List of Andromeda's satellite galaxies

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The Andromeda Galaxy with M110 at upper left and M32 to the right of the core Pic iroberts1.jpg
The Andromeda Galaxy 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 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.

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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.

Andromeda Galaxy's satellites
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 dE22.4800h 42m 41.877s+40° 51′ 54.71″+8.11749
M110 dE62.6900h 40m 22.054s+41° 41′ 08.04″−16.5+8.51773
NGC 185 dE52.0100h 38m 57.523s+48° 20′ 14.86″+10.11787
NGC 147 dE52.200h 33m 12.131s+48° 30′ 32.82″+10.51829
Andromeda I dSph 2.4300h 45m 39.264s+38° 02′ 35.17″−11.8+13.631 ± 6 [1] 1970
Andromeda II***dSph2.1301h 16m 28.136s+33° 25′ 50.36″−12.6+13.513 ± 3 [1] 1970
Andromeda III dSph2.4400h 35m 31.777s+36° 30′ 04.19″−10.2+15.019 ± 12 [1] 1970
Andromeda V dSph2.5201h 10m 16.952s+47° 37′ 40.12″−9.6+15.978 ± 50 [2] 1998
Pegasus Dwarf Spheroidal
(Andromeda VI)		dSph2.5523h 51m 46.516s+24° 34′ 55.69″−11.5+14.212 ± 5 [2] 1998
Cassiopeia Dwarf
(Andromeda VII)		dSph2.4923h 26m 33.321s+50° 40′ 49.98″−13.3+12.97.1 ± 2.8 [1] 1998
Andromeda VIII dSph2.700h 42m 06s+40° 37′ 00″+9.12003Tidally disrupting; identification unclear
Andromeda IX dSph2.500h 52m 52.493s+43° 11′ 55.66″−8.3+16.2127.22004
Andromeda X dSph2.901h 06m 34.740s+44° 48′ 23.31″−8.1+16.163 ± 40 [1] 332.72005
Andromeda XI [3] dSph00h 46m 20s+33° 48′ 05″−7.32006
Andromeda XII [3] dSph00h 47m 27s+33° 22′ 29″−6.42006
Andromeda XIII [3] (Pisces III)dSph00h 51m 49.555s+33° 00′ 31.40″−6.92006
Andromeda XIV [4] (Pisces IV)dSph00h 41m 35.219s+29° 41′ 45.87″−8.3102 ± 71 [1] 2007
Andromeda XV [4] dSph01h 14m 18.7s+38° 07′ 02.9″−9.42007
Andromeda XVI [4] (Pisces V)dSph2.143 [5] 00h 59m 29.843s+32° 22′ 27.96″−9.2580.62007
Andromeda XVII [4] dSph00h 37m 07s+44° 19′ 20″−8.5313.12008
Andromeda XVIII [4] dSph/Sm00h 02m 15.184s+45° 05′ 19.78″515.32008
Andromeda XIX [4] dSph00h 19m 32.1s+35° 02′ 37.1″−9.32008
Andromeda XX [4] dSph00h 07m 30.530s+35° 07′ 45.94″−6.3512.12008
Andromeda XXI [4] dSph23h 54m 47.7s+42° 28′ 15″−9.9472.92009
Andromeda XXII [4] dSph00h 27m 40s+28° 05′ 25″−7.09102009
Andromeda XXIII [4] dIrr01h 29m 21.944s+38° 43′ 05.97″427.32011
Andromeda XXIV [4] 01h 18m 30s+46° 21′ 58″401.22011
Andromeda XXV [4] 00h 30m 08.9s+46° 51′ 07″319.62011
Andromeda XXVI [4] 00h 23m 45.6s+47° 54′ 58″489.22011
Andromeda XXVII [4] 00h 37m 27.1s+45° 23′ 13″2011Tidally disrupted [6]
Andromeda XXVIII [7] dSph22h 32m 41.449s+31° 12′ 59.10″2011
Andromeda XXIX [7] dIrr23h 58m 55.440s+30° 45′ 22.09″6362011
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″2013
Tidal Stream Northwest
(Tidal Stream E and F) [9] 		00h 20m 00s+46° 00′ 00″2009
Tidal Stream Southwest [9] 00h 30m 00s+37° 30′ 00″2009
Pegasus V galaxy (Peg V)d682 kpc (2.22 Mly)23h 18m 27.8s±0.1+33° 21′ 32″±3−6.3245 kpc (800 kly)2022 [10] [11] [12]
Triangulum Galaxy*
(M33)		SA(s)cd2.5901h 33m 50.883s+30° 39′ 36.54″+6.271654?It is around 750000 light years from Andromeda. [13] Its relation to Andromeda is uncertain.

