Constellation Aquarius

The constellation Aquarius has been around a long time.  The Bablylonians named these stars “The Great One” after their god Ea.  The ancient Egyptians associated Aquarius with the annual floods of the Nile when these stars dipped close to the river.  The Greeks also associated these stars with water.  In some myths, Aquarius is the young Ganymede, who holds the water cup of the gods on Mount Olympus…

The faint stars of the constellation Aquarius lie in the expanse between the head of Pegasus and the the wide horned expanse of Capricorn, the Goat.  Look for the constellation just over the southern horizon in the northern hemisphere, and nearly overhead from the southern hemisphere in mid-evening hours in October and November.  There are no bright stars here, but the overall shape of the constellation is easy enough to trace.  The star Sadalmelik marks the right shoulder of the water bearer and Sadalsuud his left, and Sadachbia, Zeta (ζ), Eta (η), and Pi (π) indicate his right hand and the cup.  From the cup flows other “water constellations”, including Piscis Austrinus, Eridanus, Pisces, and Cetus, all of which lie in this part of the sky.

In binoculars, look especially around the area of Skat (delta Aquarii) and tau (τ) Aquarii.  The latter star is a wide double, one white and one orange, and there are many other fine faint stars visible nearby.

Constellation Aquarius (click to enlarge).

In the southern reaches of the constellations, just north of Capricorn, lie two tiny star clusters in a patch of sky just 3º wide.  First look for M72, the faintest globular cluster on Messier’s famed list. The cluster is a distant 55,000 light years away, which partly accounts for its low brightness of magnitude 9.3. The stars are hard to resolve in a telescope with objectives less than 8 inches in diameter, although a 4-inch scope at high magnification may reveal some granularity in the halo. The core appears somewhat diamond-shaped in a small scope.

M72

M72 is a fairly open globular cluster much like the more impressive and somewhat brighter and closer M71 in Sagitta. Look for M72 about 3.3º south-southeast of the 4th magnitude star epsilon (ε) Aquarii, less than a degree west of a 6th-magnitude orange star.

Now to a star cluster that’s not really a cluster at all, but rather a random alignment of four unrelated stars which Messier mistook for a cluster. This is M73 and it’s located about 1.3º east of M72.  M73 consists of just four stars of 10th and 11th magnitude in a tiny Y-shaped asterism about 1 arcminute across. In a telescope, use 100x to darken the background sky and bring out the best view. It looks like a stubby little rocket ship lost amidst a desert of background stars.

M73

Just 2 degrees northeast of M73 lies a small but bright and famous planetary nebula.  But let’s leave that for next time…