Local Group

The Local Group is the galaxy group that includes the Milky Way. Its has a total diameter of roughly 3 Mpc (or 10 Mly1023 m), and a total mass of the order of 2×1012 solar masses (4×1042 kg).[1] It consists of two clusters of galaxies in a "dumbbell" shape, the Milky Way and its satellites on one hand, and the Andromeda Galaxy and its satellites on the other. The two clusters are separated by about 0.8 Mpc and move towards one another with a velocity of 123 km/h.[2] The group itself is a part of the larger Virgo Supercluster, which may be a part of the Laniakea Supercluster. The total number of galaxies in the Local Group is unknown (due to its partial occlusion by the Milky Way) but known to exceed 54, most of them being dwarf galaxies.

The two largest members, the Andromeda Galaxy and the Milky Way, are both spiral galaxies with masses of about 1012 solar masses each, and each have their own system of satellite galaxies:

The Triangulum Galaxy is the third largest member of the Local Group, at about 5×1010 M, and the third spiral galaxy.[5] It may or may not be a companion to the Andromeda Galaxy. Pisces Dwarf Galaxy is equidistant from the Andromeda Galaxy and the Triangulum Galaxy, so it may be a satellite of either.[6]

The membership of NGC 3109, with its companions Sextans A and the Antlia Dwarf Galaxy, is uncertain due to extreme distances from the center of the Local Group.[2] The other members of the group are likely gravitationally secluded from these large subgroups: IC 10, IC 1613, Phoenix Dwarf Galaxy, Leo A, Tucana Dwarf Galaxy, Cetus Dwarf Galaxy, Pegasus Dwarf Irregular Galaxy, Wolf–Lundmark–Melotte, Aquarius Dwarf Galaxy, and Sagittarius Dwarf Irregular Galaxy.[7]

Local Group and nearest galaxies
Local Group of galaxies, including the massive members Messier 31 (Andromeda Galaxy) and Milky Way, as well as other nearby galaxies.
VLT Shows Milky Way's Neighbouring Galaxies Have Different History
Distribution of the iron content (in logarithmic scale) in four dwarf neighbouring galaxies of the Milky Way

History

The term "The Local Group" was introduced by Edwin Hubble in Chapter VI of his 1936 book The Realm of the Nebulae.[8] There, he described it as "a typical small group of nebulae which is isolated in the general field" and delineated, by decreasing luminosity, its members to be M31, Milky Way, M33, Large Magellanic Cloud, Small Magellanic Cloud, M32, NGC 205, NGC 6822, NGC 185, IC 1613 and NGC 147. He also identified IC 10 as a possible part of Local Group.

By 2003, the number of known Local Group members had increased from his initial 12 to 36.[9]

Component galaxies

Map

Sextans BSextans AMilky WayLeo I (dwarf galaxy)Canes DwarfLeo II (dwarf galaxy)NGC 6822Phoenix DwarfTucana DwarfWolf-Lundmark-MelotteCetus DwarfIC 1613SagDIGAquarius DwarfTriangulum GalaxyNGC 185NGC 147IC 10Andromeda GalaxyM110Leo ANGC 3109Antlia DwarfLGS 3Pegasus DwarfAndromeda IIAndromeda IIIAndromeda I
Local Group (clickable map)

List of galactic bodies

Spiral galaxies
name type constellation notes
Andromeda Galaxy (M31, NGC 224) SA(s)b Andromeda Largest galaxy in the group,[10]

at about 125% of the mass of the Milky Way.[2] Diameter: 220 kly, mass: (1.15±0.35)×1012 M, number of stars: ca. 1012.

Milky Way SBbc Sagittarius (centre)

Diameter: 175±25 kly, mass: (1.3±0.3)×1012 M, number of stars: (2.5±1.5)×1011.[11]

Triangulum Galaxy (M33, NGC 598) SA(s)cd Triangulum Third largest, only unbarred spiral galaxy and possible satellite of the Andromeda Galaxy.

Diameter: 60 kly, mass: 5×1010 M, number of stars: 4×1010.

