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BREAKING NEWS: Andromeda X--Andromeda's Newest Satellite Galaxy
The discovery of a new galaxy orbiting Andromeda gives a boost to the
leading theory of galaxy formation, say astronomers in Europe and the United States. The new galaxy, named Andromeda X, is the dimmest satellite galaxy ever seen around Andromeda. For the full story, including a never-before-published color image of the new galaxy, see http://KenCroswell.com/AndromedaX.html . Other recent stories: Most Stars Are Single (January 19, 2006): http://KenCroswell.com/MostStarsAreSingle.html . The Cosmic Origin of Carbon (January 11, 2006): http://KenCroswell.com/OriginOfCarbon.html . The Tenth Planet's First Anniversary (January 5, 2006): http://KenCroswell.com/TenthPlanetFirstAnniversary.html . Pulsar at the Galactic Center? (January 3, 2006): http://KenCroswell.com/G359.html . The Three Moons of Pluto (December 21, 2005): http://KenCroswell.com/PlutoMoons.html . The First Direct Distance to Andromeda (November 4, 2005): http://KenCroswell.com/AndromedaDistance.html . Correct email: MagnificentUniverse "at" yahoo "dot" com. |
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BREAKING NEWS: Andromeda X--Andromeda's Newest Satellite Galaxy
On Sun, 29 Jan 2006 20:34:19 -0800, "Magnificent Universe"
wrote: The discovery of a new galaxy orbiting Andromeda gives a boost to the leading theory of galaxy formation, say astronomers in Europe and the United States. The new galaxy, named Andromeda X, is the dimmest satellite galaxy ever seen around Andromeda. For the full story, including a never-before-published color image of the new galaxy, see http://KenCroswell.com/AndromedaX.html . I hate when they compare absolute magnitudes of stars to extended objects, it means NOTHING as far as visibility is concerned. Does anyone know what the dimmest absolute magnitude star is that can be seen with our current telescopes at the distance of the Andromeda galaxy? If stars need to be absolute magnitude -7 or something to be visible at all from Andromeda, it's no wonder there are possible invisilble companion galaxies there. -Rich |
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BREAKING NEWS: Andromeda X--Andromeda's Newest Satellite Galaxy
Rich wrote:
I hate when they compare absolute magnitudes of stars to extended objects, it means NOTHING as far as visibility is concerned. Does anyone know what the dimmest absolute magnitude star is that can be seen with our current telescopes at the distance of the Andromeda galaxy? If stars need to be absolute magnitude -7 or something to be visible at all from Andromeda, it's no wonder there are possible invisilble companion galaxies there. The distance modulus for M31 is about 24.5, give or take. So if you're talking about actually seeing it visually through an amateur-class telescope, even a large one, you probably are limited to stars that are absolute magnitude -7 or brighter. But for detection in images, we can obviously see stars much dimmer than that. With something like a Hubble Deep Field, you could see stars down to around sixth magnitude or so, absolute magnitude. Now, for purposes of detecting a galaxy, you need not detect the stars to see the galaxy, especially if the galaxy is far enough away that you don't resolve the individual stars. -- Brian Tung The Astronomy Corner at http://astro.isi.edu/ Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/ The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/ My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html |
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BREAKING NEWS: Andromeda X--Andromeda's Newest Satellite Galaxy
Brian Tung wrote: Now, for purposes of detecting a galaxy, you need not detect the stars to see the galaxy, especially if the galaxy is far enough away that you don't resolve the individual stars. In this particular case, of course, the problem is that the galaxy IS so close that we can and do resolve the individual stars. That's one of the reasons it's so hard to find dwarf galaxies in the Local Group: they only appear when one looks in big catalogs of stars for small regions of slightly higher stellar density .... Michael Richmond |
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