Explanation: Braided and serpentine filaments of glowing gas suggest this nebula's popular name, The Medusa Nebula. Also known as Abell 21, this Medusa is an old planetary nebula some 1,500 light-years away in the constellation Gemini. Like its mythological namesake, the nebula is associated with a dramatic transformation. The planetary nebula phase represents a final stage in the evolution of low mass stars like the sun as they transform themselves from red giants to hot white dwarf stars and in the process shrug off their outer layers. Ultraviolet radiation from the hot star powers the nebular glow. The Medusa's transforming star is the faint one near the center of the overall bright crescent shape. In this deep telescopic view, fainter filaments clearly extend below and to the left. The Medusa Nebula is estimated to be over 4 light-years across.
The Medusa Nebula
AI-generated summary
The Medusa Nebula, also known as Abell 21, is an old planetary nebula located about 1,500 light-years away in the constellation Gemini. Its name comes from the braided and serpentine filaments of glowing gas that resemble the mythological Medusa. This nebula represents a final stage in the evolution of low mass stars, transitioning from red giants to hot white dwarf stars while shedding their outer layers. The nebula's glow is powered by ultraviolet radiation from a faint star at its center. The Medusa Nebula spans over 4 light-years across.