Elliptical galaxies
name type constellation notes
M32 (NGC 221) E2 Andromeda Satellite of the Andromeda Galaxy
Irregular galaxies
name type constellation notes
Wolf–Lundmark–Melotte (WLM, DDO 221) Ir+ Cetus
IC 10 KBm or Ir+ Cassiopeia
Small Magellanic Cloud (SMC, NGC 292) SB(s)m pec Tucana Satellite of Milky Way, 6th largest galaxy in the local group with mass of between 7.5 and 8 billion solar mass.
Canis Major Dwarf Irr Canis Major Satellite of Milky Way
Pisces Dwarf (LGS3) Irr Pisces Possible satellite of the Triangulum Galaxy
IC 1613 (UGC 668) IAB(s)m V Cetus
Phoenix Dwarf Irr Phoenix
Large Magellanic Cloud (LMC) Irr/SB(s)m Dorado Fourth largest member of the group, satellite of Milky Way, mass between 10 and 85 billion solar masses. Recent finding puts it at 10% mass of Milky Way Galaxy.[12]
Leo A (Leo III) IBm V Leo
Sextans B (UGC 5373) Ir+IV-V Sextans
NGC 3109 Ir+IV-V Hydra
Sextans A (UGCA 205) Ir+V Sextans
Aquarius Dwarf (DDO 210) IB(s)m Aquarius Distance 3.2 million light years. Quite isolated in space, membership to Local Group established in 1999.[13]
Dwarf elliptical galaxies
name type constellation notes
M110 (NGC 205) dE6p Andromeda Satellite of the Andromeda Galaxy and 5th largest galaxy with the mass of 9.3 billion solar masses.
NGC 147 (DDO 3) dE5 pec Cassiopeia Satellite of the Andromeda Galaxy
SagDIG (Sagittarius Dwarf Irregular Galaxy) IB(s)m V Sagittarius Most remote from barycenter member thought to be in the Local Group.[13]
NGC 6822 (Barnard's Galaxy) IB(s)m IV-V Sagittarius
Pegasus Dwarf (Pegasus Dwarf Irregular, DDO 216) Irr Pegasus
Dwarf spheroidal galaxies
name type constellation notes
Boötes I dSph Boötes
Cetus Dwarf dSph/E4 Cetus
Canes Venatici I Dwarf and Canes Venatici II Dwarf dSph Canes Venatici
KKs 3 dSph
Andromeda III dE2 Andromeda Satellite of the Andromeda Galaxy
NGC 185 dE3 pec Cassiopeia Satellite of the Andromeda Galaxy
Andromeda I dE3 pec Andromeda Satellite of the Andromeda Galaxy
Sculptor Dwarf (E351-G30) dE3 Sculptor Satellite of Milky Way
Andromeda V dSph Andromeda Satellite of the Andromeda Galaxy
Andromeda II dE0 Andromeda Satellite of the Andromeda Galaxy
Fornax Dwarf (E356-G04) dSph/E2 Fornax Satellite of Milky Way
Carina Dwarf (E206-G220) dE3 Carina Satellite of Milky Way
Antlia Dwarf dE3/dSph/Irr? Antlia
Leo I (DDO 74) dE3 Leo Satellite of Milky Way
Sextans Dwarf dE3 Sextans Satellite of Milky Way
Leo II (Leo B) dE0 pec Leo Satellite of Milky Way
Ursa Minor Dwarf dE4 Ursa Minor Satellite of Milky Way
Draco Dwarf (DDO 208) dE0 pec Draco Satellite of Milky Way
SagDSG (Sagittarius Dwarf Spheroidal Galaxy) dSph/E7 Sagittarius Satellite of Milky Way
Tucana Dwarf dE5 Tucana
Cassiopeia Dwarf (Andromeda VII) dSph Cassiopeia Satellite of the Andromeda Galaxy
Pegasus Dwarf Spheroidal Galaxy (Andromeda VI) dSph Pegasus Satellite of the Andromeda Galaxy
Ursa Major I Dwarf and Ursa Major II Dwarf dSph Ursa Major Satellite of Milky Way
Leo IV dSph Leo Satellite of the Milky Way
Leo V dSph Leo Satellite of the Milky Way
Leo T dSph/Irr Leo Satellite of the Milky Way
Boötes II dSph Boötes Satellite of the Milky Way
Boötes III dSph Boötes Satellite of the Milky Way
Coma Berenices dSph Coma Berenices Satellite of the Milky Way
Segue 2 dSph Aries Satellite of the Milky Way
Hercules dSph Hercules Satellite of the Milky Way
Pisces II dSph Pisces Satellite of the Milky Way
Reticulum II dSph Reticulum Satellite of the Milky Way
Eridanus II dSph Eridanus Probable satellite of the Milky Way
Grus dSph Grus Satellite of the Milky Way
Tucana II dSph Tucana Satellite of the Milky Way
Identification unclear
name type constellation notes
Virgo Stellar Stream dSph (remnant)? Virgo In the process of merging with the Milky Way
Willman 1 dSph or Globular Cluster Ursa Major 147,000 light-years away
UGCA 86 (0355+66) Irr, dE or S0 Camelopardalis
UGCA 92 (EGB0427+63) Irr or S0 Camelopardalis
Horologium dSph or Globular Cluster Horologium Satellite of the Milky Way. Not to be confused with the Horologium Supercluster.
Pictoris dSph or Globular Cluster Pictor Satellite of the Milky Way
Phoenix II dSph or Globular Cluster Phoenix Satellite of the Milky Way
Indus dSph or Globular Cluster Indus Satellite of the Milky Way
Eridanus III dSph or Globular Cluster Eridanus Satellite of the Milky Way
Probable non-members
name type constellation notes
GR 8 (DDO 155) Im V Virgo Distance 7.9 million light years[14]
IC 5152 IAB(s)m IV Indus Distance 5.8 million light years, possibly an outlying member of the local group[15]
NGC 55 SB(s)m Sculptor Distance 7.2 million light years[16]
NGC 404 E0 or SA(s)0 Andromeda Distance 10 million light years[17]
Andromeda IV Irr Andromeda Once considered to be associated with M31. Its distance is now known to be 22 to 24 million light years (not close to the Andromeda Galaxy at all).[18]
NGC 1569 Irp+ III-IV Camelopardalis In IC 342 group of galaxies. Distance 11 million light years[19]
NGC 1560 (IC 2062) Sd Camelopardalis Distance 8-12 million light years
Camelopardalis A Irr Camelopardalis
Argo Dwarf Irr Carina
ESO 347-8 (2318–42) Irr Grus
UKS 2323-326 Irr Sculptor
UGC 9128 (DDO 187) Irp+ Boötes
Objects in the Local Group no longer recognised as galaxies
name type constellation notes
Palomar 12 (Capricornus Dwarf) Capricornus Globular cluster formerly classified as a dwarf spheroidal galaxy
Palomar 4 (Ursa Major Dwarf) Ursa Major Globular cluster formerly classified as a dwarf spheroidal galaxy
Palomar 3 (Sextans C) Sculptor Globular cluster formerly classified as a dwarf spheroidal galaxy[20]

