Greek mythology is full of heroes, but the greatest of them all was Perseus. Destined to become the great grandfather of the famous Hercules, Perseus had a rough start in life. King Acrisius of Argos was told by an oracle that he would be killed by his grandson, so he locked his only daughter, Danaë, in a dungeon, so that she could never bear him a grandchild that could fulfill the prophecy.
But the gods, as usual, had other plans, starting with Zeus ( Jupiter), who lusted after the beautiful Danae, and came to her disguised as a shower of golden coins that fell into her lap, and impregnated her. She gave birth to a son, and named him Perseus. When King Acrisius heard about this, he locked both mother and son inside a wooden chest and had it cast into the sea. But the gods did not allow the chest to sink, and guided it to the island of Seriphos, where a fisherman, Dictys, rescued them and brought up Perseus as his own son.
Perseus grew into a man of great strength and bravery, but his troubles were not over. When his mother refused the advances of King Polydectes of Seriphos, the king took her by force, after sending Perseus on a mission to bring back the head of the gorgon Medusa. The head was so hideous it turned anyone who looked upon it to stone, and Polydectes was certain he was sending Perseus to his doom, and rid of him forever.
But once again, the gods had other plans. Athena gave Perseus a bronze shield that shone like a mirror. Hephaestus gave him a diamond sword. Hermes (Mercury) gave him a gift of winged sandals, and Hades (Pluto) placed on his head a helmet of darkness that rendered him invisible. Perseus used the wings of Hermes to travel to the far shores where Medusa lived. Being invisible, he was able to sneak up on the creature, and looking only at her reflection in his shield so he wouldn't turn to stone, Perseus used the sword of Hephaestus to cut off the Gorgon's head.
From the blood of the slain Medusa sprang the winged horse, Pegasus, whom Perseus mounted to make his way back to Seriphos. As he flew over the lands of Ethiopia, he heard the cries of the princess Andromeda, whom he rescued and carried off to be his wife.
He arrived back on the island of Seriphos to find his mother in the clutches of King Polydectes. Perseus rescued her, and forced Polydectes and his followers to gaze upon Medusa's head, and they were all turned to stone. He then presented the head of Medusa to the goddess Athena, who set it in the middle of her shield. Finally, during an athletics contest, Perseus threw a discus that accidentally went astray, hitting and killing a spectator in the crowd. The spectator turned out to be the grandfather of Perseus, King Acrisius, thereby fulfilling the prophecy the King had tried so hard to avoid - that he would be killed by his grandson.
Being one of the gods' favored sons, Perseus was placed in the stars to live forever.
Sitting directly in the middle of a dense part of the Milky Way, Perseus is not the easiest figure to identify. In 285 BC, Greek poet Aratus described him as "dust-stained". The brightest star in the constellation is Alpha Persei, named Mirphak, from the Arabic "Marfik al Thurayya," elbow of the Pleiades. It is one of three stars (along with Menkib and Atik) with ancient Arab names that refer not to the figure of the hero, but to the famous, bright star cluster directly below it, the Pleiades. Scholar R.H. Allen speculates, "this may indicate a different representation of Perseus in their day." The star is sometimes known as Algenib, Arabic for side, which is more anatomically correct, but in direct conflict with the star of the same name in Pegasus. Mirphak is an F5I yellow supergiant 5,000 times brighter than our Sun. Far away at 570 light years, it still manages to shine in our sky with the bright magnitude of 1.79. Mirphak is at the centre of an open star cluster called The Alpha Persei Cluster, or Melotte 20.
Beta Persei is Algol, Arabic for the ghoul. It is famously known as The Demon Star, and throughout ancient and medieval times was considered the most dangerous and unfortunate star in the heavens. To the Hebrews it was "Rosh ha Satan", or Satan's Head. It is also associated with the sinister "Liluth," the mysterious first wife of Adam.
