Perseus


Perseus


English namePerseus

Major
stars
alpha PerseiMirfakmagn. 1,8RA: 03h 24m 19.37sDec: +49 51' 40.4"
beta PerseiAlgolmagn. 2,1RA: 03h 08m 10.13sDec: +40 57' 20.4"
gamma Perseimagn. 3,1RA: 03h 04m 47.79sDec: +53 30' 23.2"
delta Perseimagn. 3,1RA: 03h 42m 55.48sDec: +47 47' 15.3"
epsilon Perseimagn. 3,0RA: 03h 57m 51.22sDec: +40 00' 36.7"
zeta PerseiAtikmagn. 2,9RA: 03h 54m 07.92sDec: +31 53' 01.0"

DescriptionThe constellation of Perseus appears as an overturned Y, among Cassiopeia, Andromeda, Auriga and Taurus.

The most remarkable star of the constellation is certainly Algol, an eclipse binary, formed by two component that, seen from Earth, periodically pass the one before the other: the brightest component, Algol A, is a white star about 100 times more shining than the Sun; its companion, Algol B, is instead an orange star, greater but less bright. The eclipses of Algol happen every 2 days, 20 hours and 49 minutes: in five hours Algol lowers to a third of its normal brightness, passing from the magnitude 2,1 to the magnitude 3,4; after other five hours it returns to the usual shine. The phenomenon is visible to the naked eye.

NGC 884 and NGC 869Near Cassiopeia there is the Double Cluster, whose components are two different stellar clusters: NGC 869, more crowded and distant about 7500 light-years, and NGC 884, which is 7200 light-years away and is older, considering that it contains some red giants (that is stars in an advanced period of evolution).


Mythology
and history
Son of Zeus and Danae, Perseus was born in a bronze tower where Acrisius, king of Argus, imprisoned his daughter Danae because an oracle had announced him that he would have died for work of a child of her. But Zeus saw the segregated girl and fell in love with her: to possess her the god changed into a golden rain, succeeding in penetrating through the holes of the tower. When Perseus was born, Acrisius tried to put an end to the life of his daughter and his grandson, by closing them in a basket that he threw in the sea. But Danae and Perseus, protected by Zeus, landed safe and sound to the island of Seriphus, where they were welcomed by the fisherman Ditti.

When he had grown up, Perseus was forced by Polidettes, king of Seriphus, to bring him the gorgon Medusa's head: the exploit was apparently impossible, since whoever had seen the gorgon's face would have been petrified. With the help of the goddess Athena, Perseus succeeded in approaching Medusa and beheading her, looking her image reflected in the bronze shield. In the sky Perseus appears while he is holding the head of the gorgon (whose eye is represented by Algol). From the blood trickled from the cut-off neck of the gorgon, Pegasus, the winged horse, was born.

While Perseus was going back to Seriphus, he saw a young girl chained to a cliff near the sea: she was Andromeda, who was about to be devoured by a sea monster. Perseus attached it and killed it showing the Medusa's head. Then he married Andromeda and they had a child, Perses.

Perseus then returned with his wife to Seriphus, where he avenged himself on Polidettes petrifying him. Neither Acrisius, Danae's father and Perseus' grandfather, escaped his fate: he was accidentally killed by a disk launched by his grandson during a competition.


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