Global InformationNGC 922 information
| NGC 922 | |
|---|---|
 Hubble view of NGC 922 | |
| Observation data (J2000 epoch) | |
| Constellation | Fornax |
| Right ascension | 02h 25m 04.400s[1] |
| Declination | −24° 07′ 17.46″[1] |
| Redshift | 0.010314±0.000020[2] |
| Heliocentric radial velocity | 3,075 km/s[3] |
| Distance | 142 Mly (43.4 Mpc)[4] |
| Apparent magnitude (V) | 12.21[5] |
| Characteristics | |
| Type | SB(s)cd pec[2] |
| Mass | 5.47×109 M☉[6] M☉ |
| Apparent size (V) | 2′.0 × 1′.7[7] |
| Other designations | |
| GSC 06433-00965, MCG-04-06-037, UGCA 30, AM 0222-250, IRAS 02228-2500, PSCz Q02228-2500, [WDW2002] HIPASS J0224-24, DUGRS 478-001, IRAS F02228-2500, RR95 53a, ESO 478-28, ISG 10, SGC 022248-2500.9, ESO-LV 478-0280, LEDA 9172, SINGG HIPASS J0224-24 S1[5] | |
NGC 922 is a peculiar galaxy in the southern constellation of Fornax, located at a distance of 142 Mly[4] from the Milky Way. It is one of the nearest known collisional galaxies.[8] This object was described by the Herschels as "considerably faint, pretty large, round, gradually pretty much brighter middle."[7] The general form is described by the morphological classification of SB(s)cd pec,[2] which indicates a peculiar (pec) barred spiral galaxy (SB) with no inner ring system around the bar (s) and loosely-wound spiral arms (cd).
This object was originally described as a dust-obscured grand-design galaxy – a term used to indicate a type of spiral galaxy with prominent and well-defined spiral arms. However, observation of its features suggests it has undergone a merger with a gas-rich dwarf galaxy.[9] This has resulted in a distinctive C-shaped ring of H-alpha emission.[10] About 104 kpc away from NGC 922, there is a dwarf galaxy called S2 that was once thought to have been responsible for NGC 922's structure.[6] A stellar plume is seen extending from the galaxy in the direction of S2,[6] located about 8′ away.[8] However, the stellar plume is not connected to S2, and S2 also has it own tidal structure, which would not be possible if it had already "punched" through NGC 922.[9]
The main galaxy has a stellar mass estimated 5.47 billion times the mass of the Sun (solar mass), while the dwarf companion has 28.2 million solar masses. The net mass of NGC 922 is estimated as 75 billion solar masses within a radius of 13.4 kpc, with 72% being in the form of dark matter and 20% as neutral hydrogen.[6] It is a starburst galaxy,[10] and the collision has resulted in star formation at the rate of 7–8 M☉·yr−1. New star clusters have been formed in the ring or bar with a mean age of 16 million years, whereas older clusters of 50 million years or more are predominantly found in the nuclear region. The tidal plume pointing toward the companion mainly consists of much older stars, indicating not much new star formation has taken place in that feature.[8]
Three supernovae have been observed in NGC 922: SN 2008ho (type IIP, mag. 16.5),[11] SN 2002gw (type II, mag. 17.3),[12] and SN 2024fa (type II, mag. 17.98).[13]
- ^ a b Cite error: The named reference
Skrutskie2006was invoked but never defined (see the help page). - ^ a b c Cite error: The named reference
vaucouleurs1991was invoked but never defined (see the help page). - ^ Cite error: The named reference
Jones2009was invoked but never defined (see the help page). - ^ a b Cite error: The named reference
mould2000was invoked but never defined (see the help page). - ^ a b Cite error: The named reference
SIMBADwas invoked but never defined (see the help page). - ^ a b c d Cite error: The named reference
Wong2006was invoked but never defined (see the help page). - ^ a b Cite error: The named reference
Aranda2011was invoked but never defined (see the help page). - ^ a b c Cite error: The named reference
Pellerin2010was invoked but never defined (see the help page). - ^ a b Cite error: The named reference
Martinez-Delgadowas invoked but never defined (see the help page). - ^ a b Cite error: The named reference
Prestwich2012was invoked but never defined (see the help page). - ^ Transient Name Server entry for SN 2008ho. Retrieved 2 April 2023.
- ^ Transient Name Server entry for SN 2002gw. Retrieved 2 April 2023.
- ^ Transient Name Server entry for SN 2024fa. Retrieved 6 January 2024.