Perseus

Lore & Background

Perseus is a northern constellation named for the Greek hero who beheaded Medusa and rescued Andromeda. It covers 615 square degrees, ranking twenty-fourth among the 88 modern constellations, and is bordered by Andromeda and Cassiopeia to the north and west, Aries and Taurus to the south, and Auriga and Camelopardalis to the east. Its main asterism consists of 19 stars. The Milky Way’s galactic plane passes through it.

Its brightest star is the yellow-white supergiant Alpha Persei, also called Mirfak, at magnitude 1.79, which belongs to the Alpha Persei Cluster. The most famous star is Algol (Beta Persei), an eclipsing binary whose naked-eye variability inspired ominous legends. Other notable systems include X Persei, a binary with a neutron star, and GK Persei, a nova that reached magnitude 0.2 in 1901. The Double Cluster, two nearby open clusters, was known to ancient Chinese astronomers.

The constellation gives its name to the Perseus Cluster (Abell 426), a massive galaxy cluster 250 million light-years away, and hosts the radiant of the annual Perseids meteor shower. In Neo-Assyrian Babylonia, it was known as the Old Man constellation. Chinese astronomy placed four constellations within its area: the Celestial Boat, Swollen Waters, Great Trench, and a pile of corpses. In Polynesia, only the Society Islands named it, calling it Faa-iti, meaning "Little Valley."

Common Misconceptions (Editorial)

Some people think Perseus is a modern constellation, but it is actually one of the 48 ancient constellations listed by the 2nd-century astronomer Ptolemy. Another common misconception is that the star Algol is intrinsically variable, whereas it is actually an eclipsing binary.

Why It Matters (Editorial)

Perseus endures as a link between the night sky and one of Greek mythology’s most celebrated heroic journeys, from slaying Medusa to rescuing Andromeda. Its annual Perseid meteor shower, radiating from the constellation, keeps Perseus relevant not just for astronomers but for casual stargazers around the world, reminding us that ancient stories still align with living celestial events.

Reader's Guide

Perseus is a northern constellation linked to the Greek hero who slew Medusa and rescued Andromeda. It is one of the 48 ancient constellations cataloged by Ptolemy and is now among the 88 modern constellations. Its brightest star is the yellow-white supergiant Alpha Persei, also called Mirfak, which shines at magnitude 1.79 and is part of the Alpha Persei Cluster. The most famous star is Algol, or Beta Persei, an eclipsing binary whose noticeable variability inspired ominous legends.

Other notable systems include X Persei, a binary with a neutron star, and GK Persei, a nova that peaked at magnitude 0.2 in 1901. The constellation gives its name to the Perseus Cluster, a massive galaxy cluster 250 million light-years away, and hosts the radiant of the annual Perseids meteor shower. In Chinese astronomy, the area contains four constellations: the Celestial Boat, Swollen Waters, Great Trench, and a pile of corpses, with the Double Cluster holding special significance. In Polynesia, only the Society Islands recognized it, calling it Faa-iti, or "Little Valley." Early 19th-century star atlases sometimes depicted Perseus holding Medusa’s head as Perseus et Caput Medusae, but this usage did not become popular.

Did You Know?

• Perseus is also called Chrysopatros, meaning 'gold-fathered', because Zeus fathered him in the form of a shower of gold.
• The name Perseus may derive from Greek pérthein, meaning 'to waste, ravage, sack, destroy', suggesting a 'sacker of cities'.