Introduction to Perseus

Extending the diagonal lines of the quadrangle in autumn, namely Alpha Pegasus and Alpha Andromeda, to twice the distance, there is a bright star with the apparent magnitude of 1.8m, which is the brightest alpha star in Perseus.

From the star map, the most striking sign of Perseus is the big arc drawn from η star, through γ, α, δ and ε stars, and all the way to ξ and ζ stars. People call it "the bow of Poerxiusi". China is called Tianchuan.

The center of the string connecting η star and ζ star at both ends of the Great Arc is Perseus β star, which was called Daling V in ancient China. If you think of the bright star of Perseus as a heroic Perseus, then the Great Ling Wu can be regarded as the magic eye on Medusa's head, which can turn people into stones at a glance, so westerners call it the "magic star". The beta star Perseus (Daling V) is an eclipse star, which is surrounded by two closely spaced stars in orbit. The period is 2 days 2 1 hour. When the dark star wraps around the bright star to block the light, it will drop from 2. 1 to 3.4, which takes about 10 hour.

Extend the γ and η stars at the top of Perseus arc to twice the distance, and observe carefully, there is a fuzzy spot here. In fact, these are two open clusters. Because they are close together, just like binary stars, they form the double star cluster.

M34 open cluster, about 1400 light years away from the earth, is visible with binoculars or small telescopes, and its size is about full moon. The brightest star in the cluster is 7 and so on. NGC869 and NGC884 (double star cluster η and χ in Perseus) are two open star clusters, which can be clearly seen by naked eyes, even with binoculars or small telescopes. They are all as big as a full moon.

In fact, there is a more important reason to call it a magic star, that is, its brightness will change, flickering, just like a mysterious magic eye. The brightness of Dalingwu changes very regularly. Every two days for 20 hours and 49 minutes, its brightness changes from 2.3 meters to 3.5 meters and then to 2.3 meters for a period of time. The ancient Arabs called Dalingwu "the devil in the forest", so it seemed to notice its darkening phenomenon at that time.