872, which has a somewhat
muddled discovery history. It was most
likely missed by William and Caroline
Herschel and possibly ﬁrst observed
by d'Arrest. Errors in position and an
ambiguous description by d'Arrest (his
notes could apply to any of three close
companions to NGC 4874) muddies the
waters. Moving counterclockwise, we
ﬁnd NGC 4871 a little more than 1′ to
the west of NGC 4874 and NGC 4873
about 1.5′ to the north. Both are similar
lenticular galaxies with small bright
cores. IC 3998, some 2.5′ to the east-

Sky and Telescope - May 2018

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