NOAO / AURA / NSF
T
here are tens of thousands of them
in the Milky Way Galaxy. Given a
good, dark night sky you can see some
of them — with your telescope, your
binoculars, even your unaided eyes —
in any season. Yet we shouldn’t take
these objects for granted. And there’s a
season, even a particular month, that’s
arguably the best for viewing them.
The month I’m talking about is Feb-
ruary. The objects I’m talking about are
open star clusters.
Open season on open clusters.
The entire February evening Milky Way
— from the last peek of Cygnus in the
northwest to Puppis low in the southeast
— is splashed with open star clusters.
If we count the Double Cluster
of Perseus as a single attraction, the
number of open clusters marked on
our all-sky map for February is 18. This
includes two pairs of clusters that are
a little bit outside the gently luminous
band of the Winter Milky Way: the Ple-
iades (M45) and the Hyades in Taurus,
and M44 and M67 in Cancer. The other
14 clusters are closer to the galactic
equator, the central line in the equato-
rial plane of the Milky Way. In order,
from low in the northwest across the
celestial vault to low in the southeast
at the hour indicated on the chart, they
are: M39 in Cygnus; M52 in Cassiopeia;
the Double Cluster and M34 in Perseus;
M38, M36, and M37 in Auriga; M35 in
Gemini; M50 in Monoceros; M48 in
Hydra; M41 in Canis Major; and M47,
M46, and M93 in Puppis.
February’s Messier open clus-
ters by number. Let’s now say a thing
or two about each of the abovemen-A Month
for Open
Clusters
February’s night sky is awash
with sparkling targets.tioned Messier open clusters in order of
increasing Messier number.
We begin our numbered tour with
M34, a good low-magnitude telescopic
sight and intriguing naked-eye fuzzy
spot of light near Algol, or Beta (β) Per-
sei. M35 in the feet of Gemini is huge,
easy for the unaided eye in a dark sky,
and also so near the ecliptic that it’s a
prime target for the Moon and planets.
M36, M37, and M38 in Auriga are all
wonderful yet all different. While M36
and M38 are within Auriga’s pentagon,
the brightest of the three, M37, is just
outside the lines of that pattern. M39,
one of the last outliers of summer in
Cygnus, was likely observed by Aristotle
around 325 BC. M41 is a really bright
(magnitude 4.5) and handsome cluster
about 4° south of Sirius — why don’t
people observe it more? It’s certainly
plainly visible to the naked eye on a
dark, transparent night.
M44 and M45, the Beehive Clus-
ter and the Pleiades, respectively, are
already so renowned we’ll skip over
them here (don’t skip over them in
the sky, though!). M46 and M47 are
a delightful odd couple a little more
than 1° apart. M47 is brighter but with
stars of very different brightnessesirregularly distributed. M46, on the
other hand, comprises faint stars of
similar brightness arranged in a spheri-
cal gathering (a gathering that has a
planetary ne bula shining through from
behind it!). M48 was a “missing Mess-
ier” until it was identifi ed with the fi ne
open cluster NGC 2548 in Hydra near
Monoceros. M50 is in Moncoceros
and is a bright cluster with ill-defi ned
edges. M52 is a beautiful open cluster
in Cassiopeia.
Then the Messier catalogue almost
runs out of open clusters. The last by
number on our map are rich M67 near
Alpha (α) Cancri (Acubens) and M93 in
Puppis. M103 in Cassiopeia is appar-
ently a bit too faint for the map.
Globulars, anyone? This month’s
central sky chart in Sky & Telescope is
the only one of the year that doesn’t
display even a single globular star clus-
ter. If you feel compelled to see one at
the hour of our map, you can check out
the rather dim M79 in Lepus. But wait a
few hours and one bright globular after
another will start coming up. The fi rst
will be the great M3 in Canes Venatici.¢FRED SCHAAF welcomes your letters
and comments at [email protected].Under the Stars by Fred Schaafskyandtelescope.com• FEBRUARY 2020 45The oft-overlooked open cluster M41 lies around
2,300 light-years away in Canis Major.