In the Sky This Month

One of the most beautiful double stars is Algieba, in Leo, the lion, a constellation that is prominent during spring. Seen through a telescope, both of Algieba’s stars shine golden yellow.

M82, a galaxy that is a factory for exploding stars, loops high across the northern sky tonight. It stands to the upper left of the bowl of the Big Dipper as darkness falls. M82’s most recent supernova blasted into view four years ago.

Hercules climbs into prominence during spring. Most of its stars clear the northeastern horizon by about 11 p.m. Look for a pattern of four moderately bright stars that looks like a shield. This pattern, the Keystone, represents Hercules’ body.

The stars Procyon and Sirius arc to the lower right of the Moon as night falls and wheel down the western sky later on. Sirius is the brightest star in the night sky. Procyon, which is much closer to the Moon, is in the top 10 as well.

A gazelle leaps past the Big Dipper. In ancient skylore it made three leaps, each marked by a pair of stars. Those that mark the first jump are Alula Borealis and Alula Australis. As night falls, they are almost due east, far to the right of the dipper.

The Moon is at first quarter today, exactly one-quarter of the way through its month-long cycle of phases. It lines up at a right angle to Earth and the Sun, so sunlight illuminates half of the lunar hemisphere that faces our way.

The Orion Nebula, a stellar nursery, hangs below the hunter’s belt at nightfall. A binary star known as Iota Orionis is near the nebula. An encounter with another binary may have kicked one star from each system out into space, with the remaining stars forming a new binary.

Aldebaran, the bright eye of the bull, stands just below the Moon at nightfall, and leads the Moon down the sky later on. Aldebaran is just 65 light-years away. It is a bloated star near the end of its life.

The constellation Coma Berenices, which represents the hair of a legendary queen, is well up in the east by mid-evening. It is about half way between the bright stars Arcturus and Regulus, which highlight the eastern sky.

Spring arrives in the northern hemisphere today, but the most prominent stars of winter remain in good view. They form a big loop known as the Winter Circle, which is in the southwestern quadrant of the sky this evening.