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Credit & Copyright: Massimo Di Fusco
Explanation:
Found among the rich starfields of the Milky Way,
star
cluster NGC 7789 lies about 8,000 light-years away
toward the constellation Cassiopeia.
A late 18th century deep sky discovery of astronomer
Caroline
Lucretia Herschel,
the cluster is also known as Caroline's Rose.
Its
visual
appearance
in small telescopes, created by
the cluster's complex of stars and voids,
is suggestive of nested rose petals.
Now estimated to be 1.6 billion years young, the
galactic or open
cluster
of stars
also shows its age.
All the stars in the cluster were likely born
at the same time, but the brighter and more massive ones have more
rapidly exhausted the hydrogen fuel in their
cores.
These have evolved from
main sequence
stars like the Sun into the many red giant stars shown with a
yellowish cast in this color composite.
Using measured color and brightness,
astronomers can model the mass and hence the age of
the cluster stars just starting to "turn off" the main sequence
and become red giants.
Over 50 light-years across,
Caroline's Rose spans about
half a degree (the angular size of the Moon) near the center of
the sharp telescopic image.
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NASA Official: Jay Norris. Specific rights apply.
A service of: LHEA at NASA / GSFC
& Michigan Tech. U.
Based on Astronomy Picture
Of the Day
Publications with keywords: open cluster
Publications with words: open cluster
See also: