Perseus - The Rescuer of Andromeda

Perseus is a fall and winter constellation for observers in the Northern Hemisphere. Perseus is located southwest of the 'W' of Cassiopeia's chair. It appears as a somewhat bent, V-shaped pattern of stars.

As Perseus rises in the late summer, the Earth passes thorough the tail of comet Swift-Tuttle. This produces a rich rain of shooting stars that seem to stream toward us from Perseus. This meteor shower is known as the Perseids. The meteor shower coincides with the rising of the constellation in late August.

History and Mythology

Perseus was the Greek hero sent to kill the evil Medusa and to bring her serpent-crowned head back to Minerva. The hideous Medusa was said to be able to turn anyone who looked at her into stone. To arm himself, Perseus was given the shield of Minerva, which was polished like a mirror. Mercury gave him his shoes with wings. Pluto gave him a helmet of invisibility.

Perseus found the Medusa sleeping, and using the reflection from the shield, he was able to aim his sickle and decapitate the creature in one blow. He attached her head to his belt and began his trip home.

As he flew across the sea some drops of Medusa's blood fell into the ocean. These drops were felt by the sea god Neptune, who had loved Minerva when she was young and beautiful. Neptune caused the blood to mix with the sea foam and the sand to create Pegasus, the beautiful winged horse.

In Perseus' travels, he came to meet King Atlas. Atlas looked at the face of Medusa and was immediately turned to stone. From that time on, Atlas had to bear the weight of the world on his shoulders.

As Perseus continued his trip home, mounted upon the winged horse Pegasus and carrying the gruesome head, he came upon the beautiful Andromeda chained to a rock by the sea. One glance from the Gorgon's head turned Cetus to stone and saved Andromeda from this sea monster. In the sky today, Perseus still holds the Gorgon Medusa's head. The monster's eye is the variable star Algol, known as the Demon Star.

Notable Stars

Perseus lies along the Milky Way, not far from Cassiopeia. Its upper stars form a curve, and along the west side is Algol, the Demon star. The brightest star in Perseus is Mirfak, meaning "the elbow". It is a blue-white supergiant of second magnitude. It is located about 600 light-years away.

Beta Persei or Algol, whose name in Arabic means "head of the demon", has a sinister reputation. Ancient astronomers thought it to be the most violent and unfortunate star in the sky.

Algol is the best known example of an eclipsing binary star in the sky. Normally magnitude 2.1, a companion star passes in front of Algol every 2.87 days and blocks it from our view. Algol then dims to magnitude 3.4 for about 10 hours. There is also a secondary eclipse when the brighter star occults the fainter secondary, but this secondary eclipse is much fainter.

Clusters, Nebulae, and Galaxies

The finest star clusters in Perseus are the beautiful pair NGC 869 and NGC 884, known together as the famous Double Cluster. With the naked eye, they appear as fuzzy stars. In binoculars or a small telescope at low power, the two clusters are seen together with hundreds of stars sparkling against the background of the Milky Way.

Between Perseus and Andromeda is M 34, an open cluster of 5th magnitude. There are about 80 stars in the loose cluster, which is about 1,400 light-years away.

M 76 is is one of only four planetary nebulae in Messier's catalog. It is also known as the Little Dumbbell Nebula; at 10th magnitude, it is also one of the faintest Messier objects. M 76 does not have the usual circular disk shape of most planetary nebulae; instead, it exhibits two bright nodules with a pinched center and irregular nebulous filaments coming out of both ends, surrounded by a much fainter, diffuse outer shell.

NGC 1499 is a large, 4th magnitude nebula called the California Nebula; its low surface brightness makes it difficult to see visually, but it makes spectacular photographs. M 76 is a small, 12th magnitude planetary nebula in Perseus's western part. It has irregular, nebulous filaments coming out of both ends with a pinched center.

For larger telescopes, NGC 1333 is catalogued as a reflection nebula in Perseus, but is actually part of the Perseus OB2 molecular cloud complex, and an area of active star formation. This star-forming region, located roughly 1,000 light-years from Earth, harbors hundreds of newly formed stars less than one million years old. NGC 1491 is an emission nebula just over a degree NW of Lambda Persei.

Perseus is also home to the Perseus Cluster of galaxies. The brightest member of this cluster (NGC 1275) is also known as the radio source Perseus A.