NGC 24 is a spiral galaxy in the southern constellation of Sculptor, about 23.8 million light years distant from the Milky Way. It was discovered by British astronomer William Herschel in 1785, and measures some 40,000 light-years across. The general shape of this galaxy is specified by its morphological classification of SA(s)c, which indicates it is an unbarred spiral with no ring-like structure and moderate to loosely-wound spiral arms.
This galaxy is positioned in the vicinity of the Sculptor Group, but is actually a background object that is more than three times as distant. It may form a pair with another background galaxy, NGC 45. This galaxy belongs to the following galactic groups: [CHM2007] LDC 26, [CHM2007] HDC 7, [TSK2008] 355 and [TKT2016] 15. this galaxy has neighboring galaxies nearby: NGC 45, NGC 55, NGC 59, NGC 247, NGC 253, NGC 300, NGC 625, NGC 7793, IC 1574.
Historical Identification[]
Per Dreyer, NGC 24 (= GC 10 = JH 2308 = WH III 461, 1860 RA 00 02 47, NPD 115 45.0) is "very faint, considerably large, much extended, gradually brighter middle". The position precesses to RA 00 09 54.8, Dec -24 58 14, only 0.5 arcmin southwest of the center of the galaxy listed above and well within its outline, so the identification is certain.
Physical Information[]
Based on a recessional velocity of 555 km/sec (and H0 = 70 km/sec/Mpc), NGC 24 is about 25 to 30 million light-years away, but for such distances peculiar (non-Hubble-redshift) velocities can significantly affect the accuracy of the distance estimate. Unfortunately, redshift-independent estimates range from as little as 3 million to as much as 35 million light-years, inspiring far less confidence. However, the galaxy's apparent size of about 6.9 by 1.5 arcmin (from the images below) makes most sense if its distance is in the 25 million light-year range, in which case it would be about 50 to 55 thousand light-years across. It has been suggested that NGC 24 and 45 are a pair, as they have similar recessional velocities and if at similar distances their two degree separation corresponds to less than a million light-years. The latter galaxy is more certainly about 25 million light-years away, so if they really are a pair it would confirm the estimate made in this entry; but both galaxies' distances are sufficiently uncertain that the suggestion that they are a pair cannot inspire much confidence. Update: The discussion of the 2.7 arcmin wide HST image below (released on Sep 26, 2016) states that the distance of the galaxy is about 25 million light-years, it is about 40 thousand light-years across, and about 80% of the mass of its halo is so-called "dark matter"; so the distance and size estimates in this entry appear to be more or less in agreement with most current thinking.
Coordinates[]
The coordinates of this galaxy:
- Galactic longitude: 043.691566
- Galactic latitude: -80.434792
position in the sky[]
This photo shows where the NGC 24 is located:
NGC 24 location:
Maps and Photos[]
photo of NGC 24 from Sky Map.org:
Below, a 12 arcmin wide DSS image centered on NGC 24:
Below, a 6 arcmin wide image of the galaxy:
Below, a 2.7 arcmin wide HST image of the inner half of the galaxy:
Below, a 1.6 arcmin wide image of the central part of the galaxy:
Below, a 12 arcmin wide DSS image centered on NGC 24, also showing PGC 783199, 783608 and 785296:
Below, a 2 degree wide DSS image centered between possible companions NGC 24 and 45(The image is centered at RA 00 00 12.0, Dec -24 06 00):
Fluxes[]
| ? | ? | ? | ? | ? |
|---|---|---|---|---|
| U | 12.12 | [0.13] | D | 2007ApJS..173..185G |
| B (AB) | 12.20 | [0.03] | C | 2014MNRAS.445..881C |
| V (AB) | 11.58 | [0.03] | C | 2014MNRAS.445..881C |
| R (AB) | 11.46 | [0.03] | C | 2014MNRAS.445..881C |
| I | 11.5 | [~] | D | 2005MNRAS.361...34D |
| J | 9.711 | [0.022] | C | 2006AJ....131.1163S |
| H | 9.108 | [0.028] | C | 2006AJ....131.1163S |
| K | 8.955 | [0.040] | C | 2006AJ....131.1163S |
Identifiers[]
| ? | ? | ? | ? |
|---|---|---|---|
| NGC 24 | ESO-LV 472-0160 | 2MASX J00095654-2457472 | SGC 000724-2514.4 |
| AGC 20114 | HIPASS J0009-24 | MCG-04-01-018 | UGCA 2 |
| AM 0007-251 | IRAS 00073-2514 | 2MFGC 135 | [CHM2007] LDC 26 J000956.54-2457472 |
| 6dFGS gJ000956.2-245752 | IRAS F00074-2514 | PSCz Q00073-2514 | [CHM2007] HDC 7 J000956.54-2457472 |
| ESO 472-16 | LEDA 701 | RR95 4a | [M98c] 000724.0-251424 |