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

**RA/DEC values marked in Italics are rough estimates.

***Martin et al. (2009) gave aliases to several satellite galaxies of the Andromeda Galaxy that are located in Pisces. [14] However, the name Pisces II was later used for a different galaxy that is a satellite of the Milky Way, [15] so it is not used here.

See also

Related Research Articles

<span class="mw-page-title-main">Local Group</span> Group of galaxies that includes the Milky Way

The Local Group is the galaxy group that includes the Milky Way, where Earth is located. It has a total diameter of roughly 3 megaparsecs (10 million light-years; 9×1019 kilometres), and a total mass of the order of 2×1012 solar masses (4×1042 kg). It consists of two collections of galaxies in a "dumbbell" shape; the Milky Way and its satellites form one lobe, and the Andromeda Galaxy and its satellites constitute the other. The two collections are separated by about 800 kiloparsecs (3×10^6 ly; 2×1019 km) and are moving toward one another with a velocity of 123 km/s. The group itself is a part of the larger Virgo Supercluster, which may be a part of the Laniakea Supercluster. The exact number of galaxies in the Local Group is unknown as some are occluded by the Milky Way; however, at least 80 members are known, most of which are dwarf galaxies.

<span class="mw-page-title-main">Andromeda Galaxy</span> Barred spiral galaxy in the Local Group

The Andromeda Galaxy is a barred spiral galaxy and is the nearest major galaxy to the Milky Way. It was originally named the Andromeda Nebula and is cataloged as Messier 31, M31, and NGC 224. Andromeda has a D25 isophotal diameter of about 46.56 kiloparsecs (152,000 light-years) and is approximately 765 kpc (2.5 million light-years) from Earth. The galaxy's name stems from the area of Earth's sky in which it appears, the constellation of Andromeda, which itself is named after the princess who was the wife of Perseus in Greek mythology.

<span class="mw-page-title-main">Triangulum Galaxy</span> Spiral galaxy in the constellation Triangulum

The Triangulum Galaxy is a spiral galaxy 2.73 million light-years (ly) from Earth in the constellation Triangulum. It is catalogued as Messier 33 or NGC (New General Catalogue) 598. With the D25 isophotal diameter of 18.74 kiloparsecs (61,100 light-years), the Triangulum Galaxy is the third-largest member of the Local Group of galaxies, behind the Andromeda Galaxy and the Milky Way.

<span class="mw-page-title-main">Dwarf spheroidal galaxy</span> Small, low-luminosity galaxy with an old stellar population and little dust

A dwarf spheroidal galaxy (dSph) is a term in astronomy applied to small, low-luminosity galaxies with very little dust and an older stellar population. They are found in the Local Group as companions to the Milky Way and as systems that are companions to the Andromeda Galaxy (M31). While similar to dwarf elliptical galaxies in appearance and properties such as little to no gas or dust or recent star formation, they are approximately spheroidal in shape and generally have lower luminosity.

<span class="mw-page-title-main">Andromeda I</span> Dwarf galaxy in the constellation Andromeda

Andromeda I is a dwarf spheroidal galaxy (dSph) about 2.40 million light-years away in the constellation Andromeda. Andromeda I is part of the local group of galaxies and a satellite galaxy of the Andromeda Galaxy (M31). It is roughly 3.5 degrees south and slightly east of M31. As of 2005, it is the closest known dSph companion to M31 at an estimated projected distance of ~40 kpc or ~150,000 light-years.

