In the Sky This Month

Cepheus, the king, is a faint constellation not far from the Pole Star, Polaris. Look for it high in the north this evening. Its brightest stars look like a child’s drawing of a house, with a box of stars topped by a tall triangle.

BL Lacertae, a galaxy a billion light-years away, is firing a beam of energy in our direction — a “jet” of particles powered by a supermassive black hole. The galaxy is in the faint constellation Lacerta, which is in the northeast at nightfall.

Lacerta, the lizard, is high in the east-northeast at nightfall, outlined by a few puny stars. A decade ago, however, one of its stars produced the most powerful flare seen to that time. It was thousands of times stronger than any flare seen from the Sun.

The stars Sirius and Procyon are in the east and southeast at first light. Sirius is the brightest star in the night sky. Procyon is to the upper left. The name Procyon means “before the dog,” meaning it precedes Sirius, the Dog Star, into the sky.

One of the most popular astronomical events of the year happens tonight: the Harvest Moon. It is the full Moon closest to the autumnal equinox, on September 23rd. The time of the full Moon is near midnight, when the Moon lines up opposite the Sun.

The star cluster Messier 39 stands high in the northeast at nightfall, to the lower left of Deneb, the bright star that marks the tail of Cygnus, the swan. A good pair of binoculars will allow you to see the entire cluster in a single view.

The globular cluster M15 arcs across the sky this evening. It is a family of more than a hundred thousand stars packed into a tight ball. M15 is in the east-southeast at nightfall, well to the upper right of the Great Square of Pegasus.

Neptune, the most distant of the Sun’s major planets, is at opposition, as it lines in the opposite direction from the Sun. It is in the sky all night and shines brightest for the year, although you still need optical aid to pick it out.

Cassiopeia is a third of the way up the northeastern sky as night falls. Its stars form a letter “W.” The brightest star, Schedar, is at the bottom right point of the W. It is a young star, but so massive that it’s already nearing its end.

Look for Saturn to the right of the Moon tonight, shining like a bright star. Strong binoculars or a telescope will reveal its biggest moon, Titan, which looks like a tiny star near the giant planet.