The Andromeda Galaxy
/ sciencereason ... "The Andromeda Galaxy" with Jane Houston Jones at NASA's Jet Propulsion Laboratory in Pasadena, California.
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The Andromeda Galaxy (also known as Messier 31, M31, or NGC 224) is a spiral galaxy approximately 2,500,000 light-years away in the constellation Andromeda. It is the nearest spiral galaxy to our own, the Milky Way. As it is visible as a faint smudge on a moonless night, it is one of the farthest objects visible to the naked eye, and can be seen even from urban areas with binoculars.
It is named after the princess Andromeda (Greek: Ανδρομέδη Andromédē) in Greek mythology. Andromeda is the largest galaxy of the Local Group, which consists of the Andromeda Galaxy, the Milky Way Galaxy, the Triangulum Galaxy, and about 30 other smaller galaxies.
Although the largest, Andromeda may not be the most massive, as recent findings suggest that the Milky Way contains more dark matter and may be the most massive in the grouping.
The 2006 observations by the Spitzer Space Telescope revealed that M31 contains one trillion stars, several times more than the number of stars in our own galaxy, which is estimated to be c. 200-400 billion.
While the 2006 estimates put the mass of the Milky Way to be ~80% of the mass of Andromeda, which is estimated to be 7.1 × 1011 solar masses, a 2009 study concluded that Andromeda and the Milky Way are about equal in mass.
At an apparent magnitude of 3.4, the Andromeda Galaxy is notable for being one of the brightest Messier objects, making it easily visible to the naked eye even when viewed from areas with moderate light pollution.
Although it appears more than six times as wide as the full moon when photographed through a larger telescope, only the brighter central region is visible with the naked eye.
• http://en.wikipedia.org/wiki/Andromed...
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When you look up at the sky youll easily see solar system objects like Jupiter and the moon. You can also see stars, clumps and knots of nebulosity in our Milky Way Galaxy. But did you know you can actually see another galaxy with your own eyes, even without a telescope?
The Andromeda Galaxy is the most distant easily visible object in the sky, and its also the largest and closest spiral galaxy that we can see. Its visible even under moderate light polluted skies as a misty patch. Through binoculars and telescopes more and more detail is revealed to the observer.
Astronomers have observed the Andromeda galaxy for over a thousand years. Persian astronomer Al-Sufi was the first to record and sketch his observations of what he called the little cloud. In 964 he published this observation and many others in his Book of Fixed Stars.
Since the 16th century many astronomers rediscovered the Andromeda Galaxy unaware of the earlier sightings. Simon Marius first viewed the galaxy through a telescope in 1612.
It is also known as M-31 on Charles Messiers list of objects, although he was aware of some earlier sightings. In 1887 the first photograph revealed the spiral structure of the Andromeda Galaxy, which was then known as a nebula. And in the early 20th century Edwin Hubbles study of Andromeda nebula proved the nebula was not just a star cluster in our own Milky Way, but a separate galaxy.
NASA's Swift satellite recently acquired the highest-resolution view of a neighboring spiral galaxy ever attained in ultraviolet wavelengths. Swift revealed about 20,000 ultraviolet sources in the Andromeda Galaxy, especially hot, young stars and dense star clusters. NASAs Spitzer Space Telescope, Galaxy Evolution Explorer and Chandra X-Ray Observatory also observed the Andromeda Galaxy in infrared, ultraviolet and X-ray wavelengths.
• http://www.nasa.gov/multimedia/podcas...
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