List of galaxies
List of galaxies
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List of galaxies

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Size (left) and distance (right) of a few well-known galaxies put to scale

An estimated 2 trillion+ galaxies occupy the observable universe.[1] On the order of 100,000 galaxies make up the Local Supercluster, and about 51 galaxies are in the Local Group (see list of nearest galaxies for a complete list).

The first attempts at systematic catalogues of galaxies were made in the 1960s, with the Catalogue of Galaxies and Clusters of Galaxies listing 29,418 galaxies and galaxy clusters, and with the Morphological Catalogue of Galaxies, a putatively complete list of galaxies with photographic magnitude above 15, listing 30,642. In the 1980s, the Lyons Groups of Galaxies listed 485 galaxy groups with 3,933 member galaxies. Galaxy Zoo is a project aiming at a more comprehensive list: launched in July 2007, it has classified over one million galaxy images from The Sloan Digital Sky Survey, The Hubble Space Telescope and the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey.[2]

Named galaxies

[edit]

This is a list of galaxies that are well known by something other than an entry in a catalog or list, or a set of coordinates, or a systematic designation.

Image Galaxy Constellation Origin of name Notes
False-colour image showing Alcyoneus with LOFAR radio data at 144 MHz (orange) and WISE infrared data at 3.4 micron (blue) overlaid.
 Alcyoneus Lynx A low-exitation, Fanaroff and Riley Class II radio galaxy, one of the largest discovered.
Andromeda I Andromeda Andromeda I was named because the galaxy is 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.
Andromeda Galaxy Andromeda Andromeda, which is shortened from "Andromeda Galaxy", gets its name from the area of the sky in which it appears, the constellation of Andromeda.[citation needed] Andromeda is the closest big galaxy to the Milky Way and is expected to collide with the Milky Way around 4.5 billion years from now. The two will eventually merge into a single new galaxy called Milkdromeda[3] According to simulations, this object would probably be a giant elliptical galaxy, but with a centre showing less stellar density than current elliptical galaxies.[4]
Ambartsumian's Knot Ursa Major Appearance is similar to Ambartsumian's knot NGC 3561, also known as Arp 105, is a pair of interacting galaxies NGC 3561A and NGC 3561B within the galaxy cluster Abell 1185 in Ursa Major. It was discovered by British astronomer John Herschel on 30 March 1827.[6] Its common name is "the Guitar" and contains a small tidal dwarf galaxy known as Ambartsumian's Knot that is believed to be the remnant of the extensive tidal tail pulled out of one of the galaxies.
Antennae Galaxies Corvus Appearance is similar to an insect's antennae.[citation needed] Two colliding galaxies[5]
Backward Galaxy Centaurus It appears to rotate backwards, as the tips of the spiral arms point in the direction of rotation.[citation needed]
Barnard's Galaxy Named after Edward Emerson Barnard.[citation needed]
Bear Paw Galaxy Lynx It resembles the appearance of a bear's claw.[citation needed] Also known as "Bear Claw Galaxy."[citation needed]
Black Eye Galaxy Coma Berenices It has a spectacular dark band of absorbing dust in front of the galaxy's bright nucleus, giving rise to its nicknames of the "Black Eye" or "Evil Eye" galaxy.[6] Also known as "Sleeping Beauty Galaxy."
Blinking Galaxy Serpens Its difficulty of viewing in a small telescope and tendency to go in and out of view.[citation needed]
Bode's Galaxy Ursa Major Named for Johann Elert Bode who discovered this galaxy in 1774.[7] Also known as Messier 81. The largest galaxy in the M81 Group. It harbors a supermassive black hole 70 million times the mass of the Sun.
Butterfly Galaxies Virgo Looks are similar to a butterfly.[8]
Cartwheel Galaxy Sculptor Its visual appearance is similar to that of a spoked cartwheel.[citation needed] The largest in the Cartwheel Galaxy group, made up of four spiral galaxies[citation needed]
Cigar Galaxy Ursa Major Appears similar in shape to a cigar.[citation needed] Also known as Messier 82 or M82[citation needed]
Circinus Galaxy Circinus Named after the constellation it is located in (Circinus).[citation needed]
Cocoon Galaxy Canes Venatici Its resemblance in shape to a cocoon[citation needed]
