In the Sky This Month

Two bright yellow-orange stars that are nearing the ends of their lives parade across the night sky. Capella, in Auriga, the charioteer, is high in the northeast at nightfall. Arcturus, in Bootes, the herdsman, rises around 10 p.m.

Spica, the brightest star of the constellation Virgo, will stand below the Moon at first light tomorrow, and farther to the lower right of the Moon on Friday.

M1, the Crab Nebula, stands near the tip of one of the bull’s horns, which is high in the sky this evening. You need a good telescope to see the nebula. It is the expanding debris from an exploded star. The star’s dead core sits at the nebula’s heart.

Cetus, the whale or sea monster, stands low in the southwest as night falls. The constellation is faint. But its brightest star, Diphda, is fairly easy to pick out, to the lower left of Venus, the “evening star.”

Regulus, the brightest star of the constellation Leo, is close to the right of the just-past-full Moon this evening and stays close throughout the night.

The planets Venus and Mercury are in the west as night falls. Venus is the “evening star,” so it’s easy to pick out. Smaller Mercury is much harder to see. It looks like a moderately bright star, but it’s much lower in the sky than Venus is.

Pollux and Castor, the twins of Gemini, line up almost directly above the Moon at nightfall. Pollux is closer to the Moon and is slightly brighter than Castor.

One of the jewels of the winter Milky Way stands high in the northwest this evening. It’s actually two jewels: a pair of star clusters known as the Double Cluster. They represent the jeweled handle of the sword of Perseus, the hero.

The North Star, Polaris, can be tough to find. One trick is to line up the stars that form the outer edge of the bowl of the Big Dipper. Follow that line up and away from the bowl to the next moderately bright star.

Shortly after sunset on any evening, look eastward to see Earth’s own shadow climbing into view. In a clear sky it forms a dark blue band below a band of bright pink or orange. The shadow climbs higher as the twilight fades.