This November doesn’t offer a rich assortment of astronomical phenomena, such as spectacular planetary conjunctions, but the constellations do provide astronomers with an opportunity to relate a very colourful story.
Andromeda and Perseus
Our tale begins in Antiquity, in the royal court of Ethiopia. It is there that the three protagonists of our story are to be found: King Cepheus, Queen Cassiopeia, and their daughter Andromeda. One day, Cassiopeia, who was quite boastful, insisted that Andromeda was more beautiful than the Nereids — sea nymphs renowned for their incomparable attractiveness. Outraged by such insolence, the Nereids asked Poseidon, god of the oceans, to punish Cassiopeia for her remarks. Poseidon agreed and summoned a sea monster to attack the ramparts of the kingdom’s capital and destroy the city.
Sages then informed Cepheus that it was possible to save his kingdom, but he would have to sacrifice his daughter, Andromeda. She was chained to a rock at the portals of the city, where she stoically waited for the sea monster to devour her. At this point in our tale the hero, Perseus, heard the terrible news and swooped down to Andromeda’s rescue on his winged horse, Pegasus. Perseus possessed a powerful weapon: the head of the Gorgon, Medusa, whose gaze would turn anyone to stone! The terrible sea monster didn’t stand a chance; Andromeda was saved along with Cepheus’ and Cassiopeia’s entire kingdom. The End. Roll credits…
Maybe you’re familiar with this storyline from a blockbuster movie you might have seen. But long before Hollywood, the characters in this mythological tale were immortalized by Greek astronomers in the form of constellations, and they are all easy to see: they appear next to each other in the autumn sky when the night is young. Cepheus, Cassiopeia, Perseus, Andromeda and Pegasus are all right there among the stars, close to the zenith. As for the sea monster, it’s represented by a large constellation known as Cetus, which is apart from the others and closer to the horizon.
For astronomers, these constellations contain a number of fascinating objects. The famous Andromeda Galaxy (M31 on our map) is irrefutably among the most notable : Though difficult to see from the city, under a dark sky it stands out as a small cloudlike oval, which is easily visible to the naked eye just above the star, Beta Andromedae. Between Cassiopeia and Perseus, there are two star clusters, one right next to the other, which are an extraordinary sight through binoculars or a small telescope: Individual stars are readily distinguishable in the Perseus Double Cluster. Also in the constellation of Perseus, there’s a star named Algol that’s different from the others: Its luminosity varies on a 2.87-day cycle. This fluctuation, which can be seen with the naked eye, is due to the presence of an orbiting companion star that regularly eclipses its central counterpart; Algol is, in fact, a binary system.
Regarding the planets
Three planets are easily visible in the starry sky this November. Though not very bright right now, Mars stands out against the background sky due to its orange colour. On the evening of November 25, the Red Planet will be easy to spot, when the lunar crescent appears 8 degrees to its right. Mars will remain in Sagittarius until the beginning of December.
For night owls, or for patient astronomers, Jupiter rises above the eastern horizon around midnight. Because of its brilliance, the giant planet is easy to spot among the stars of Leo, but if there’s any doubt, the gibbous moon will be near Jupiter during the night of November 13 to 14.
Mercury will also be visible at the beginning of the month: Look for it close to the east-southeast horizon, about an hour before sunrise. Mercury is currently much brighter than the star, Spica, which appears near the tiny planet during the first week of November.
Lastly… a couple of closing notes: The Sun will move from Libra into Scorpius on November 23, and then into Ophiuchus on the 30th. And on the night of Saturday November 1, to Sunday November 2, we return to Eastern Standard Time: Clocks are moved back one hour!