Other objects

A diagram of our location in the observable universe. (Alternative image.)
A diagram of our location in the observable universe. (Alternative image.)

See also

References

  1. ^ The mass of the Local Group is essentially accounted for by the mass of the Milky Way and the Andromeda Galaxy. Estimates for the mass of each galaxy are compatible with 1023 M, and Peñarrubia et al. (2014) estimate (2.3±0.7)×1012 M for the Local Group, but Karachentsev and Kashibadze (2006) estimate the somewhat lower value of (1.29±0.14)×1012 M.
  2. ^ a b c Karachentsev, I. D.; Kashibadze, O. G. (2006). "Masses of the local group and of the M81 group estimated from distortions in the local velocity field". Astrophysics. 49 (1): 3–18. Bibcode:2006Ap.....49....3K. doi:10.1007/s10511-006-0002-6.
  3. ^ Kalirai, Jason S.; Beaton, Rachael L.; Geha, Marla C.; Gilbert, Karoline M.; Guhathakurta, Puragra; Kirby, Evan N.; Majewski, Steven R.; Ostheimer, James C.; Patterson, Richard J. (2010-02-17). "THE SPLASH SURVEY: INTERNAL KINEMATICS, CHEMICAL ABUNDANCES, AND MASSES OF THE ANDROMEDA I, II, III, VII, X, AND XIV DWARF SPHEROIDAL GALAXIES". The Astrophysical Journal. 711 (2): 671–692. arXiv:0911.1998. Bibcode:2010ApJ...711..671K. doi:10.1088/0004-637X/711/2/671. ISSN 0004-637X.
  4. ^ Sergey E. Koposov; Vasily Belokurov; Gabriel Torrealba; N. Wyn Evans (10 March 2015). "Beasts of the Southern Wild. Discovery of a large number of Ultra Faint satellites in the vicinity of the Magellanic Clouds". The Astrophysical Journal. 805 (2): 130. arXiv:1503.02079. Bibcode:2015ApJ...805..130K. doi:10.1088/0004-637X/805/2/130.
  5. ^ "The Local Group". NASA's High Energy Astrophysics Science Archive Research Center (HEASARC). NASA. Retrieved 2015-05-05.
  6. ^ Miller, Bryan W.; et al. (December 2001), "The Star Formation History of LGS 3", The Astrophysical Journal, 562 (2): 713–726, arXiv:astro-ph/0108408, Bibcode:2001ApJ...562..713M, doi:10.1086/323853
  7. ^ Kalirai, Jason S.; Beaton, Rachael L.; Geha, Marla C.; Gilbert, Karoline M.; Guhathakurta, Puragra; Kirby, Evan N.; Majewski, Steven R.; Ostheimer, James C.; Patterson, Richard J.; Wolf, Joe (2012). "The observed properties of dwarf galaxies in and around the Local Group". The Astronomical Journal. 144: 4. arXiv:1204.1562. doi:10.1088/0004-6256/144/1/4.
  8. ^ Hubble, E.P. (1936). The realm of the nebulae. Mrs. Hepsa Ely Silliman memorial lectures, 25. New Haven: Yale University Press. ISBN 9780300025002. OCLC 611263346. Archived from the original on 2012-09-29.(pp. 124–151)
  9. ^ van den Bergh, Sidney (May 2003). "History of the Local Group". To be Published In: "The Local Group as an Astrophysical Laboratory": 5042. arXiv:astro-ph/0305042. Bibcode:2003astro.ph..5042V.
  10. ^ Kalirai, Jason S.; Beaton, Rachael L.; Geha, Marla C.; Gilbert, Karoline M.; Guhathakurta, Puragra; Kirby, Evan N.; Majewski, Steven R.; Ostheimer, James C.; Patterson, Richard J.; Wolf, Joe (2018). "Evidence for an Intermediate-Mass Milky Way from Gaia DR2 Halo Globular Cluster Motions". arXiv:1804.11348 [astro-ph.GA].
