|
|
|
||||||||
|
PJM's Astronomy Gallery
CCD ASTROPHOTOGRAPHY IMAGE OF THE MONTH
features
M51 - A Close Encounter of the First or Multiple Kind ?
|
||||||||||||||||||||||||||||||||
 |
||||||||||||||||||||||||||||||||
|
Homepage &
Image Gallery
|
||||||||||||||||||||||||||||||||
 |
||||||||||||||||||||||||||||||||
|
M51, Whirlpool Galaxy ( NGC 5194 ) in Canes Venatici. 200 mm f/4 Schmidt-Newtonian images at prime focus on 26 May 1999.
LEFT: Combined R:G:B:L images of 12:15:12:5 minutes exposure. Field of view is 9 by 9 arcmin.
BELOW: 8 minutes exposure. Field of view is 21 by 15 arcmin.
|
||||||||||||||||||||||||||||||||
 |
||||||||||||||||||||||||||||||||
|
Data: Messier No. 51 (NGC 5194)
Location: Canes Venatici (R.A. 13:30:02 Dec. +47:11:02 )
Distance: 37 million light years
|
||||||||||||||||||||||||||||||||
|
Magnitude: 8.4
Size: 9 by 7.5 arcmin.
|
||||||||||||||||||||||||||||||||
|
Information on M51 and other useful background to this news has been sourced at SEDS.
M51, Whirlpool Galaxy, is classified as a Sc type spiral galaxy (for classification types and examples see Galaxies ), and is a favourite target of many amateur astronomers. Although discovered by Messier in 1773, the spiral structure was not recognised until 1845 by Lord Rosse with his 72 inch speculum metal reflector. As reported by K Hewitt-White in Sky and Telescope (Vol. 105, (5), 116, 2003), the idea that faint nebulae might be distant star systems was widespread at the time. However, the spiral structure of M51, though not resolved into individual star makeup, added considerable weight to this idea.
|
||||||||||||||||||||||||||||||||
|
It is clearly evident from the above image that M51 is interacting with another galaxy, identified as NGC 5195, at it's northern edge. A connecting bridge can be identified. The bluish appearance of M51 spiral arms, due to young and hot Population I type stars, contrasts with the older, yellow Population II type stars of NGC 5195. It is not readily evident, however, whether the galaxies have seen a single encounter or multiple.
|
||||||||||||||||||||||||||||||||
|
Joshua Roth in Sky and Telescope ( Vol. 105,(5), 19, 2003 ), reports on work (Astrophysical Journal, Jan., 2003) by P Durell and colleagues (Pennsylvania State University) to resolve the above dilemma. Their study involved the measurement of the radial velocity of planetary nebulae in the outskirts of M51 and near the interaction zone.The radial velocities were sharply delineated into discrete families rather than "smeared", which would favour multiple interactions. Their study thus favours a single encounter. NGC 5195 is reputed to be "behind" M51 and receding fast from the interaction modelled as occuring some 280 million years ago.
|
||||||||||||||||||||||||||||||||
|
Image of the Month Articles
|
||||||||||||||||||||||||||||||||
|
References and Further Reading
|
||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||
 |
||||||||||||||||||||||||||||||||
|
|
||||||||||||||||||||||||||||||||
| page created with Easy Designer |