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The constellation Coma Berenices refers to a
classical story concerning the hair of Berenice, the wife of Ptolemy
III of Egypt. While the story is an old one, the constellation is relatively
new, being introduced by Tycho Brahe (1546-1601).
As the evening's festivities continued, the shorn hair was discovered to
be missing. The priests might be sacrificed, if the queen's hair couldn't
be found. It was the astronomer Conon of Samos who came to their rescue
- proclaiming that Aphrodite had accepted the gift of Berenice's hair,
which now shown brightly in the heavens next to Leo.
The stars that form the constellation really aren't that remarkable to look
at, only a handful of fourth-magnitude stars, including three Bayer
stars. Yet there are several fine binaries,
eight Messier objects and the Coma Star cluster, not included in Messier's list.
From Denebola (beta Leonis) draw a line to the bright star to the
southeast, Arcturus (alpha Bootis). Alpha Comae is found on this line at about the midpoint.
Now proceed north from alpha Comae to beta Comae and then west
about the same distance to gamma Comae. These three stars form
half of a nearly perfect square. They aren't very prominent, and you
will have to have a nice dark night in order to study them.
Beta Comae is actually the brightest star in the constellation, and certainly the closest at 27 light years. It too has a diameter equal to the Sun.
Gamma Comae is an orange star about 260 light years away. It is in the
same region as the well-known Coma Star Cluster, but isn't a member of that group.
Alpha Comae is a rapid binary of two equal stars (5.05, 5.08). The companion orbits every 25.87 years and is presently decreasing; the current (2000) separation is less than 0.05". The orbit is an unusual one, seen perfectly edge-on.
Zeta Comae is a fixed binary: (6.0, 7.5; PA 237º, separation 3.6").
17 Comae and 24 Comae are two binaries with contrasting companions.
24 Comae is even more spectacular: a fixed binary with an orange
primary and emerald component. (5.2, 6.5; PA 271º, separation 20.3").
Struve 1639 is a closer binary: 6.8, 7.8; PA 327º, 1.6". This is a slow moving binary with an orbit of 678 years.
The constellation doesn't have a wealth of variable stars. We list the
two variables that might be of some interest.
R Comae is a long-period variable with period of 362.82 days, and
range of 7.1 to 14.6. Thus the maximums are nearly a year apart. In the
year 2000 the maximum should occur in the first week of December.
There are eight Messier objects (M53, M64, M85, M88, M91, M98, M99, and
M100), as well as a number of other fine galaxies, with NGC 4565 being
the best of the bunch.
However the best object is the unrivalled open cluster known as ‘The Coma Star Cluster’.
The cluster was once known as the tuft of hair at the end of Leo's tail. It now constitutes Berenice's golden tresses.
The cluster extends south from gamma Com (which is not, however, a member). At about 270 light years away, the cluster is one of the closest to our solar system.
M64, the Black Eye Galaxy, is a bright (8.5) compact spiral one
degree east-northeast of 35 Comae. The "black eye" can only be seen under
ideal conditions with large telescopes. The galaxy is over 20 million light
years away.
M85 is a bright spiral galaxy and member of the Virgo Galaxy Cluster,
most of which is found about five degrees further south. All the remaining deep
sky objects discussed also belong to this cluster.
M88 is a many-armed spiral galaxy some forty million light years away.
Quite bright (9.5), it's a favourite with many Messier observers.
M91 (NGC 4548) is another spiral galaxy, but is a rather confusing
object, sometimes being labelled M58. It is a rather faint galaxy (10.2) and
one wonders why, with so many galaxies in the region, spreading down through
Virgo, that this one was chosen by Messier.
M98 is a faint (10.1) spiral seen practically edge-on, lying just half
a degree west of 6 Comae.
M99 is roughly one and a half degrees east-southeast of M98. An open
spiral seen face on, its several arms are visible in large scopes. It has a
brightness of 9.8.
M100 is the largest of these spiral galaxies, although difficult to
appreciate in small telescopes. It's seen face-on, and has a brightness
of 9.4.
Coma Berenices has many more deep sky objects, particularly the southern
regions, where it borders Virgo. This is a fertile part of the sky to
investigate, as the evenings grow a little warmer and more inviting.
For a closer appreciation of Coma Berenices, visit the Binocular Section. |
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© Richard Dibon-Smith.