  11. ^ "The Galaxies of the Local Group".. Kalirai, Jason S.; Beaton, Rachael L.; Geha, Marla C.; Gilbert, Karoline M.; Guhathakurta, Puragra; Kirby, Evan N.; Majewski, Steven R.; Ostheimer, James C.; Patterson, Richard J.; Wolf, Joe (2015). "Rings and Radial Waves in the Disk of the Milky Way". The Astrophysical Journal. 801 (2): 105. arXiv:1503.00257. doi:10.1088/0004-637X/801/2/105.
  12. ^ "A bridge of stars connects two dwarf galaxies". 2017-02-08.
  13. ^ a b van den Bergh, Sidney (April 2000). "Updated Information on the Local Group". The Publications of the Astronomical Society of the Pacific. 112 (770): 529–536. arXiv:astro-ph/0001040. Bibcode:2000PASP..112..529V. doi:10.1086/316548.
  14. ^ Tolstoy, Eline (1999). "Detailed Star-Formation Histories of Nearby Dwarf Irregular Galaxies using HST". In Patricia Whitelock and Russell Cannon (eds.). The stellar content of Local Group galaxies, Proceedings of the 192nd symposium of the International Astronomical Union. The Stellar Content of Local Group Galaxies. 192. Astronomical Society of the Pacific. p. 218. Bibcode:1999IAUS..192..218T. ISBN 978-1886733824.CS1 maint: Uses editors parameter (link)
  15. ^ Ziljstra, A. A.; Minniti, Dante (April 1999). "A Dwarf Irregular Galaxy at the Edge of the Local Group: Stellar Populations and Distance of IC 5152". Astronomical Journal. 117 (4): 1743–1757. arXiv:astro-ph/9812330. Bibcode:1999AJ....117.1743Z. doi:10.1086/300802. Retrieved 2011-03-11.
  16. ^ van de Steene, G. C.; et al. (2006). "Distance determination to NGC 55 from the planetary nebula luminosity function". Astronomy and Astrophysics. 455 (3): 891–896. Bibcode:2006A&A...455..891V. doi:10.1051/0004-6361:20053475.
  17. ^ Jensen, Joseph B.; Tonry, John L.; Barris, Brian J.; Thompson, Rodger I.; et al. (February 2003). "Measuring Distances and Probing the Unresolved Stellar Populations of Galaxies Using Infrared Surface Brightness Fluctuations". Astrophysical Journal. 583 (2): 712–726. arXiv:astro-ph/0210129. Bibcode:2003ApJ...583..712J. doi:10.1086/345430.
  18. ^ Nowakowski, Tomasz (22 December 2015). "Andromeda IV turns out to be a solitary gas-rich dwarf galaxy". physorg. Retrieved 25 December 2015.
  19. ^ Grocholski, Aaron J.; Aloisi, Alessandra; van der Marel, Roeland P.; Mack, Jennifer; et al. (October 20, 2008). "A New Hubble Space Telescope Distance to NGC 1569: Starburst Properties and IC 342 Group Membership". Astrophysical Journal Letters. 686 (2): L79–L82. arXiv:0808.0153. Bibcode:2008ApJ...686L..79G. doi:10.1086/592949.
  20. ^ "Pal3". simbad.u-strasbg.fr. Retrieved 26 August 2017.
  21. ^ Wakker, B. P.; York, D. G.; Wilhelm, R.; Barentine, J. C.; Richter, P.; Beers, T. C.; Ivezić, Ž.; Howk, J. C. (2008). "Distances to Galactic High‐Velocity Clouds. I. Cohen Stream, Complex GCP, Cloud g1". The Astrophysical Journal. 672 (1): 298–319. arXiv:0709.1926. Bibcode:2008ApJ...672..298W. doi:10.1086/523845.
  22. ^ "Massive Gas Cloud Speeding Toward Collision With Milky Way". Retrieved 2008-06-06.

