Talk:Virgo Supercluster
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[edit] Apparent size criterion
What is considered "large" apparent size? Ardric47 02:17, 20 March 2006 (UTC)
- There's some arbitrary cut-off in terms of angular size: 100 arcseconds. I modelled our list after the one in http://www.atlasoftheuniverse.com/galaclus.html, which also uses this cut-off. It keeps the listing from including heavy but very distant clusters that have been relatively poorly observed. -- Xerxes 01:35, 22 March 2006 (UTC)
[edit] Great attractor
"The local (Coma-Virgo), Perseus-Piscus, Hydra-Centaurus, Orphiuchus, Vela, and a number of other superclusters are observed to move towards the Great Attractor as speeds of greater than 600,000 km per second," Isn't this about 3 times the speed of light?
- It's twice the speed of light. Although it's possible for different parts of the universe to be moving away from each other at faster-than-light speeds (by some definitions) due to the expansion of space, I'm suspicious about that happening so close to us. Ardric47 00:17, 22 March 2006 (UTC)
- You don't want to know. Or maybe you do. This might possibly be harnessed somehow for future spaceships. This is better than an Scramjet!--Image:Nuvola apps kcmmemory.pngMac Lover Talk 17:15, 10 August 2006 (UTC)
[edit] Group/cluster list
The group/cluster member list is a mess. Moreover, this list gets really messy when considering the difficulty in identifying whether galaxies are parts of groups (see the Sombrero Galaxy under "Environment") and the difficulty in distinguishing whether galaxies are subdivided into small groups or combined together into large groups (see my revisions to the M101 Group article and the section labelled "Nearby groups"). This section could be misleading or confusing, and its accuracy will always be questionable, so I am removing the section. GeorgeJBendo 21:21, 28 October 2006 (UTC)
[edit] Image
There were complaints that Image:Local_supercluster.jpg (the image on the right) was unreadable because it used km, so I made one using light years instead: Image:Local_supercluster-ly.jpg. Hairy Dude 01:04, 7 July 2007 (UTC)
- Do you have references for all of the distance measurements in that figure? For that matter, are those terms for various clusters of galaxies actually in use (i.e. have those terms been used in a scientific journal article published in the past 10 years)? If the answer to either of these questions is no, then maybe the picture should not be used. Dr. Submillimeter 18:30, 7 July 2007 (UTC)
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- The orgiginal image created by nasa had distance measurements in it in km. Performing a simple unit conversion is allowed. McKay 16:25, 10 July 2007 (UTC)
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- A NASA public outreach website may not be the best source of information for this data. I would contend, for example, that some of these designations are not in use. For example, a search for "Draco Group" in professional astronomy journals with the ADS Abstract Service turns up no articles that use the term. I would also like to see references from journal articles for the distances. The distance to Messier 81 and Messier 82 given by [1], which are part of the M81 Group, is 11.5-11.8 Mly, not 11 Mly as shown in this figure. Similarly, the distance to Messier 51 in the M51 Group is given by [2] is 23 Mly, not the 31 Mly shown in this figure. I sincerely recommend deleting it, as it is inaccurate. Dr. Submillimeter 17:04, 10 July 2007 (UTC)
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