description Abell 21 Overview
Abell 21, also known as the Medusa Nebula, is an ancient planetary nebula in the constellation Gemini. It was catalogued by astronomer George Abell in his 1966 survey of planetary nebulae. Located approximately 1,500 light-years from Earth, this stellar remnant exhibits a braided, filamentary structure resembling the snakes of Medusa from Greek mythology. Planetary nebulae like Abell 21 form when dying stars similar to our Sun shed their outer layers, exposing the hot stellar core that ionizes the surrounding gas, causing it to glow.
help Abell 21 FAQ
What kind of nebula is Abell 21?
Abell 21, commonly known as the Medusa Nebula, is an evolved planetary nebula located in the constellation Gemini. It was named for its striking resemblance to the Gorgon Medusa from Greek mythology.
Who catalogued the Medusa Nebula?
The nebula was catalogued by the American astronomer George Abell in the mid-20th century. Abell was responsible for identifying many planetary nebulae and galaxy clusters across the sky.
What does the Medusa Nebula look like through a telescope?
Visually, Abell 21 is quite faint and is distinguished by a complex network of filamentary arcs. Most amateur astronomers require a telescope with an OIII (doubly ionized oxygen) filter to clearly resolve the filaments of the nebula.
How was the Medusa Nebula formed?
Like other planetary nebulae, Abell 21 was formed when an aging red giant star shed its outer layers into space. The glowing filaments are the result of ultraviolet radiation from the dying central white dwarf star ionizing the expelled gas.
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