External links

Andromeda Galaxy

The Andromeda Galaxy (), also known as Messier 31, M31, or NGC 224, is a spiral galaxy approximately 780 kiloparsecs (2.5 million light-years) from Earth, and the nearest major galaxy to the Milky Way. Its name stems from the area of the Earth's sky in which it appears, the constellation of Andromeda.

The virial mass of the Andromeda Galaxy is of the same order of magnitude as that of the Milky Way, at a trillion solar masses (1012M☉). The mass of either galaxy is difficult to estimate with any accuracy, but it was long thought that the Andromeda Galaxy is more massive than the Milky Way by a margin of some 25% to 50%. This has been called into question by a 2018 study which cited a lower estimate on the mass of the Andromeda Galaxy,

combined with preliminary reports on a 2019 study estimating a higher mass of the Milky Way.

The Andromeda Galaxy has a diameter of about 220,000 light-years, making it the largest member of the Local Group at least in terms of extension, if not mass.

The number of stars contained in the Andromeda Galaxy is estimated at one trillion (1×1012), or roughly twice the number estimated for the Milky Way.The Milky Way and Andromeda galaxies are expected to collide in ~4.5 billion years, merging to form a giant elliptical galaxy or a large lenticular galaxy.

With an apparent magnitude of 3.4, the Andromeda Galaxy is among the brightest of the Messier objects making it visible to the naked eye from Earth on moonless nights, even when viewed from areas with moderate light pollution.

Andromeda V

Andromeda V is a dwarf spheroidal galaxy about 2.52 Mly away in the constellation Andromeda.Andromeda V was discovered by Armandroff et al. and published in 1998 after their analysis of the digitized version of the second Palomar Sky Survey.The metallicity of Andromeda V is above the average metallicity to luminosity ratio of the Local Group's dwarf galaxies.

Andromeda XI

Andromeda XI (And 11) is a dwarf spheroidal galaxy about 2.6 million light-years away from the Sun in the constellation Andromeda. Discovered in 2006, And XI is a satellite galaxy of the Andromeda Galaxy (M31).

Andromeda–Milky Way collision

The Andromeda–Milky Way collision is a galactic collision predicted to occur in about 3.75 billion years between two galaxies in the Local Group—the Milky Way (which contains the Solar System and Earth) and the Andromeda Galaxy. The stars involved are sufficiently far apart that it is improbable that any of them will individually collide. Some stars will be ejected from the resulting galaxy, nicknamed Milkomeda or Milkdromeda.

Aquarius Dwarf

The Aquarius Dwarf is a dwarf irregular galaxy, first catalogued in 1959 by the DDO survey. It is located within the boundaries of the constellation of Aquarius. It is a member of the Local Group of galaxies, albeit an extremely isolated one; it is one of only a few known Local Group members for which a past close approach to the Milky Way or Andromeda galaxy can be ruled out, based on its current location and velocity.

Local Group membership was firmly established only in 1999, with the derivation of a distance based on the tip of the red-giant branch method. Its distance from the Milky Way of 3.2 ±0.2 Mly (980 ±40 kpc) means that Aquarius Dwarf is quite isolated in space. It is one of the least luminous Local Group galaxies to contain significant amounts of neutral hydrogen and support to ongoing star formation, although it does so only at an extremely low level.

Because of its large distance, the Hubble Space Telescope is required in order to study its stellar populations in detail. RR Lyrae stars have been discovered in Aquarius Dwarf, indicating the existence of stars more than 10 billion years old, but the majority of its stars are much younger (median age 6.8 billion years). Among Local Group galaxies, only Leo A has a younger mean age, leading to the suggestion that delayed star formation could be correlated with galaxy isolation.

