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The Andromeda Galaxy (M31) has satellite galaxies just like the Milky Way. Orbiting M31 are at least 13 dwarf galaxies: the brightest and largest is M110, which can be seen with a basic telescope. The second-brightest and closest one to M31 is M32. The other galaxies are fainter, and were mostly discovered starting from the 1970s.
On January 11, 2006, it was announced that Andromeda Galaxy's faint companion galaxies lie on or close to a single plane running through the Andromeda Galaxy's center. This unexpected distribution is not obviously understood in the context of current models for galaxy formation. The plane of satellite galaxies points toward a nearby group of galaxies (M81 Group), possibly tracing the large-scale distribution of dark matter.
It is unknown whether the Triangulum Galaxy is a satellite of Andromeda.
Table of known satellites
Andromeda Galaxy's satellites are listed here by discovery (orbital distance is not known). Andromeda IV is not included in the list, as it was discovered to be roughly 10 times further than Andromeda from the Milky Way in 2014, and therefore a completely unrelated galaxy.
| Name | Type | Distance from Sun (million ly) |
Right Ascension** | Declination** | Absolute Magnitude[1] | Apparent magnitude | Mass-to-light ratio | 3D distance to M31 (kly) | Year discovered |
Notes |
|---|---|---|---|---|---|---|---|---|---|---|
| M32 | dE2 | 2.48 | 00h 42m 41.877s | +40° 51′ 54.71″ | +8.1 | 1749 | ||||
| M110 | dE6 | 2.69 | 00h 40m 22.054s | +41° 41′ 08.04″ | −16.5 | +8.5 | 1773 | |||
| NGC 185 | dE5 | 2.01 | 00h 38m 57.523s | +48° 20′ 14.86″ | +10.1 | 1787 | ||||
| NGC 147 | dE5 | 2.2 | 00h 33m 12.131s | +48° 30′ 32.82″ | +10.5 | 1829 | ||||
| Andromeda I | dSph | 2.43 | 00h 45m 39.264s | +38° 02′ 35.17″ | −11.8 | +13.6 | 31 ± 6[1] | 1970 | ||
| Andromeda II*** | dSph | 2.13 | 01h 16m 28.136s | +33° 25′ 50.36″ | −12.6 | +13.5 | 13 ± 3[1] | 1970 | ||
| Andromeda III | dSph | 2.44 | 00h 35m 31.777s | +36° 30′ 04.19″ | −10.2 | +15.0 | 19 ± 12[1] | 1970 | ||
| Andromeda V | dSph | 2.52 | 01h 10m 16.952s | +47° 37′ 40.12″ | −9.6 | +15.9 | 78 ± 50[2] | 1998 | ||
| Pegasus Dwarf Spheroidal (Andromeda VI) |
dSph | 2.55 | 23h 51m 46.516s | +24° 34′ 55.69″ | −11.5 | +14.2 | 12 ± 5[2] | 1998 | ||
| Cassiopeia Dwarf (Andromeda VII) |
dSph | 2.49 | 23h 26m 33.321s | +50° 40′ 49.98″ | −13.3 | +12.9 | 7.1 ± 2.8[1] | 1998 | ||
| Andromeda VIII | dSph | 2.7 | 00h 42m 06s | +40° 37′ 00″ | +9.1 | 2003 | Tidally disrupting; identification unclear | |||
| Andromeda IX | dSph | 2.5 | 00h 52m 52.493s | +43° 11′ 55.66″ | −8.3 | +16.2 | 127.2 | 2004 | ||
| Andromeda X | dSph | 2.9 | 01h 06m 34.740s | +44° 48′ 23.31″ | −8.1 | +16.1 | 63 ± 40[1] | 332.7 | 2005 | |
| Andromeda XI[3] | dSph | 00h 46m 20s | +33° 48′ 05″ | −7.3 | 2006 | |||||
| Andromeda XII[3] | dSph | 00h 47m 27s | +33° 22′ 29″ | −6.4 | 2006 | |||||
| Andromeda XIII[3] (Pisces III) | dSph | 00h 51m 49.555s | +33° 00′ 31.40″ | −6.9 | 2006 | |||||
| Andromeda XIV[4] (Pisces IV) | dSph | 00h 41m 35.219s | +29° 41′ 45.87″ | −8.3 | 102 ± 71[1] | 2007 | ||||
| Andromeda XV[4] | dSph | 01h 14m 18.7s | +38° 07′ 02.9″ | −9.4 | 2007 | |||||
| Andromeda XVI[4] (Pisces V) | dSph | 2.143[5] | 00h 59m 29.843s | +32° 22′ 27.96″ | −9.2 | 580.6 | 2007 | |||
| Andromeda XVII[4] | dSph | 00h 37m 07s | +44° 19′ 20″ | −8.5 | 313.1 | 2008 | ||||
| Andromeda XVIII[4] | dSph/Sm | 00h 02m 15.184s | +45° 05′ 19.78″ | 515.3 | 2008 | |||||
| Andromeda XIX[4] | dSph | 00h 19m 32.1s | +35° 02′ 37.1″ | −9.3 | 2008 | |||||
| Andromeda XX[4] | dSph | 00h 07m 30.530s | +35° 07′ 45.94″ | −6.3 | 512.1 | 2008 | ||||
| Andromeda XXI[4] | dSph | 23h 54m 47.7s | +42° 28′ 15″ | −9.9 | 472.9 | 2009 | ||||
| Andromeda XXII[4] | dSph | 00h 27m 40s | +28° 05′ 25″ | −7.0 | 910 | 2009 | ||||
| Andromeda XXIII[4] | dIrr | 01h 29m 21.944s | +38° 43′ 05.97″ | 427.3 | 2011 | |||||
| Andromeda XXIV[4] | 01h 18m 30s | +46° 21′ 58″ | 401.2 | 2011 | ||||||
| Andromeda XXV[4] | 00h 30m 08.9s | +46° 51′ 07″ | 319.6 | 2011 | ||||||
| Andromeda XXVI[4] | 00h 23m 45.6s | +47° 54′ 58″ | 489.2 | 2011 | ||||||
| Andromeda XXVII[4] | 00h 37m 27.1s | +45° 23′ 13″ | 2011 | Tidally disrupted[6] | ||||||
| Andromeda XXVIII[7] | dSph | 22h 32m 41.449s | +31° 12′ 59.10″ | 2011 | ||||||
| Andromeda XXIX[7] | dIrr | 23h 58m 55.440s | +30° 45′ 22.09″ | 636 | 2011 | |||||
| Andromeda XXX (Cassiopeia II)[8] | dSph? | 00h 36m 34.9s | +49° 38′ 48″ | |||||||
| Andromeda XXXI (Lacerta I)[8] | dSph? | 22h 58m 16.3s | +41° 17′ 28″ | 2013 | ||||||
| Andromeda XXXII (Cassiopeia III)[8] | dSph? | 00h 35m 59.4s | +51° 33′ 35″ | 2013 | ||||||
| Andromeda XXXIII (Perseus I)[8] | dSph? | 03h 01m 23.6s | +40° 59′ 18″ | Zdroj:https://en.wikipedia.org?pojem=List_of_Andromeda's_satellite_galaxies |