All About The Cassiopeia Constellation
While Cassiopeia may not be among the most widely-known constellations, it might be one of the few that truly lives up to its namesake. Through their long histories, we assume constellations reside in the night sky as inarguable depictions of their collected stars—but sometimes constellations aren’t all that reflective of the images we ascribe to them.
Take Ursa Major, for instance. While it is said to be in the likeness of a ‘bear’, someone viewing it without that specified prior knowledge may be more inclined to view it as a ‘dog’ or ‘horse’ or some other four-legged animal—or not an animal at all. Constellations are the stars an astronomer chose to connect, and Cassiopeia is no exception to this rule. Said to be in the shape of a ‘beautiful queen’, one might be hard-pressed to make out that likeness. However, despite this, Cassiopeia is still home to unrivaled beauty and wonder—perhaps not in the figure it represents, but in the contents of its space.
Cassiopeia is another example of the original forty-eight constellations listed out by the Greek-Egyptian astronomer Ptolemy, and it remains one of the eighty-eight recognized constellations today. Its namesake was derived from the myth of Cassiopeia, who was said to have been a queen of ancient Aethiopia (a place roughly aligning with the modern region of Ethiopia), an ancient Greek territory.
As the story goes, Cassiopeia was said to have been a vain and arrogant queen—going so far as to claim that the beauty of herself and her daughter, Andromeda, was far greater than that of the Nereids, a group of sea-nymphs. The boast enraged the sea-god Poseidon, who sought to punish the kingdom of Aethiopia for Cassiopeia’s transgression. And, by the council of a wise oracle, Cassiopeia thought she could save herself and her kingdom by sacrificing Andromeda to the sea-monster Cetus. By chaining her daughter to a rock by the sea, and leaving her for dead, Cassiopeia believed she had saved herself from Poseidon’s wrath. This is, however, where the myth of Perseus intersects—as he would then slay the monster Cetus, and take Andromeda as his own wife.
While Perseus might have inadvertently saved the kingdom of Aethiopia, Poseidon still desired revenge against Cassiopeia—not only for her slight against the Nereids but also for her cruel actions towards Andromeda. For this reason, he cast her into the sky, where she would sit for eternity, chained to a throne to mimic Andromeda's cruel torture by the sea.
Because of this myth, the constellation Cassiopeia is often depicted as a woman sitting on a throne. While other renditions do exist, such as a woman holding a mirror in reflection of Cassiopeia's vanity, or holding a palm branch, an ancient symbol of peace or victory—they are ancillary to the primary tale.
By Till Credner - Own work: AlltheSky.com
Beauty in Scientific Discovery
Though Cassiopeia’s claims of beauty may have been hubris in the myth, the constellation that bears her name has plenty to admire. The constellation inhabits an incredibly rich region of space, with many interesting and vibrant phenomena to observe. For example, within Cassiopeia is the ‘W’ asterism, comprising the five brightest stars of the constellation that roughly form the shape of that letter and are easily visible to the naked eye.
Among these five, Alpha Cassiopeiae is the brightest of the group, and is also known by the name Schedar, derived from the Arabic word şadr, meaning breast. This is in reference to the star's close position to the heart of Cassiopeia, and serves as another example of the boundary-crossing nature of both astronomy and ancient myths.
The second brightest star, Beta Cassiopeiae, was thought to be a contender for brightest star in the constellation for some time. Beta Cassiopeia is known also as Caph, coming from the Arabic word kaf, meaning palm. This name is actually the last remaining remnant of a pre-Islamic Arabic asterism known as al-Kaff al-Khadib or, ‘the stained hand—a reference to a hand covered in henna tattoos.
The star itself is a massive (three-times the size of our sun) variable star, meaning its luminosity fluctuates. This is due to the star's incredibly fast rotation, which forces it into an oblate-spheroid shape—defined as flattened at the poles and bulging out at the sides.
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Deep-Sky and Bright Lights
While the stars of Cassiopeia are fascinating to discuss, the true beauty lies in the deep-sky objects hidden in its depths. Two supernova remnants can be found there, the remains of remarkably massive stellar deaths which have the ability to wipe whole star systems from existence.
One is known as Tycho's Supernova (SN 1572/ B Cassiopeiae) remnant, a reference to the astronomer who studied the supernova itself in 1572. The supernova, then called a ‘new star’, represented a massive upheaval in astronomy at the time—as early astronomers struggled to explain how a star could suddenly appear in the sky, before beginning to fade just as quickly.
The second supernova remnant is Cassiopeia A. Though its light would have reached Earth in the late 1600’s, there are no contemporary records—so it failed to make the same waves as its far-brighter predecessor. Still, Cassiopeia A is interesting in that it can be viewed with an armature telescope, and is the greatest source of radio waves outside of the solar system.
Other deep space objects within Cassiopeia include a wide-range of open clusters, or loose associations of thousands of stars which rotate a common point—as well as a variety of galaxies and nebulae. That said, perhaps the most fascinating of these objects is the IC 10 Galaxy.
IC 10 is the only starburst galaxy of our local group (the group of galaxies the Milky Way orbits with) and is known for their massive factory-like methods of stellar creation. A starburst galaxy forms stars at such an impressive rate, that they will burn out well before the end of the universe. This makes them one of the less-permanent objects observable, and worth exploring, as there will come a day where all the starburst galaxies have long since gone extinct—but the universe lingers on.
Where to Find Cassiopeia in the Sky
Due to the brightness of its stars, Cassiopeia can be easily located in the northern sky, and is visible year- round. It is neighbored by constellations fitting of its mythic ancestry, as Andromeda and Perseus are visible nearby—along with the constellation dedicated to Cassiopea’s husband, Cepheus.
All-together in this local region of space, where all those constellations are visible, nearly the entire tale of Cassiopeia’s downfall is told—and it presents a wonderful opportunity to combine the brilliance of stargazing with the timeless traditions of human storytelling.