NGC 7331 Group
| NGC 7331 Group | |
|---|---|
,_Unannotated_Version.jpg) NGC 7331, along with NGC 7335, 7336, 7337 and 7340 | |
| Observation data (Epoch J2000) | |
| Constellation | Pegasus |
| Right ascension | 22h 37m |
| Declination | +34° 25′ |
| Brightest member | NGC 7331 |
| Number of galaxies | 5 |
| Parent structure | Perseus–Pisces Supercluster |
| Other designations | |
| NGC 7331 Group, LGG 459, Deer Lick Group, Holm 795 | |
Description
[edit]The NGC 7331 Group is a visual grouping of galaxies located in the constellation Pegasus.[1] The system is anchored by its largest member, NGC 7331, which lies approximately 40 million light-years (12.3 Mpc) from Earth.[1]
Apparent directly northeast of NGC 7331 are four smaller and much fainter galaxies, known as "the fleas":[1]
- NGC 7335: A lenticular galaxy located 290 million light-years (89 Mpc) away
- NGC 7336: A spiral galaxy located 370 million light-years (113 Mpc) away
- NGC 7337: A barred spiral galaxy located 300 million light-years (92 Mpc) away
- NGC 7340: An elliptical galaxy located 290 million light-years (89 Mpc) away
Physical vs. Visual Association
[edit]Although historical catalogs grouped these objects together due to their visual close proximity , spectroscopic measurements from the NASA/IPAC Extragalactic Database (NED) confirm that the group is an optical grouping caused by line-of-sight alignment rather than a gravitationally bound cluster.[2]
While NGC 7331 sits in the foreground at a heliocentric radial velocity of 816 km/s (redshift 0.002722), the four background companion galaxies exhibit recessional velocities between 6,200 km/s and 8,800 km/s (redshift 0.021 to 0.029 Z).[2] As a result, the four companion galaxies sit at distances ranging from 290 to 370 million light-years.[1]
The true physical group bound to NGC 7331 consists of several satellite dwarf galaxies at matching distances, and NGC 7320 (which visually overlaps Stephan's Quintet), UGC 1206), and UGC 12160.[3]
Nomenclature and History
[edit]NGC 7331 was discovered by astronomer William Herschel on September 6, 1784.[1] Swedish astronomer Erik Holmberg cataloged the visual system as Holm 795 in his 1937 study of multiple galaxies.[4]
The popular informal name "Deer Lick Group" was coined in the 1980s by American amateur astronomer Tom Lorenzin to commemorate an exceptional viewing session at the Deerlick Gap Overlook along the Blue Ridge Parkway in North Carolina, where he observed NGC 7331 along with its faint background companion galaxies.[1]
See also
[edit]External links
[edit]- "NAME NGC 7331 Group". SIMBAD. Centre de données astronomiques de Strasbourg.
- ADS: The NGC 7331 Group, a Stable Group of Galaxies Projected on Stephan's Quartet
- Nemiroff, R.; Bonnell, J., eds. (12 July 2008). "NGC 7331 and Beyond". Astronomy Picture of the Day. NASA.
- NGC 7331 Group on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images
- 3–10 October 2008: Andromeda Galaxy (M31), Gamma Andromedae, and the NGC 7331 Group on Astronomy.com blog Archived 6 October 2008 at the Wayback Machine
- NGC 7331 Group at de-regt.com
References
[edit]- 1 2 3 4 5 6 Kruesi, Liz (21 March 2022). "101 Must-See Cosmic Objects: NGC 7331". Astronomy Magazine. Retrieved 22 July 2026.
- 1 2 "NASA/IPAC Extragalactic Database Results for NGC 7331". NASA/IPAC Extragalactic Database. Retrieved 22 July 2026.
- ↑ Garcia, A. M. (July 1993). "General study of group membership. II. Determination of nearby groups". Astronomy and Astrophysics Supplement Series. 100: 47–90. Bibcode:1993A&AS..100...47G.
- ↑ Holmberg, Erik (1937). "A Study of Double and Multiple Galaxies Together with Inquiries into some General Metagalactic Problems". Annals of the Observatory of Lund. 6: 1–173. Bibcode:1937AnLun...6....1H.