Astronomy Picture of the Day



Andromeda Island Universe

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zorg.ch
#82934 by @ 23.12.2005 00:00 - nach oben -
Andromeda Island Universe


Explanation:

The most distant object easily visible to the unaided eye is
M31,
the great
Andromeda Galaxy
some two million light-years away.

But without a telescope, even this immense spiral galaxy - spanning over
200,000 light years - appears as a
faint, nebulous cloud in the
constellation
Andromeda
.

In contrast, a bright yellow nucleus, dark winding dust lanes,
gorgeous blue spiral arms and star clusters are recorded in this
stunning
telescopic
digital mosaic
with a cumulative exposure of over 90 hours.

While even casual
skygazers
are now inspired by the knowledge that there are
many distant galaxies like M31, astronomers
seriously debated
this fundamental concept only 80 years ago.

Were these "spiral nebulae" simply outlying components of our own
Milky Way Galaxy or were they instead "island universes" -- distant
systems of stars comparable to the Milky Way itself?

This question was central to the famous
Shapley-Curtis
debate
of 1920, which was later resolved by
observations of M31
in favor of Andromeda,
island
universe
.




Credit & Copyright
zorg.ch
#82935 by @ 23.12.2005 00:32 - nach oben -
hei bärbel, kennsch dä URS scho?