Explanation:
Still gracing northern skies, a fading Comet Holmes lies at the top
edge of this
colorful
skyview, recorded on March 4.
The reddish emission nebula below it is NGC 1499, also known as
the California Nebula
for its resemblance to the outline of the state
on the US west coast.
Of course, the two cosmic clouds by chance lie along nearly the same
line-of-sight and so only appear to be close together and of similar
size.
The California Nebula is actually about 100 light-years long and 1,500
light-years away, drifting through the Orion Arm of our spiral Milky Way
Galaxy.
Comet Holmes is about 20
light-seconds in diameter, sweeping
through our solar system a mere 25
light-minutes away,
beyond the orbit of Mars.
The molecules of the comet's gaseous
comafluoresce in sunlight.
The California Nebula's glow is characteristic of hydrogen atoms
recombining with
long lost electrons, originally
stripped away
(ionized) by ultraviolet starlight.
Providing the energetic starlight is Xi
Persei,
the prominent star below the nebula.
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