Although it’s one of the 12 constellations of the Zodiac, Cancer the Crab is so faint that you’d likely never notice it … except for the lovely star cluster in its midst. This cluster is commonly known as the Beehive, or M44. Astronomers know it as NGC2632. An older name is Praesepe (manger or crib in Latin). The Beehive is a wonderful swarm of stars, glimpsed with the eye in a dark location and easily found in binoculars. Its size is 1.5 degrees, or three full moon diameters. Although the eye cannot detect them, it contains a thousand stars. Follow the links below to learn more.
How to see the Beehive star cluster. Keep an eye out for Regulus, and the Gemini stars Castor and Pollux, for they’re your guide stars to the Beehive star cluster. The Beehive star cluster is halfway between the Regulus and the Castor-and-Pollux pair.
In early March, look in the east after dark. You’ll probably see Regulus, the brightest star in the constellation Leo, rather close to the eastern horizon. Then the bright stars Castor and Pollux in constellation Gemini will catch your eye higher up in the eastern sky.
As the months pass, the Beehive will climb higher in the evening sky. It disappears from the western evening sky in late June, and returns to the eastern morning sky, starting around late August.
You’d think that an object with so many names – NGC2632, M44 Praesepe, Beehive – would be bright. But the Beehive star cluster isn’t bright. Only in dark country skies can you see this faint fuzzy object with the unaided eye. However, binoculars magically transform this smudge of light into a glittery swarm of stars.
… the nebulous mass in the breast of Cancer.
In ancient times, the cluster was used as a weather predictor. Pliny said:
If Praesaepe is not visible in a clear sky it is a presage of a violent storm.
Galileo had the first telescopic view of the Beehive in 1609. With his paper tube and two pieces of glass he was able to detect 40 stars.
Around 1769, Charles Messier added the cluster to his famous catalog of nebulous objects. Hence the designation M44 – the 44th object in Messier’s catalog.
The Beehive star cluster was known as a manger in Greek and Roman mythology. You might notice two bright stars on either side of the cluster with your binoculars, or you might see them unaided eye in dark skies. These two stars, Asellus Borealis and Asellus Australis. In skylore, these two stars represent the donkeys that Dionysos and Silenus rode into battle against the Titans.
The Beehive’s 1,000 stars. There are approximately 1,000 stars in the beautiful Beehive cluster, which is an open cluster of stars in our galaxy. Open clusters are stars that are gravitationally bound and are created out of the same star forming nebulae such as the stars in the Orion Nebula. The Beehive is one of the nearest open clusters to our sun and Earth. It has a larger population of stars than most other nearby clusters.
The Beehive open cluster’s distance is estimated to be between 520 to 610 light years from our solar system. If you use binoculars to see the Beehive, the brightest star you are seeing is 42 Cancri.
In September, 2012 two planets were found in the Beehive. They orbit two different stars and have been designated Pr0201b and Pr0211b. Both planets are hot Jupiters, that is, massive gas giants, in both cases orbiting very close to their stars. These two were the first planets detected orbiting stars like our own sun that were situated in an open star cluster. Planets had been found before in such clusters, but not orbiting stars like our sun.
Bottom line: Between the star Regulus in Leo and the stars Castor and Pollux in Gemini, you might notice a smudge – really a cluster of stars – called the Beehive.
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.