In the Sky This Month

Regulus will stand below the Moon at first light tomorrow. The brightest star of Leo is about 79 light-years away. That means the light we see from Regulus tonight actually left the surface of the star around 1939.

The Milky Way arches from northeast to southwest across autumn’s evening skies. Embedded in its star clouds is Cygnus, the swan. Cygnus flies south along the Milky Way with outstretched wings. Its tail is marked by the constellation’s brightest star, Deneb.

Perseus, the hero, is in the northeast at nightfall. Its brightest star, Alpha Persei, is about 50 million years old. That’s just one percent the age of the Sun, yet the star is nearing the end of its life because it is heavier than the Sun.

The Moon will be at last quarter tonight, as it lines up at a right angle to the line between Earth and the Sun. Sunlight will illuminate half of the lunar hemisphere that faces Earth.

Draco is in the north and northwest as night falls, above the Big Dipper. One of the dragon’s highlights is NGC 5907, an unusually flat spiral galaxy that is well above the end of the dipper’s handle.

The Moon passes especially close to the bull’s bright orange “eye” tonight. Aldebaran is just an eyelash away from the Moon as they rise in late evening. The Moon will pass even closer to the star over the following hours.

NGC 7252, the Atoms for Peace galaxy, is in Aquarius. The constellation is low in the southeast at nightfall, and scoots across the south during the night. NGC 7252 looks like electrons orbiting the nucleus of an atom.

Wedged into a cozy space between the well-known constellations Andromeda, Aries, and Perseus is tiny Triangulum, the triangle. Its three brightest stars form a long, thin wedge. It rises in the northeast in early evening.

Two “dog stars” chase across autumn’s pre-dawn sky. The brighter one is Sirius, in Canis Major, the big dog. The other is Procyon of Canis Minor, the little dog. Both are high in the sky at first light, with Procyon far to the upper left of Sirius.

Look in the west as twilight fades this evening for one of the most commanding stars in the sky: Arcturus, in the constellation Bootes, the herdsman. It shines pale yellow-orange.