| Sextans B | |
|---|---|
 Sextans B, imaged by the 4-meter Telescope atKitt Peak National Observatory | |
| Observation data (J2000epoch) | |
| Constellation | Sextans |
| Right ascension | 10h 00m 00.1s[1] |
| Declination | +05° 19′ 56″[1] |
| Redshift | 301 ± 1 km/s[1] |
| Distance | 4.44 ± 0.23Mly (1.36 ± 0.07Mpc)[2][3] |
| Apparent magnitude (V) | 11.9[1] |
| Characteristics | |
| Type | ImIV–V[1] |
| Size | ~8,900 ly (2.73 kpc) (estimated)[1] |
| Apparent size (V) | 5.1′ × 3.5′[1] |
| Other designations | |
| DDO 70,UGC 5373,MCG +01-26-005,PGC 28913,CGCG 036-012 | |
Sextans B (also known asUGC 5373 andDDO 70) is anirregulargalaxy that may be part of theLocal Group, or lie just beyond it. The earliest known reference to this galaxy is from a 1954 paper byEdison Pettit inThe Astrophysical Journal, where it was listed as "Wilson Dwarf".[4]
Sextans B is 4.44 millionlight-years away fromEarth and thus is one of the most distant members of the Local Group, if it is indeed a member. It forms a pair with its neighbouring galaxySextans A.[5] It is a type Ir IV–V galaxy according to thegalaxy morphological classification scheme.[6] Sextans B may also be gravitationally associated with the galaxiesNGC 3109 and theAntlia Dwarf.[7]
Sextans B has a uniform stellar population,[8] but the interstellar medium in it may be inhomogeneous.[9] Its mass is estimated to be about 2×108 times the mass of theSun, of which 5.5×107 is in the form of atomichydrogen.[8] Star formation in the galaxy seems to have proceeded in distinct periods of low intensity, separated by shorter periods of no activity.[8] The existence ofCepheid variables in the galaxy implies that Sextans B contains at least some young stars.[6] Themetallicity of Sextans B is very low, with a value of approximately Z = 0.001.[8] Sextans B is receding from theMilky Way with a speed of approximately 300 kilometres per second (190 mi/s),[9] and probably lies just outside the edge of theLocal Group, so as its neighbourSextans A.[10]
Fiveplanetary nebulae have been identified in Sextans B, which is one of the smallest galaxies where planetary nebulae have been observed. These appear point-like and can be identified by their spectral emission lines.[11] It also contains a massiveglobular cluster.[12]
Although nosupernovae have been observed in Sextans B, the galaxy is close enough for classicalnovae to be detected. The first confirmed nova in this galaxy was discovered byATLAS at magnitude 18.553 on 10 November 2024, and designated AT 2024aawe.[13]