The evil connotations of this star are due in no small part to the fact that it is one of the most famous variable stars in the sky. Every 2.867 days, the star begins to dim, and over the course of five hours, it fades from a magnitude of 2.1, down to a magnitude of 3.4. Then it begins to brighten again, and five hours later it is back up to 2.1 again. It is easy to see how ancient cultures could have viewed this as the slow blink of a malevolent eye.
Modern times have revealed the star to be a close eclipsing binary, where one star regularly crosses in front of the other, causing it to dim, and then brighten again. The brighter of the pair (Algol A) is a B8V blue/white main sequence star, and its companion (Algol B) is a much dimmer K0III orange giant that passes in front of Algol A - you guessed it - every 2.867 days. A third star, Algol C, orbits the other two every 681 days, making Algol a triple star system.
Below Algol is a small, upturned circlet of three dimmer stars that mark out the head of the Gorgon Medusa, as it is carried by Perseus across the sky. In clockwise fashion, the first of these is Pi Persei, named Gargonea Secunda, a blending of Arabic and Latin. At magnitude 4.68, it is a relatively dim A3V white main sequence star, about 310 light years away.
At magnitude 3.32, Rho Persei, Gargonea Tertia, is the brightest of the three stars. It is an M4III red giant, about 307 light years away.
The last Gorgon star is Omega Persei, named Gargonea Quarta, another rather dim star at magnitude 4.61, it is a K0III yellow/orange giant, about 288 light years away.
Although Allen leaves this star unnamed, Eta Persei is labelled Miram on all the star charts, but no-one seems to know why. It is a K1III yellow/orange giant with a magnitude of 3.77, out at the great distance of 880 light years.
Xi Persei has the ancient name of Menkib, from the Arabic "Mankib al Thurayya", shoulder of the Pleiades, (just below it). It is a rare, extremely hot O7I blue supergiant with a surface temperature of 37,000 degrees K. It has a luminosity 13,000 times greater than our Sun, allowing it to shine in our sky at magnitude 3.98, even though it lies at the very great distance of 1,254 light years. It has a small, dim companion that orbits it every seven days.
Omicron Persei is named Atik, from the Arabic for collarbone, once again traditionally alluding to the nearby Pleiades, and not the hero. It is a very close binary system, with a hot B1III blue giant and a B3V blue main sequence star orbiting each other every 4.42 days. Like Menkib, the system is very far away at a distance of 1,125 light years, and shines with a combined magnitude of 3.84.
There are six known planetary systems in the constellation Perseus. All the stars are beyond naked eye visibility, and all the planets are gas giants unlikely to harbour life. For more information on these and other extrasolar planets, visit NASA's New Worlds Atlas, and The Open Exoplanets Catalogue.
Perseus has two Messier objects, the first being M34 (NGC 1039), an open star cluster. Measuring 15 light years across, it is estimated to contain about 100 stars. The group has a a magnitude of 5.5, from 1,400 light years away.
M76 (NGC 650/651) is a planetary nebula, its connection to a planet in name only, being a shell of expelled gas from a dying star at its centre. It also goes by the name of The Little Dumbbell Nebula, from its similarity to M27, the Dumbbell nebula. With a magnitude of 9.6, it is faint but reachable in a small telescope. Its distance is difficult to determine, according to SEDS between 1,700 and 15,000 light years.
The most famous star cluster in Perseus is the Perseus Double Cluster, two charming clusters named NGC 884, and NGC 869. The two open clusters are right beside each other at magnitude 6.1 and can be seen in the same field of view, shown in the image below.
NGC 1333 is a huge cloud of gas and dust a thousand light years away where stars are being born, lit up by the blazing, fiery light of new born stars.
NGC 1275 is a giant, active, elliptical galaxy, 237 million light years away with a magnitude of 11.9. It is an unusual galaxy in that long gaseous filaments extend out from the galaxy into space, created by the powerful magnetic field generated by a massive black hole at the center of the galaxy. NGC 1275 is near the middle of a large group of galaxies called the Perseus Galaxy Cluster.
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