Chiricahua

Chiricahua ( CHIRR-i-KAH-wə) are a band of Apache Native Americans, based in the Southern Plains and Southwest United States. Culturally related to other Apache peoples, Chiricahua historically shared a common area, language, customs, and intertwined family relations. At the time of European contact, they had a territory of 15 million acres (61,000 km2) in Southwestern New Mexico and Southeastern Arizona in the United States and in Northern Sonora and Chihuahua in Mexico.

Today Chiricahua are enrolled in two federally recognized tribes in the United States: the Fort Sill Apache Tribe, located near Apache, Oklahoma with a small reservation outside Deming, New Mexico, and the Mescalero Apache Tribe of the Mescalero Reservation near Ruidoso, New Mexico. The San Carlos Apache Tribe, Arizona does have Chiricahua Apache people there also.

Galaxy group

A galaxy group or group of galaxies (GrG) is an aggregation of galaxies comprising about 50 or fewer gravitationally bound members, each at least as luminous as the Milky Way (about 1010 times the luminosity of the Sun); collections of galaxies larger than groups that are first-order clustering are called galaxy clusters. The groups and clusters of galaxies can themselves be clustered, into superclusters of galaxies.

The Milky Way galaxy is part of a group of galaxies called the Local Group.

Group Policy

Group Policy is a feature of the Microsoft Windows NT family of operating systems that controls the working environment of user accounts and computer accounts. Group Policy provides centralized management and configuration of operating systems, applications, and users' settings in an Active Directory environment. A set of Group Policy configurations is called a Group Policy Object (GPO). A version of Group Policy called Local Group Policy (LGPO or LocalGPO) allows Group Policy Object management without Active Directory on standalone computers.

Large Magellanic Cloud

The Large Magellanic Cloud (LMC) is a satellite galaxy of the Milky Way. At a distance of about 50 kiloparsecs (≈163,000 light-years), the LMC is the second- or third-closest galaxy to the Milky Way, after the Sagittarius Dwarf Spheroidal (~16 kpc) and the possible dwarf irregular galaxy known as the Canis Major Overdensity. Based on readily visible stars and a mass of approximately 10 billion solar masses, the diameter of the LMC is about 14,000 light-years (4.3 kpc), making it roughly one one-hundredth as massive as the Milky Way. This makes the LMC the fourth-largest galaxy in the Local Group, after the Andromeda Galaxy (M31), the Milky Way, and the Triangulum Galaxy (M33).

The LMC is classified as a Magellanic spiral. It contains a stellar bar that is geometrically off-center, suggesting that it was a barred dwarf spiral galaxy before its spiral arms were disrupted, likely by tidal interactions from the Small Magellanic Cloud (SMC), and the Milky Way's gravity.With a declination of about -70°, the LMC is visible as a faint "cloud" only in the southern celestial hemisphere and from latitudes south of 20° N, straddling the border between the constellations of Dorado and Mensa, and appears longer than 20 times the Moon's diameter (about 10° across) from dark sites away from light pollution.The Milky Way and the LMC are expected to collide in approximately 2.4 billion years.

List of nearest galaxies

This is a list of known galaxies within 3.59 megaparsecs (11.7 million light-years) of the Solar System, in ascending order of distance.

This encompasses all of the about 50 Local Group galaxies, and some that are members of neighboring galaxy groups, the M81 Group and the Centaurus A/M83 Group, and some that are currently not in any defined galaxy group.

The list aims to reflect current knowledge: not all galaxies within the 3.59 Mpc radius have been discovered. Nearby dwarf galaxies are still being discovered, and galaxies located behind the central plane of the Milky Way are extremely difficult to discern. It is possible for any galaxy to mask another located beyond it.

Intergalactic distance measurements are subject to large uncertainties. Figures listed are composites of many measurements, some of which may have had their individual error bars tightened to the point of no longer overlapping with each other.

