List of Andromeda's satellite galaxies

The Andromeda Galaxy (M31) is one of the closest big galaxies to us, and like our own Milky Way, it has smaller galaxies that orbit around it. These are called satellite galaxies. Scientists have found at least 35 of these smaller galaxies around Andromeda. The brightest and easiest to see with a basic telescope is M110. Another bright one is M32, which is the second-brightest and closest to Andromeda.

The Andromeda Galaxy with M110 at the bottom and M32 to the upper left of the core.

Most of these smaller galaxies are quite faint and were discovered mainly starting in the 1970s. In 2006, scientists found something surprising: many of Andromeda's faint companion galaxies line up along a single plane that goes through the center of Andromeda. This is puzzling because current ideas about how galaxies form don't easily explain this arrangement. This line of galaxies points toward a group of galaxies called the M81 Group, and it might be related to the hidden stuff called dark matter that we can't see but that holds galaxies together.

We also don't know for sure if the Triangulum Galaxy is one of Andromeda's satellites or if it orbits on its own. Studying these satellite galaxies helps scientists learn more about how big galaxies like Andromeda grow and change over time.

Table of known satellites

The Andromeda Galaxy has many smaller galaxies orbiting around it. These are called satellite galaxies. They are listed here in the order they were discovered, but we don’t know exactly how far they are from Andromeda.

**Andromeda Galaxy's satellites**
Name	Type	Distance from Sun (million ly)	Right Ascension	Declination	Absolute Magnitude	Apparent magnitude	Mass-to-light ratio	3D distance to M31 (kly)	Year discovered
M32	dE2	2.48	00^h 42^m 41.877^s	+40° 51′ 54.71″		+8.1			1749
M110	dE6	2.69	00^h 40^m 22.054^s	+41° 41′ 08.04″	−16.5	+8.5			1773
NGC 185	dE5	2.01	00^h 38^m 57.523^s	+48° 20′ 14.86″		+10.1			1787
NGC 147	dE5	2.2	00^h 33^m 12.131^s	+48° 30′ 32.82″		+10.5			1829
Andromeda I	dSph	2.43	00^h 45^m 39.264^s	+38° 02′ 35.17″	−11.8	+13.6	31 ± 6		1970
Andromeda II	dSph	2.13	01^h 16^m 28.136^s	+33° 25′ 50.36″	−12.6	+13.5	13 ± 3		1970
Andromeda III	dSph	2.44	00^h 35^m 31.777^s	+36° 30′ 04.19″	−10.2	+15.0	19 ± 12		1970
Andromeda V	dSph	2.52	01^h 10^m 16.952^s	+47° 37′ 40.12″	−9.6	+15.9	78 ± 50		1998
Pegasus Dwarf Spheroidal (Andromeda VI)	dSph	2.55	23^h 51^m 46.516^s	+24° 34′ 55.69″	−11.5	+14.2	12 ± 5		1998
Cassiopeia Dwarf (Andromeda VII)	dSph	2.49	23^h 26^m 33.321^s	+50° 40′ 49.98″	−13.3	+12.9	7.1 ± 2.8		1998
Andromeda VIII	dSph	2.7	00^h 42^m 06^s	+40° 37′ 00″		+9.1			2003
Andromeda IX	dSph	2.5	00^h 52^m 52.493^s	+43° 11′ 55.66″	−8.3	+16.2		127.2	2004
Andromeda X	dSph	2.9	01^h 06^m 34.740^s	+44° 48′ 23.31″	−8.1	+16.1	63 ± 40	332.7	2005
Andromeda XI	dSph		00^h 46^m 20^s	+33° 48′ 05″	−7.3				2006
Andromeda XII	dSph		00^h 47^m 27^s	+33° 22′ 29″	−6.4				2006
Andromeda XIII (Pisces III)	dSph		00^h 51^m 49.555^s	+33° 00′ 31.40″	−6.9				2006
Andromeda XIV (Pisces IV)	dSph		00^h 41^m 35.219^s	+29° 41′ 45.87″	−8.3		102 ± 71		2007
Andromeda XV	dSph		01^h 14^m 18.7^s	+38° 07′ 02.9″	−9.4				2007
Andromeda XVI (Pisces V)	dSph	2.143	00^h 59^m 29.843^s	+32° 22′ 27.96″	−9.2			580.6	2007
Andromeda XVII	dSph		00^h 37^m 07^s	+44° 19′ 20″	−8.5			313.1	2008
Andromeda XVIII	dSph/Sm		00^h 02^m 15.184^s	+45° 05′ 19.78″				515.3	2008
Andromeda XIX	dSph		00^h 19^m 32.1^s	+35° 02′ 37.1″	−9.3				2008
Andromeda XX	dSph		00^h 07^m 30.530^s	+35° 07′ 45.94″	−6.3			512.1	2008
Andromeda XXI	dSph		23^h 54^m 47.7^s	+42° 28′ 15″	−9.9			472.9	2009
Andromeda XXII	dSph		00^h 27^m 40^s	+28° 05′ 25″	−7.0			910	2009
Andromeda XXIII	dIrr		01^h 29^m 21.944^s	+38° 43′ 05.97″				427.3	2011
Andromeda XXIV			01^h 18^m 30^s	+46° 21′ 58″				401.2	2011
Andromeda XXV			00^h 30^m 08.9^s	+46° 51′ 07″				319.6	2011
Andromeda XXVI			00^h 23^m 45.6^s	+47° 54′ 58″				489.2	2011
Andromeda XXVII			00^h 37^m 27.1^s	+45° 23′ 13″					2011
Andromeda XXVIII	dSph		22^h 32^m 41.449^s	+31° 12′ 59.10″	−8.8				2011
Andromeda XXIX	dIrr		23^h 58^m 55.440^s	+30° 45′ 22.09″				636	2011
Andromeda XXX (Cassiopeia II)	dSph?		00^h 36^m 34.9^s	+49° 38′ 48″
Andromeda XXXI (Lacerta I)	dSph?		22^h 58^m 16.3^s	+41° 17′ 28″					2013
Andromeda XXXII (Cassiopeia III)	dSph?	2.74	00^h 35^m 59.4^s	+51° 33′ 35″				508	2013
Andromeda XXXIII (Perseus I)	dSph?	2.41	03^h 01^m 23.6^s	+40° 59′ 18″				1,140	2013
Andromeda XXXVI	dSph		01 16 39.91	+47 39 13.3			64 ±30	388,000	2026
Tidal Stream Northwest (Tidal Stream E and F)			00^h 20^m 00^s	+46° 00′ 00″					2009
Tidal Stream Southwest			00^h 30^m 00^s	+37° 30′ 00″					2009
Pegasus V galaxy (Peg V, Andromeda XXXIV)	d	682 kpc (2.22 Mly)	23^h 18^m 27.8^s±0.1	+33° 21′ 32″±3	−6.3			800	2022
Andromeda XXXV		3.02	00^h 26^m 38.6^s	+40° 06′ 29.3″	-5.2			520	2025
Triangulum Galaxy (M33)	SA(s)cd	2.59	01^h 33^m 50.883^s	+30° 39′ 36.54″		+6.27		750	1654?

List of Andromeda's satellite galaxies

Table of known satellites

Images

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