Cassiopeia: The Queen of the Night Sky

Cassiopeia is one of the most easily recognized constellations in the northern sky, thanks to its distinctive W or M shape formed by five bright stars. As a circumpolar constellation, it is visible year-round from most northern latitudes and serves as a reliable guide for finding Polaris and navigating the sky. Locate it instantly by pointing your phone upward with StarGlobe.

How to Find Cassiopeia

Cassiopeia sits on the opposite side of Polaris from the Big Dipper in Ursa Major. When the Big Dipper is low on the northern horizon, Cassiopeia is high overhead, and vice versa. This makes the two constellations complementary tools for finding the North Star.

The five main stars form a zigzag pattern that resembles a W when the constellation is high in the sky and an M when it is near the horizon. This shape is compact and bright enough to be seen even under moderate light pollution, making Cassiopeia one of the best constellations for urban stargazers.

To use Cassiopeia to find Polaris, locate the deeper of the two V shapes in the W pattern. The star at the bottom of this V, Gamma Cassiopeiae, points roughly toward the North Star when you extend the line about the same distance again.

The Stars of Cassiopeia

The five main stars of Cassiopeia, from west to east in the W pattern, are Caph, Schedar, Gamma Cassiopeiae (Navi), Ruchbah, and Segin. Schedar, an orange giant at magnitude 2.2, is typically the brightest, though the constellation's stars are all within a magnitude of each other, contributing to its balanced and recognizable shape.

Gamma Cassiopeiae, the central star of the W, is a peculiar variable star. It is a hot blue star that spins so rapidly it periodically throws off rings of gas from its equator, causing unpredictable brightness fluctuations. It has varied between magnitude 1.6 and 3.0 over the past century. Astronaut Gus Grissom gave it the informal name Navi, which is his middle name Ivan spelled backward.

Caph, at the western end of the W, is a yellow-white giant that was once used as a standard star for photometric calibration. Ruchbah is an eclipsing binary star whose brightness dips slightly every two days as the fainter component passes in front of the brighter one.

Deep Sky Objects

Cassiopeia lies along the Milky Way, making it rich in star clusters and nebulae. Two open clusters stand out for binocular observers. NGC 457, sometimes called the Owl Cluster or E.T. Cluster, features a striking pattern of stars that resembles a stick figure with outstretched arms. NGC 663 is a large, bright cluster visible in binoculars as a hazy patch of light.

M52 is another prominent open cluster in Cassiopeia, containing roughly 200 stars at a distance of about 5,000 light-years. M103, near Ruchbah, is one of the more distant Messier open clusters at about 8,500 light-years away.

The constellation also contains the remnant of Tycho's Supernova, which appeared in 1572. Danish astronomer Tycho Brahe observed this "new star" that briefly outshone Venus, and his careful measurements helped challenge the ancient idea that the heavens were unchangeable. The remnant is now visible as a faint expanding shell of gas detectable at radio and X-ray wavelengths.

Mythology and Cultural Background

In Greek mythology, Cassiopeia was the queen of Aethiopia and wife of King Cepheus. She boasted that she (or her daughter Andromeda) was more beautiful than the Nereids, the sea nymphs. This angered Poseidon, who sent a sea monster to ravage the coast. To appease the god, Andromeda was chained to a rock as a sacrifice but was rescued by Perseus.

As punishment for her vanity, Cassiopeia was placed in the sky tied to her throne, condemned to circle the pole and spend half the night hanging upside down. The W shape of the constellation has been interpreted as her seated figure on the throne.

In Chinese astronomy, the stars of Cassiopeia were part of several different asterisms associated with the celestial palace. In some Pacific Island traditions, the W shape represents a fishing net or the wing of a great bird.

Best Time to Observe

Cassiopeia is circumpolar from latitudes above about 35 degrees north, meaning it never sets. The constellation is highest in the sky during autumn evenings, from September through November, when it passes nearly overhead for observers in the northern United States and Europe. This is when its star clusters and Milky Way backdrop are best positioned for observation.

During spring evenings, Cassiopeia rides low along the northern horizon, making it less impressive but still visible. From the Southern Hemisphere, Cassiopeia is visible only from tropical latitudes and remains very low in the northern sky.

Neighboring Constellations

Cassiopeia is surrounded by constellations connected to its mythological story. Perseus lies to the southeast, Andromeda to the south, and Cepheus borders it to the west and north. This family of constellations stretches across the autumn sky, telling one of the most complete stories in celestial mythology.

Cygnus lies further to the west along the Milky Way, and Camelopardalis fills the space between Cassiopeia and Ursa Minor. Trace all these connections in real time with StarGlobe.

Quick Facts

Cassiopeia spans 598 square degrees, ranking 25th in size. It contains two Messier objects (M52 and M103) and numerous NGC star clusters. The constellation sits within the Milky Way band, providing a rich field for binocular scanning. Its right ascension runs from roughly 22h 57m to 3h 41m, and its declination spans from about +46 to +77 degrees. Track the Queen's nightly rotation with StarGlobe.