Local Sheet

The Local Sheet in astronomy is a nearby extragalactic region of space where the Milky Way, the members of the Local Group and other galaxies share a similar peculiar velocity. This region lies within a radius of about 7 Mpc (23 Mly), 0.46 Mpc (1.5 Mly) thick, and galaxies beyond that distance show markedly different velocities. The Local Group has only a relatively small peculiar velocity of 66 km⋅s−1 with respect to the Local Sheet. Typical velocity dispersion of galaxies is only 40 km⋅s−1 in the radial direction. Nearly all nearby bright galaxies belong to the Local Sheet. The Local Sheet is part of the Local Volume and is in the Virgo Supercluster (Local Supercluster). The Local Sheet forms a wall of galaxies delineating one boundary of the Local Void.A significant component of the mean velocity of the galaxies in the Local Sheet appears as the result of the gravitational attraction of the Virgo Cluster of galaxies, resulting in a peculiar motion ~185 km⋅s−1 toward the cluster. A second component is directed away from the center of the Local Void; an expanding region of space spanning an estimated 45 Mpc (150 Mly) that is only sparsely populated with galaxies. This component has a velocity of 259 km⋅s−1. The Local Sheet is inclined 8° from the Local Supercluster (Virgo Supercluster).The so-called Council of Giants is a ring of twelve large galaxies surrounding the Local Group in the Local Sheet, with a radius of 3.75 Mpc (12.2 Mly). Ten of these are spirals, while the remaining two are ellipticals. The two ellipticals (Maffei 1 and Centaurus A) lie on opposite sides of the Local Group, and their formation may have prompted the development of the Local Group. The Local Sheet's own development outlines a concentration of dark matter in a filament.

* The mass is given as the logarithm of the mass in solar masses.

Messier 110

Messier 110 or M110, also known as NGC 205, is a dwarf elliptical galaxy that is a satellite of the Andromeda Galaxy. Although Charles Messier never included the galaxy in his list, it was depicted by him, together with M32, on a drawing of the Andromeda galaxy; a label on the drawing indicates that Messier first observed NGC 205 on August 10, 1773. The galaxy was independently discovered by Caroline Herschel on August 27, 1783; her brother William Herschel described her discovery in 1785. The suggestion to assign the galaxy a Messier number was made by Kenneth Glyn Jones in 1967.This galaxy has a morphological classification of pec dE5, indicating a dwarf elliptical galaxy with a flattening of 50%. M110 is designated peculiar because there are patches of dust and young blue stars located near the center. This is unusual for dwarf elliptical galaxies in general, and the reason for this peculiarity is unclear. Unlike M32, NGC 205 does not (as of 2005) show evidence for a supermassive black hole at its center.The interstellar dust in M110 has a mass of (1.1–1.8)×104 M☉ with a temperature of 18–22 K, and the interstellar gas has (4–7)×106 M☉. The inner regions of M110 show a deficiency in the interstellar medium (IM) materials, which most likely were ejected by supernova explosions. Tidal interactions with M31 may have stripped away a significant fraction of the expelled gas and dust, leaving the galaxy as a whole deficient in its IM density.A few novae have been detected in this galaxy, including one discovered

in 1999 by Johnson and Modjaz, and another detected in 2002, by Nakano and Sumoto. The latter, designated EQ J004015.8+414420, had also been captured in images taken by the Sloan Digital Sky Survey (SDSS) in October, 2002.About half of the Andromeda's satellite galaxies are orbiting the host galaxy along a highly flattened plane, with 14 out of 16 following the same sense of rotation. One theory proposes that these objects once belonged to a subhalo surrounding NGC 205, then the group was broken up by tidal forces during a close encounter with Andromeda.

Messier 32

Messier 32 (also known as M32 and NGC 221) is a dwarf "early-type" galaxy located about 2.65 million light-years from Earth, appearing in the constellation Andromeda. M32 is a satellite galaxy of the Andromeda Galaxy (M31) and was discovered by Guillaume Le Gentil in 1749. M32 measures 6.5 ± 0.2 thousand light-years in diameter at the widest point.The galaxy is a prototype of the relatively rare, compact elliptical (cE) galaxy class.

Half the stars concentrate within an effective radius of only 100 parsecs.

Densities in the central stellar cusp increase steeply, exceeding 3×107 M⊙ pc−3 at the smallest radii resolved by HST, and the half-light radius of this central star cluster is around 6 parsec.

Like more ordinary elliptical galaxies, M32 contains mostly older faint red and yellow stars with practically no dust or gas and consequently no current star formation. It does, however, show hints of star formation in the relatively recent past.

NGC 147

NGC 147 (also known as DDO3 or Caldwell 17) is a dwarf spheroidal galaxy about 2.58 Mly away in the constellation Cassiopeia. NGC 147 is a member of the Local group of galaxies and a satellite galaxy of the Andromeda Galaxy (M31). It forms a physical pair with the nearby galaxy NGC 185,

another remote satellite of M31. It was discovered by John Herschel in September 1829. Visually it is both fainter and slightly larger than NGC 185 (and therefore has a considerably lower surface brightness). This means that NGC 147 is more difficult to see than NGC 185, which is visible in small telescopes. In the Webb Society Deep-Sky Observer's Handbook, the visual appearance of NGC 147 is described as follows:

Large, quite faint, irregularly round; it brightens in the middle to a stellar nucleus.

