In the Sky This Month

Hydra, the water snake, is the largest of the 88 constellations. It is so faint, though, that it is tough to see. It serpentines across the south tonight, all the way from Cancer to Libra.

Izar, the second-brightest star of Bootes, is one of the most prominent binaries in the night sky. It stands to the left of brilliant Arcturus, the constellation’s brightest star, which is half way up the eastern sky at nightfall.

Two giant star clusters are visible in the constellation Hercules. Each consists of hundreds of thousands of stars packed into a ball that’s only a few dozen light-years across. Known as M13 and M92, they are in the northeastern sky at nightfall.

The Moon anchors a pretty lineup this evening. The planet Mars looks like an orange star to the upper right of the Moon. El Nath, at the tip of one of the horns of the bull, is farther to the right of Mars. It is about the same brightness as Mars now.

Aldebaran, the bull’s bright eye, puts in one final good evening showing tonight. It is close below the Moon after sunset. It is so low in the sky that it would be hard to spot on its own. But Aldebaran’s proximity to the Moon will help it stand out.

Orion is low in the west as night falls. Its brightest star, Rigel, is so low that you might not be able to see it. But Orion’s three-star belt is in view, parallel to the horizon. Bright Betelgeuse is above the belt, still in view at nightfall.

The Eta Aquarid meteor shower should be at its peak in the wee hours of Monday morning, with perhaps a few dozen meteors per hour. But the shower is spread out, so you can see a fair number of meteors for a few nights before and after the peak.

The modest constellation Corona Borealis, the northern crown, climbs the eastern sky this evening. It is a delicate semicircle of seven stars that really does resemble a crown.

Leo stands high in the south in early evening. A curved pattern of stars forms the lion’s head, mane, and forelegs, while a triangle of stars makes up his hindquarters and tail. When you put these two patterns together, they resemble a lion.

Today is Beltane, an ancient Celtic festival celebrated with bonfires. It is a cross-quarter day, which falls roughly half way between a solstice and an equinox. In many cultures, these dates marked the start of the seasons, so May 1 was the first day of summer.