The Medusa Nebula
From NASA’s Astronomy Picture of the
Day
Braided, 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 along the southern border of 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. An unrelated, bright, foreground star is
near center in this close-up,
telescopic view, while the Medusa's transforming central star is actually
the dimmer star below center and toward the right-hand part of the frame.
The Medusa Nebula is
estimated to be over 4 light-years across.