The membership of NGC 147 in the Local Group was confirmed by Walter Baade in 1944 when he was able to resolve the galaxy into individual stars with the 100-inch (2.5 m) telescope at Mount Wilson near Los Angeles.

NGC 185

NGC 185 (also known as Caldwell 18) is a dwarf spheroidal galaxy located 2.08 million light-years from Earth, appearing in the constellation Cassiopeia. It is a member of the Local Group, and is a satellite of the Andromeda Galaxy (M31). NGC 185 was discovered by William Herschel on November 30, 1787, and he cataloged it "H II.707". John Herschel observed the object again in 1833 when he cataloged it as "h 35", and then in 1864 when he cataloged it as "GC 90" within his General Catalogue of Nebulae and Clusters. NGC 185 was first photographed between 1898 and 1900 by James Edward Keeler with the Crossley Reflector of Lick Observatory. Unlike most dwarf elliptical galaxies, NGC 185 contains young stellar clusters, and star formation proceeded at a low rate until the recent past. NGC 185 has an active galactic nucleus (AGN) and is usually classified as a type 2 Seyfert galaxy, though its status as a Seyfert is questioned. It is possibly the closest Seyfert galaxy to Earth, and is the only known Seyfert in the Local Group.

Supercluster

A supercluster is a large group of smaller galaxy clusters or galaxy groups; it is among the largest-known structures of the cosmos. The Milky Way is part of the Local Group galaxy group (which contains more than 54 galaxies), which in turn is part of the Virgo Cluster, which is part of the Laniakea Supercluster. This supercluster spans over 500 million light-years, while the Local Group spans over 10 million light-years. The large size and low density of superclusters means they, unlike clusters, expand with the Hubble expansion. The number of superclusters in the observable universe is estimated to be 10 million.

Triangulum Galaxy

The Triangulum Galaxy is a spiral galaxy approximately 3 million light-years (ly) from Earth in the constellation Triangulum. It is catalogued as Messier 33 or NGC 598. The Triangulum Galaxy is the third-largest member of the Local Group of galaxies, behind the Milky Way and the Andromeda Galaxy. It is one of the most distant permanent objects that can be viewed with the naked eye.

The galaxy is the smallest spiral galaxy in the Local Group and it is believed to be a satellite of the Andromeda Galaxy due to their interactions, velocities, and proximity to one another in the night sky. It also has an H II nucleus.

Virgo Cluster

The Virgo Cluster is a cluster of galaxies whose center is 53.8 ± 0.3 Mly (16.5 ± 0.1 Mpc)

away in the constellation Virgo. Comprising approximately 1300 (and possibly up to 2000) member galaxies, the cluster forms the heart of the larger Virgo Supercluster, of which the Local Group (containing our Milky Way galaxy) is a member. The Local Group actually experiences the mass of the Virgo Supercluster as the Virgocentric flow. It is estimated that the Virgo Cluster's mass is 1.2×1015 M☉ out to 8 degrees of the cluster's center or a radius of about 2.2 Mpc.Many of the brighter galaxies in this cluster, including the giant elliptical galaxy Messier 87, were discovered in the late 1770s and early 1780s and subsequently included in Charles Messier's catalogue of non-cometary fuzzy objects. Described by Messier as nebulae without stars, their true nature was not recognized until the 1920s.The cluster subtends a maximum arc of approximately 8 degrees centered in the constellation Virgo. Although some of the cluster's most prominent members can be seen with smaller instruments, a 6-inch telescope will reveal about 160 of the cluster's galaxies on a clear night. Its brightest member is the elliptical galaxy Messier 49; however its most famous member is the elliptical galaxy Messier 87, which is located in the center of the cluster.

Virgo Supercluster

The Virgo Supercluster (Virgo SC) or the Local Supercluster (LSC or LS) is a mass concentration of galaxies containing the Virgo Cluster and Local Group, which in turn contains the Milky Way and Andromeda galaxies. At least 100 galaxy groups and clusters are located within its diameter of 33 megaparsecs (110 million light-years). The Virgo SC is one of about 10 million superclusters in the observable universe and is in the Pisces–Cetus Supercluster Complex, a galaxy filament.

A 2014 study indicates that the Virgo Supercluster is only a lobe of an even greater supercluster, Laniakea, a larger, competing referent of Local Supercluster centered on the Great Attractor.

Location
Galactic core
Spiral arms
Satellite galaxies
Related
Location
Satellite galaxies
Catalogued stars
Other
Location
H II regions
Suspected satellite galaxies
Other
Included
Related

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