March 18, 2008

In Today's One Minute Astronomer...

M44: A Hive Of Celestial Bees

A springtime beauty, the Praesepe or “Beehive” open star cluster is easily visible to the naked eye as a misty cloud. But its true nature and striking beauty are revealed only with help of binoculars or rich-field telescope.

The Basics

• One of the few star clusters known since antiquity, the Beehive was called the "Little Cloud" or "Cloudy Star" by Hipparchus. The ancients used the cluster as a weather indicator: if it was invisible, then violent storms were on the way.

• The Beehive is fairly bright (magnitude 3.7) but, unlike the Pleiades, can't be resolved into individual stars with the naked eye.

• The cluster lies about 580 light years from Earth and stretches 16 light years across. It appears about 3 times the size of the full moon, so examine it with your binoculars or telescope with a wide-field eyepiece to see its full glory.

A Deeper Look

• Galileo was first to turn a telescope toward this "nebulous" object, and reported: "The nebula called Praesepe, which is not one star only, but a mass of more than 40 small stars." Can you imagine the excitement of first discovering the nature of this mysterious cloud, known since antiquity?

• With larger telescopes, more than 200 stars have been confirmed as members. Astronomers determine which stars are members of the cluster by measuring the “common motion” of the stars… if they're all going in the same direction, they're assumed to be from the same cluster.

•The Beehive emerged out of a great diffuse gaseous nebula some 730 million years ago. Some believe it has a common origin with the Hyades cluster, which forms the “V” in Taurus. The two clusters have since separated, but they're still headed in the same direction.

A Bit of History

Because of its nebulous appearance, the ancient Japanese believed the cluster was a lump of souls, and the sight of it terrified them. It's called “seki shiki”, which translates as “piled corpse spirits”.

Personal View

"Corpse spirits" notwithstanding, the Beehive presents a welcome sign of the beginning of Northern spring. And it's a magnificent sight in binoculars or wide-field telescope.