List of Andromeda's satellite galaxies

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Great Andromeda Nebula with M110 at upper left and M32 to the right of the core

The Andromeda Galaxy (M31) has satellite galaxies just like the Milky Way. Orbiting M31 are at least 14 dwarf galaxies: the brightest and largest is M32, which can be seen with a backyard telescope. The second brightest and closest one to M32 is M110. The other galaxies are fainter, and were mostly discovered only starting from the 1970s.

On January 11, 2006, it was announced that Andromeda's faint companion galaxies lie on or close to a single plane running through Andromeda'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.

Table of known satellites[edit]

Andromeda Galaxy's satellites are listed here by discovery (orbital distance is not known).

Andromeda Galaxy's satellites
Name Type Distance from Sun
(million ly)
Magnitude Year
M32 dE2 2.48 +9.2 1749
M110 dE6 2.69 +9.4 1773
NGC 185 dE5 2.01 +11 1787
NGC 147 dE5 2.2 +12 1829
Andromeda I dSph 2.43 +13.2 1970
Andromeda II dSph 2.13 +13 1970
Andromeda III dSph 2.44 +10.3 1970
Andromeda IV * dIm?     1972
Andromeda V dSph 2.52 +15.4 1998
Pegasus Dwarf Spheroidal
(Andromeda VI)
dSph 2.55 +14.5 1998
Cassiopeia Dwarf
(Andromeda VII)
dSph 2.49   1998
Andromeda VIII dSph 2.7 +9.1 2003
Andromeda IX dSph 2.5 +16.2 2004
Andromeda X dSph 2.9 +16.2 2005
Andromeda XI[1] 2006
Andromeda XII[1] 2006
Andromeda XIII[1] 2006
Andromeda XIV[2] 2007
Andromeda XV[2] 2007
Andromeda XVI[2] 2007
Andromeda XVII[2] 2008
Andromeda XVIII[2] 2008
Andromeda XIX[2] 2008
Andromeda XX[2] 2008
Andromeda XXI[2] 2009
Andromeda XXII[2] 2009
Andromeda XXIII[2] 2011
Andromeda XXIV[2] 2011
Andromeda XXV[2] 2011
Andromeda XXVI[2] 2011
Andromeda XXVII[2] 2011
Andromeda XXVIII[3] 2011
Andromeda XXIX[3] 2011
Tidal Stream Northwest
(Tidal Stream E and F)[4]
Tidal Stream Southwest[4] 2009
Triangulum Galaxy*
SA(s)cd 2.59 +6.27 1654?

* It is uncertain whether is a companion galaxy of the Andromeda Galaxy.

Interacting with Andromeda[edit]

Andromeda Galaxy (M31) in Infrared, with the hole arc at bottom right.

New images from NASA's Spitzer Space Telescope shed light on the Andromeda Galaxy's violent past. The images show that one of Andromeda's satellite galaxies, M32, blasted through one of Andromeda's spiral arms a few million years ago. Infrared pictures of Andromeda's two spiral arms demonstrate that they and the prominent star-forming ring are separate structures. The images also show a hole where the rings seem to split into arcs. This hole is where astronomers believe M32 punched through Andromeda's galactic disk.

See also[edit]


External links[edit]