Robert's Quartet
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| Robert's Quartet | |
 |
|
| Observation data (Epoch J2000) | |
|---|---|
| Constellation(s) | Phoenix |
| Number of galaxies | 4 |
| Brightest member | NGC 92 |
| Other designations | |
| AM 0018-0485 | |
| See also: Galaxy groups and clusters, List of galaxy clusters | |
Robert's Quartet is a compact galaxy group approximately 160 million light-years away in the constellation Phoenix. It is a family of four very different galaxies in the process of colliding and merging. Its members are NGC 87, NGC 88, NGC 89 and NGC 92, discovered by John Herschel in the 1830s.
The quartet is one of the finest examples of compact groups of galaxies. Because such groups contain four to eight galaxies in a very small region, they are excellent laboratories for the study of galaxy interactions and their effects, in particular on the formation of stars. The quartet has a total visual magnitude of almost 13. The brightest member of the group has a magnitude of about 14. On the sky, the four galaxies are all within a circle of radius of 1.6 arcmin, corresponding to about 75,000 light-years. It was named by Halton Arp and Barry F. Madore, who compiled A Catalogue of Southern Peculiar Galaxies and Associations in 1987.
[edit] Members
| Name | Type | Distance from Sun (million ly) |
Magnitude |
|---|---|---|---|
| NGC 87 | IBm pec. | ~160 | +14.5 |
| NGC 88 | SB(rs)a pec. | ~160 | +15.21 |
| NGC 89 | SB0(s)a pec. | ~160 | +14.57 |
| NGC 92 | SAa pec. | ~160 | +14.29 |
[edit] External links
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