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NASA Astronomy Picture of the Day

🌌 NASA Astronomy Picture of the Day

Nebula Nova Cygni Turns On

Date: 1996-12-16

Nebula Nova Cygni Turns On

View HD Image

Explanation:

Old photographs show no evidence of the above
nebula. In 1992, a white dwarf star in Cygnus
blew off its outer layers in a classical nova explosion:
an event called Nova Cygni 1992.
Light flooded the local interstellar neighborhood, illuminated
this existing gas cloud,
excited the existing hydrogen,
and hence caused the red emission. The only gas actually expelled
by the nova
can be seen as a small red ball just above the photograph's center.
Eventually, light from the nova shell
will fade, and this nebula will again become invisible!