<span class="mw-page-title-main">Pisces Dwarf</span>

The Pisces Dwarf, also known as Pisces I, is an irregular dwarf galaxy that is part of the Local Group. The galaxy, taking its name from the constellation Pisces where it appears, is suspected of being a satellite galaxy of the Triangulum Galaxy (M33). It displays a blueshift, as it is approaching the Milky Way at 287 km/s. It may be transition-type galaxy, somewhere between dwarf spheroidal and dwarf irregular. Alternatively, it may be a rare, but statistically acceptable, version of one of the two types.

The Milky Way has several smaller galaxies gravitationally bound to it, as part of the Milky Way subgroup, which is part of the local galaxy cluster, the Local Group.

Andromeda IX is a dwarf spheroidal satellite of the Andromeda Galaxy. It was discovered in 2004 by resolved stellar photometry from the Sloan Digital Sky Survey (SDSS), by Zucker et al. (2004). At the time of its discovery, it was the galaxy with the lowest known surface brightness, ΣV ≃ 26.8mags arcsec−2 and the faintest galaxy known from its intrinsic absolute brightness.

<span class="mw-page-title-main">Andromeda II</span> Dwarf spheroidal galaxy in the constellation Andromeda

Andromeda II is a dwarf spheroidal galaxy about 2.22 Mly away in the constellation Pisces. While part of the Local Group, it is not quite clear if it is a satellite of the Andromeda Galaxy or the Triangulum Galaxy.

Andromeda III is a dwarf spheroidal galaxy about 2.44 million light-years away in the constellation Andromeda. It is part of the Local Group and is a satellite galaxy of the Andromeda Galaxy (M31). The galaxy was discovered by Sidney van den Bergh on photographic plates taken in 1970 and 1971.

Andromeda V is a dwarf spheroidal galaxy about 2.52 Mly away in the constellation Andromeda.

Segue 1 is a dwarf spheroidal galaxy or globular cluster situated in the Leo constellation and discovered in 2006 by Sloan Digital Sky Survey. It is located at a distance of about 23 kpc from the Sun and moves away from the Sun with the velocity of about 206 km/s. Segue 1 has a noticeably elongated shape with the half-light radius of about 30 pc. This elongation may be caused by the tidal forces acting from the Milky Way galaxy if Segue 1 is being tidally disrupted now.

Pisces II is a dwarf spheroidal galaxy situated in the Pisces constellation and discovered in 2010 in the data obtained by the Sloan Digital Sky Survey. The galaxy is located at the distance of about 180 kpc (kiloparsecs) from the Sun. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an elongated shape with the half-light radius of about 60 pc and ratio of the axis of about 5:3.

Andromeda XXI is a moderately bright dwarf spheroidal galaxy about 859 ± 51 kiloparsecs (2.80 ± 0.17 Mly) away from the Sun in the constellation Andromeda. It is the fourth largest Local Group dwarf spheroidal galaxy. The discovery arose from the first year data of a photometric survey of the M31/M33 subgroupings of the Local Group by the Pan-Andromeda Archaeological Survey (PAndAS). This survey was conducted with the Megaprime/MegaCam wide-field camera mounted on the Canada-France-Hawaii Telescope.

Andromeda XXII is a low surface brightness dwarf spheroidal galaxy about 940–1,033 kiloparsecs away from the Sun in the constellation Pisces, of the Local Group.

Andromeda XIX is a satellite galaxy of the Andromeda Galaxy (M31), a member of the Local Group, like the Milky Way Galaxy. Andromeda XIX is considered "the most extended dwarf galaxy known in the Local Group", and has been shown to have a half-light radius of 1.7 kiloparsec (kpc). It was discovered by the Canada–France–Hawaii Telescope, and is thought to be a dwarf galaxy.

