Perseus constellation can be observed in the northern hemisphere. The best period for observation in the southern regions of the middle latitudes is November and December, when it turns out to be at the zenith, that is, directly overhead. In the middle latitudes, it is visible almost all year round, with the exception of May and June, when it partially disappears below the horizon in the north. The easiest way to find this constellation is if you look up in late autumn or early winter and see the constellation Cassiopeia, which resembles the letter W. Under it and slightly to the south, you can see the rather bright star Mirfak (α Per). Perseus constellation itself resembles a compass. In an artistic interpretation, it represents a standing warrior holding the head of a Gorgon Medusa.
How can you see Perseus constellation in the sky? In large cities, because of the glare and dust, it is not so well visible, so animations and an image are prepared for you outside the city, in the mountains and if you look at it in space, from orbit.
There are two bright stars in the constellation Perseus – Mirfak (α Per) and Algol (β Per). Mirfak is the side or elbow of Perseus, the brightest star in the constellation, with a stellar magnitude of 1.79. The distance to it is about 590 light-years. It is a yellow-white supergiant with a diameter 62 times that of the Sun and a luminosity of 5,000 times. Although Mirfak is the brightest star in the constellation, it is definitely not the most interesting.
Algol is of the greatest interest. As already mentioned, Perseus constellation is depicted as a warrior with the head of a Gorgon Medusa in his left hand. Observing the constellation back in the Middle Ages, the Arabs noticed that one eye of Medusa was frozen and motionless, and the other winked from time to time. They were so amazed by this discovery that they called this eye Algol, which means “devil”. In Europe, Algol variability was first discovered in 1667 by the Italian astronomer and mathematician Montanari. However, he failed to figure out the pattern of the shine.
Another famous scientist, John Goodricke, did this. Having had scarlet fever as a child, he became deaf and dumb. From 1782 to 1783, every clear night, the scientist estimated the magnitude of the star and calculated a strict periodicity in the “wink” of the eye. For two and a half days, Algol has a stellar magnitude of 2.12. Then, for almost nine hours, its magnitude decreases to 3.39. Then it increases again to the previous value. Thus, the period between the two lows is 2,867 days. Goodricke explained this phenomenon as follows: “If it were not too early to speculate on the causes of variability, I could assume the existence of a large body orbiting Algol…” And for more than two hundred years Goodricke’s ingenious assumption remained only a hypothesis. Perhaps he would have continued his research, but at the age of 21, the scientist died of pneumonia.
In 1889, due to the observed periodic shifts of spectral lines, with a period of these shifts equal to the period of change in brightness, it was proved that the star is a binary. Thus, Algol became the first eclipsing variable star discovered by man. Relatively recently, it was revealed that Algol is not a double, but a triple star, with a mass ratio of 4.5 : 1 : 2 components. The star is located about 93 light–years away from us.
Other interesting objects of Perseus constellation
In addition to many stars, other interesting objects can be observed in this constellation – the double cluster χ and h Persei, the planetary and emission nebulae M 76 (the Little Dumbbell Nebula) and NGC 1499 (the California Nebula), respectively, the scattered cluster M 34, as well as the star in the vicinity of which naphthalene was discovered.
The double cluster χ and h is located on the “head” of Perseus, close to the constellation Cassiopeia. In good visibility conditions, away from artificial light sources, it can be seen with the naked eye. In addition to the beautiful sight, it is notable for being the radiant of the Perseids meteor shower, which appears annually on August 12 from the constellation Perseus. These two scattered clusters are about 100 light-years apart from each other, while they are more than 7 thousand light-years away from us.
There are also two well–known asterisms in the constellation – the Gorgon’s Head and the Perseus Segment. The Gorgon’s head includes the stars β (Algol), π, p and ω, forming an irregular quadrangle. The Perseus Segment is a prominent and eye–catching asterism in the shape of a huge crescent illuminated by the bright path of the Milky Way. It is formed by the stars δ, ψ, α (Mirfak), γ, n (Miram), τ, i and σ.
Mythology of Perseus Constellation
Perseus constellation has a three-letter abbreviation Per. It is recognizable, not very large – the twenty-fourth largest of all 88 constellations, and ancient. At the time of Ptolemy, it was included in the catalog of the starry sky (there were 48 constellations in total).
According to Greek legend, Perseus was the son of the Argos princess Danae and Zeus, the ancestor of Hercules. Danae was a descendant of Epaphus (the legendary king of Egypt), and he, in turn, was the son of Zeus and Io. Thus, Zeus was Perseus’ father and at the same time his maternal ancestor. Danae’s father was Acrisius, who dreamed of having a male heir. One day he asked the oracle if he would have a son. To which he received the answer that his wife Eurydice would not bear him a son, but his daughter Danae would have a son, his grandson, who would kill him in the future. Fearing the fulfillment of the prophecy, Acrisius ordered that Danae be placed in a copper tower and imprisoned there.
Zeus fell in love with the captive and, turning into a golden rain, was able to enter the dungeon, where he seduced her. Danae had a boy, who was named Perseus. Until the age of three or four, it was possible to hide the child, but then Acrisius found out about it. In anger, he ordered his daughter and grandson to be placed in a box that was dumped into the sea. Zeus and Poseidon helped them escape and delivered the box to the island of Serifos, which was ruled by the local king Polydectes. According to various versions, Perseus was raised either by Diktys, an ordinary fisherman who found a box and sheltered Danae and her son, or was sent to be raised in the temple of Athena.
When he grew up, he received an assignment from Polydectes to bring the head of the Gorgon Medusa, a monster whose gaze turned people into stone. With the help of Athena, Hermes and Hephaestus, Perseus defeated the Gorgon Medusa, cut off her head and took her and Pegasus with him. Even though the head was severed, the Gorgon’s gaze could still turn to stone. Returning home, he discovers the beautiful Andromeda chained to a rock. Struck by the beauty of the girl, Perseus falls in love with her. On the winged Pegasus, he, with the help of the severed head of the Gorgon Medusa, made the Cetus monster petrify. Having accomplished his brave feat, Perseus married Andromeda, and in their marriage they had several children.
Later, gymnastics competitions were held in the city of Larissa, where Acrisius was present as a spectator. Perseus took part in them. The disc he threw accidentally hit his grandfather’s leg and he subsequently died. According to another version, Acrisius went to Polydectes to demand the extradition of Perseus. However, at this time Polydectes dies, and funeral games were organized in memory of him, at which a disc thrown by Perseus hit Acrisius in the head, and he died on the spot. After these events, Perseus, being the only heir of Acrisius, did not want to rule Argos, “so as not to become king of the country ruled by a man who died through his fault.” So he swapped realms with his cousin Megapenthes and founded Mycenae, where they ruled with Andromeda in the future.
All the characters of the legend of Perseus’ rescue of Andromeda – Perseus flying on Pegasus, Andromeda, Cepheus, Cassiopeia and even the monster Cetus were captured in the starry sky with the same names. So that people will remember this incredible story for centuries.
Have you seen this constellation? Have its objects been observed with binoculars or a telescope? What is your favorite constellation? Share your impressions in the comments.
