Credit & Copyright: Guenter Kerschhuber
Explanation:
Centered in a well-composed celestial still life, pretty,
blue vdB 9 is the 9th object in
Sidney van den Bergh's 1966
catalog
of reflection nebulae.
It shares this telescopic field of view,
about twice the size of a full moon on the sky,
with stars and dark, obscuring dust clouds
in the northerly constellation Cassiopeia.
Cosmic dust is preferentially
reflecting blue starlight from embedded, hot star
SU Cassiopeiae,
giving vdB 9 the characteristic bluish tint
associated with a classical reflection nebula.
SU Cas is a Cepheid variable star, though even at its brightest it is
just too faint to be seen with the unaided eye.
Still Cepheids play an important role in determining distances in our
galaxy
and beyond.
At the star's well-known distance of 1,540 light-years,
this
cosmic canvas would be about 24 light-years across.
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reflection nebula - otrazhatel'nye tumannosti
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