<span class="mw-page-title-main">Andromeda XVIII</span> Galaxy in constellation Andromeda

Andromeda XVIII, discovered in 2008, is a dwarf spheroidal galaxy, which is a satellite of the Andromeda Galaxy (M31). It is one of the 14 known dwarf galaxies orbiting M31. It was announced in 2010 that the orbiting galaxies lie close to a plane running through M31's center.

References

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  4. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Discovery of the Local Group Galaxies
  5. ↑ Monelli, Matteo; Martínez-Vázquez, Clara E.; Bernard, Edouard J.; Gallart, Carme; Skillman, Evan D.; Weisz, Daniel R.; Dolphin, Andrew E.; Hidalgo, Sebastian L.; Cole, Andrew A.; Martin, Nicolas F.; Aparicio, Antonio; Cassisi, Santi; Boylan-Kolchin, Michael; Mayer, Lucio; McConnachie, Alan; McQuinn, Kristen B. W.; Navarro, Julio F. (2016). "The Islands Project. I. Andromeda Xvi, an Extremely Low Mass Galaxy Not Quenched by Reionization". The Astrophysical Journal. 819 (2): 147. arXiv: 1603.00625 . Bibcode:2016ApJ...819..147M. doi: 10.3847/0004-637X/819/2/147 . S2CID   32263075.
  6. ↑ Preston, Janet; Collins, Michelle L. M.; Ibata, Rodrigo A.; Tollerud, Erik J.; Rich, R. Michael; Bonaca, Ana; McConnachie, Alan W.; Mackey, Dougal; Lewis, Geraint F.; Martin, Nicolas F.; Peñarrubia, Jorge; Chapman, Scott C.; Delorme, Maxime (2019). "A dwarf disrupting - Andromeda XXVII and the North West Stream". Monthly Notices of the Royal Astronomical Society. 490 (2): 2905–2917. arXiv: 1909.09661 . Bibcode:2019MNRAS.490.2905P. doi:10.1093/mnras/stz2529.
  7. 1 2 Moore, Nicole Casal (7 Nov 2011), "Newly found dwarf galaxies could help reveal the nature of dark matter", News Service, University of Michigan, retrieved 10 Dec 2011 (reprinted in R&D Magazine)
  8. 1 2 3 4 McConnachie, Alan W. (2012). "The observed properties of dwarf galaxies in and around the Local Group". The Astronomical Journal. 144 (1): 4. arXiv: 1204.1562 . Bibcode:2012AJ....144....4M. doi:10.1088/0004-6256/144/1/4. S2CID   118515618.
  9. 1 2 New tidal streams found in Andromeda reveal history of galactic mergers
  10. ↑ "Pegasus V: New Ultra-Faint Dwarf Galaxy Spotted in Outskirts of Andromeda". Sci-News. 1 July 2022.
  11. ↑ University of Surrey (30 June 2022). "New fossil galaxy discovery could answer important questions about the history of the universe". EurkAlert!. AAAS.
  12. ↑ Collins, Michelle L. M.; Charles, Emily J. E.; Martínez-Delgado, David; Monelli, Matteo; Karim, Noushin; Donatiello, Giuseppe; Tollerud, Erik J.; Boschin, Walter (2022). "Pegasus V/Andromeda XXXIV–a newly discovered ultrafaint dwarf galaxy on the outskirts of Andromeda". Monthly Notices of the Royal Astronomical Society: Letters. 515 (1): L72–L77. arXiv: 2204.09068 . Bibcode:2022MNRAS.515L..72C. doi:10.1093/mnrasl/slac063.
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  15. ↑ Belokurov, V.; Walker, M. G.; Evans, N. W.; Gilmore, G.; Irwin, M. J.; Just, D.; Koposov, S.; Mateo, M.; Olszewski, E.; Watkins, L.; Wyrzykowski, L. (2010). "Big Fish, Little Fish: Two New Ultra-Faint Satellites of the Milky Way". The Astrophysical Journal. 712 (1): L103–L106. arXiv: 1002.0504 . Bibcode:2010ApJ...712L.103B. doi:10.1088/2041-8205/712/1/L103. S2CID   29195107.
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