In the Sky This Month

The planet Saturn perches just above the Moon at first light tomorrow. It looks like a fairly bright star. The much brighter planet Jupiter stands to their left. It will appear close to the Moon on Wednesday.

Gamma Virginis, one of the brighter stars of Virgo, consists of two stars that are near twins. Both are about half-again the mass of the Sun, and just a quarter the age of the Sun. The system is above Spica, Virgo’s leading light, in the east-southeast at nightfall.

Alpha Sextantis crossed the celestial equator less than a century ago and will continue moving southward for millennia. The star is in the southeast as night falls. Under dark skies, it is just visible, to the lower right of Regulus, the heart of Leo.

The star clusters Messier 46 and 47 are in the south at nightfall, not far to the upper left of Sirius, the brightest star in the night sky. M46 is to the left of its brighter neighbor. They are so close together that they’re in the same binocular field of view.

The constellation Puppis is low in the south at nightfall. One of its highlights is HD 69830, a star system with three giant planets. It stands well to the left of Sirius, the brightest star in the night sky, and is an easy target for binoculars.

Zeta Puppis is the brightest star of the constellation Puppis. It represents the poop deck—the elevated deck at the stern of the Argo, the boat that carried Jason and the Argonauts. The constellation is due south as night falls, just above the horizon.

Argo Navis represented the boat that carried Jason and the Argonauts. In the 1700s, it was split it into three smaller constellations: Puppis, the poop deck; Vela, the sail; and Carina, the keel. Puppis, the largest piece, is atop the southern horizon at nightfall.

From the late 1600s until the early 1800s, astronomers drew many new constellations. Many of their creations have since vanished. An example is Cerberus, a three-headed snake in the hands of Hercules. It is low in the west at dusk, below the bright star Aldebaran.

The full Moon has a follower tonight: Spica, the leading light of Virgo. It’s below the Moon as it climbs into good view by 9 or 10 p.m., and closer to the lower left of the Moon at first light tomorrow.

AR Cassiopeia is one of only two systems known to contain seven stars. It’s in Cassiopeia, which is in the northwest at nightfall. AR Cas is below the bottom point of the W formed by the queen’s brightest stars. Under dark skies, it’s just visible to the naked eye.