Astronomy Picture of the Day



The Big Dipper Cluster

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#85293 by @ 18.03.2006 00:00 - nach oben -
The Big Dipper Cluster


Explanation:

A well-known
asterism
in northern skies, The Big Dipper
is easy to recognize even
when
viewed
upside down.

Part of the larger constellation of
Ursa Major,
the bright
dipper stars above
are named
(left to right along the dipper)
Dubhe, Merak, Phecda, Megrez, Alioth, Mizar/Alcor, and Alkaid.

Of course,
stars in any given
constellation
are unlikely to be physically
related.

But surprisingly, most of the
big dipper stars do seem to
be headed in the same direction as they
plough through
space, a property they share with other stars spread out
over an even larger area across the sky.

Their
measured common motion
suggests that they all belong
to a loose, nearby
star cluster, thought to
be on average only
about 75 light-years away and up to 30 light-years across.

The cluster is more properly known as the
Ursa Major
Moving Group
.




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