Big, Bold, Bright, Beautiful
68 JANUARY 2020 • SKY & TELESCOPE
compared to the others, makes it very bright indeed, more
than 100,000 times brighter than the Sun. The cluster itself
is pretty, too, with a loose scattering of relatively bright stars
surrounding the central luminary. Many of these stars are
intrinsically bright, hot O- and B-type stars, which means
they’re relatively young (around 5 million years). Indeed, this
is one of the youngest known clusters.
A little higher and to the east you’ll fi nd one of my favorite
open clusters of all: M46. M46 is a beautiful dusting of
delicate stars of magnitudes 10–13, but it comes with a bonus
Easter egg: a planetary nebula directly in line with the cluster.
The planetary nebula, NGC 2438, is relatively large and easy
to spot under dark sky, and one of the cluster stars shines
through to masquerade as the central star (which isn’t visible
itself in a normal-sized amateur scope).
The cluster stands out well in binoculars and is best appre-
ciated at low power in a telescope... until you zoom in and
see how many more stars appear. This is an eye-pleaser at any
magnifi cation, in any aperture. In fact, it’s just visible to the
naked eye under a dark sky.Winter’s Splendors
Object Designation Type Mag(v) Size/Sep RA Dec.
Orion Nebula M42 Emission nebula 4.0 65 ′ × 60 ′ 05 h 35.4m –05° 27′
Trapezium Theta^1 Orionis Open cluster 4.7 18 ′′ 05 h 35.3m –05° 23′
Rigel Beta Orionis Double star 0.3, 6.8 9.4′′ 05 h 14.5m –08° 12′
M78 Refl ection nebula 8.3 8 ′ × 6 ′ 05 h 46.7m +00° 03′
Analemma Cluster Collinder 91 Open cluster 6.4 14 ′ 06 h 21.6m +02° 20′
M35 Open cluster 5.1 25 ′ 06 h 09.0m +24° 21′
NGC 2158 Open cluster 8.6 5 ′ 06 h 07.4m +24° 06′
M37 Open cluster 5.6 15 ′ 05 h 52.3m +32° 33′
M36 Open cluster 6.0 10 ′ 05 h 36.3m +34° 08′
M38 Open cluster 6.4 15 ′ 05 h 28.7m +35° 51 ′
NGC 1907 Open cluster 8.2 5 ′ 05 h 28.1m +35° 19′
Kite Cluster NGC 1664 Open cluster 7.6 18 ′ 04 h 51.1m +43° 41′
Alpha Persei Cluster Collinder 39 Open cluster 2.3 5° 03 h 24.3m +49° 52′
Dragonfl y Cluster NGC 457 Open cluster 6.4 20 ′ 01 h 19.5m +58° 17′
Chipmunk Cluster NGC 1342 Open cluster 6.7 17 ′ 03 h 31.7 m +37° 22′
Almach Gamma Andromedae Double star 2.3, 5.0 9.7′′ 02 h 03.9m +42° 20′
NGC 752 Open cluster 5.7 75 ′ 01 h 57.6m +37° 50′
Tau Canis Majoris Cluster NGC 2362 Open cluster 3.8 6 ′ 07 h 18.7 m –24° 57′
M46 Open cluster 6.1 20 ′ 07 h 41.8m –14° 49′
NGC 2438 Planetary nebula 10.8 1.2′ 07 h 41.8m –14° 44′
M47 Open cluster 4.4 25 ′ 07 h 36.6m –14° 29′
Angular sizes and separations are from recent catalogs. Visually, an object’s size is often smaller than the cataloged value and varies according to the aperture and
magnifi cation of the viewing instrument. Right ascension and declination are for equinox 2000.0.While you’re in the neighborhood, check out M47, a larger
and coarser cluster about 1° to the west. It’s close enough to
fi t in the same binocular fi eld as M46.
You’ve probably noticed by now that the majority of the
big, bold, bright, and beautiful objects of winter are open
clusters. Why is that? Because in the winter we’re looking
outward toward the rim of the Milky Way, right down the
length of the Orion Spur in which we live and into the Per-
seus Arm, both of which are full of clusters. Why no globular
clusters? Because those hang out closer to the core of the gal-
axy, which is visible in the summer. Look for another article
in six months dealing with some of those.¢ Contributing Editor JERRY OLTION enjoys pareidolia, as you
can tell by the names he gives open clusters. Contact Jerry at
[email protected].FURTHER READING: For more “big, bold, bright, and beauti-
ful” targets, see Jerry Oltion’s spring and fall collections in the
May 2018 and October 2018 issues, respectively.