wvreeven
August 29th, 2023, 09:39 AM
Robert's Quartet, Phoenix Group, SCG2 0018-4854
Group of Galaxies
Phoenix
RA: 00 21 23.0
DEC: -48 38 20
Mag: 13.91 (B)
Arguably the best know list of galaxy groups probably is the Hickson Compact Groups list. But there are many others, including the SCG (Southern Compact Group) list, where the 2 refers to the second paper (https://simbad.cds.unistra.fr/simbad/sim-ref?bibcode=2002AJ....124.2471I) that was released regarding that topic. One of the groups in this list is Robert's Quartet, also known as the Phoenix Group. The group contains four galaxies: NGC 87, NGC 88, NGC 89 and NGC 92, which were discovered by John Herschel on 30 September 1834.
5209
VLT image (credit: ESO).
In 1987 Halton Arp and Barry Madore compiled A Catalogue of Southern Peculiar Galaxies and Associations. Robert Freedman helped generate many updated positions for the catalogue so Arp and Madore named the group Robert's Quartet in honor of his work.
Visually the group is very tight. The four galaxies lie within a circle with a diameter of 3.2' which, at the distance of the group, corresponds to about 150,000 lightyears or about 1.5 times the size of our own Milky Way. Mutual interactions have malformed all four galaxies. Unfortunately, I didn't see much of that and I wonder what you make of it. My observations read:
NGC 87: At 320x oval with a stellar nucleus.
NGC 88: At 320x round and small with a stellar core.
NGC 89: At 320x oval about 2:1 with a central brighter region.
NGC 92: At 320x oval about 2:1 with a central brighter part. Occasionally an extension about the size of the major axis of the galaxy is visible.
As always,
"Give it a go and let us know!
Good luck and great viewing!"
Group of Galaxies
Phoenix
RA: 00 21 23.0
DEC: -48 38 20
Mag: 13.91 (B)
Arguably the best know list of galaxy groups probably is the Hickson Compact Groups list. But there are many others, including the SCG (Southern Compact Group) list, where the 2 refers to the second paper (https://simbad.cds.unistra.fr/simbad/sim-ref?bibcode=2002AJ....124.2471I) that was released regarding that topic. One of the groups in this list is Robert's Quartet, also known as the Phoenix Group. The group contains four galaxies: NGC 87, NGC 88, NGC 89 and NGC 92, which were discovered by John Herschel on 30 September 1834.
5209
VLT image (credit: ESO).
In 1987 Halton Arp and Barry Madore compiled A Catalogue of Southern Peculiar Galaxies and Associations. Robert Freedman helped generate many updated positions for the catalogue so Arp and Madore named the group Robert's Quartet in honor of his work.
Visually the group is very tight. The four galaxies lie within a circle with a diameter of 3.2' which, at the distance of the group, corresponds to about 150,000 lightyears or about 1.5 times the size of our own Milky Way. Mutual interactions have malformed all four galaxies. Unfortunately, I didn't see much of that and I wonder what you make of it. My observations read:
NGC 87: At 320x oval with a stellar nucleus.
NGC 88: At 320x round and small with a stellar core.
NGC 89: At 320x oval about 2:1 with a central brighter region.
NGC 92: At 320x oval about 2:1 with a central brighter part. Occasionally an extension about the size of the major axis of the galaxy is visible.
As always,
"Give it a go and let us know!
Good luck and great viewing!"