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Credit & Copyright: Amir H. Abolfath
(TWAN)
Explanation:
How far can you see?
The most distant object easily visible to the unaided eye is M31, the great
Andromeda Galaxy, over two million
light-years away.
Without a telescope, even this immense
spiral galaxy
appears as an unremarkable, faint,
nebulous cloud in the
constellation Andromeda.
But a bright yellow nucleus, dark winding dust lanes, luminous blue spiral arms,
and bright red emission nebulas are recorded in
this stunning six-hour telescopic digital mosaic of our closest major galactic
neighbor.
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
100 years ago.
Were these "spiral nebulae" simply outlying gas clouds in our own
Milky Way Galaxy or were they "island universes" -- distant galaxies 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 favoring Andromeda being just like our
Milky Way Galaxy -- a conclusion making
the rest of the universe
much more vast than many had ever imagined.
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NASA Web Site Statements, Warnings, and Disclaimers
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: Andromeda galaxy - M 31
Publications with words: Andromeda galaxy - M 31
See also:
- NGC 206 and the Star Clouds of Andromeda
- APOD: 2024 September 8 Á M31: The Andromeda Galaxy
- APOD: 2023 November 13 Á Andromeda over the Alps
- The Once and Future Stars of Andromeda
- APOD: 2023 August 23 Á The Meteor and the Galaxy
- APOD: 2023 March 22 Á M31: The Andromeda Galaxy
- APOD: 2023 January 17 Á Unexpected Clouds Toward the Andromeda Galaxy