Coma Pinwheel Galaxy Coma Berenices Named after its resemblance to the Pinwheel Galaxy and its location in the Coma Berenices constellation.[citation needed] Also known as Messier 99 or M99[citation needed]
Comet Galaxy Sculptor This galaxy is named after its unusual appearance, looking like a comet.[citation needed] The comet effect is caused by tidal stripping by its galaxy cluster, Abell 2667.[citation needed]
Condor Galaxy Pavo Named after a condor, a type of vulture that is one of the largest flying birds.[citation needed] The largest known spiral galaxy, it has a diameter of over 665,300 light-years (204.0 kiloparsecs).[9] It is tidally disturbed by the smaller lenticular galaxy IC 4970.[10]
Cosmos Redshift 7 Sextans The name of this galaxy is based on a Redshift (z) measurement of nearly 7 (actually, z = 6.604).[11] Galaxy Cosmos Redshift 7 is reported to be the brightest of distant galaxies (z > 6) and to contain some of the earliest first stars (first generation; Population III) that produced the chemical elements needed for the later formation of planets and life as we know it.[11]
Dusty Hand Galaxy Camelopardalis Named after the dust lanes and spiral arms of the galaxy.[citation needed]
Eye of God Eridanus Named after its structural appearance[citation needed] A prototype for multi-arm spiral galaxies[citation needed]
Eye of Sauron Canes Venatici Due to its resemblance to the Eye of Sauron from The Lord of the Rings.[12]
Fireworks Galaxy Cygnus and Cepheus Due to its bright and spotty appearance[citation needed] Active starburst galaxy[citation needed]
Fried Egg Galaxy Pegasus Due to its similar appearance to a fried egg[citation needed]
Godzilla Galaxy Perseus Its extremely large size[13]
Helix Galaxy Ursa Major Its shape resembles a helix[citation needed]
Grasshopper Lynx Named after its appearance to a grasshopper[14] Two colliding galaxies
Hidden Galaxy Camelopardalis The difficulty in observing this object makes it 'hidden'[15][16] though it can readily be detected even with binoculars.[17]
Hockey Stick Galaxies Canes Venatici Its elongated and curved appearance resembles a hockey stick.[citation needed] Also known as Crowbar Galaxy[citation needed]
Hoag's Object Serpens Caput This is named after Art Hoag, who discovered this ring galaxy.[citation needed] It is of the subtype Hoag-type galaxy, and may in fact be a polar-ring galaxy with the ring in the plane of rotation of the central object.[citation needed]
Knife Edge Galaxy Draco Named after its thin shape, similar to knife's edge.[citation needed]
Large Magellanic Cloud Dorado/Mensa Named after Ferdinand Magellan[citation needed] This is the fourth-largest galaxy in the Local Group, and forms a pair with the SMC, and from recent research, may not be part of the Milky Way system of satellites at all.[18]
Lindsay-Shapley Ring Volans Named after its discoverer, Eric Lindsay, his professor Harlow Shapley, and its nature as a ring galaxy.[citation needed] The ring is the result of collision with another galaxy[citation needed]
Little Sombrero Galaxy Pegasus Named after its similarity to the Sombrero Galaxy.[citation needed]
Malin 1 Coma Berenices Discovered and named by David Malin.[19]
Meathook Galaxy Volans After its appearance resembling a meathook.[20]
Medusa Merger Ursa Major Ejected dust from the merging galaxies is said to look like the snakes that the Gorgon Medusa from Greek mythology had on her head.[citation needed]
Sculptor Dwarf Galaxy Sculptor Similar to the Sculpture Galaxies[citation needed] Also known as Sculptor Dwarf Elliptical Galaxy, Sculptor Dwarf Spheroidal Galaxy, and formerly as the Sculptor System[citation needed]
Mice Galaxies Coma Berenices Appearance is similar to a mouse.[citation needed]
Small Magellanic Cloud Tucana Named after Ferdinand Magellan[citation needed] This forms a pair with the LMC, and from recent research, may not be part of the Milky Way system of satellites at all.[citation needed]
Mayall's Object Ursa Major This is named after Nicholas Mayall, of the Lick Observatory, who discovered it.[21][22][23] Also called VV 32 and Arp 148, this is a very peculiar looking object, and is likely to be not one galaxy, but two galaxies undergoing a collision. Event in images is a spindle shape and a ring shape.[citation needed]
Milky Way Sagittarius (centre) The appearance from Earth of the galaxy—a band of light[citation needed] The galaxy containing the Sun and its Solar System, and therefore Earth.
Needle Galaxy Coma Berenices Named due to its slender appearance.[citation needed] Also known as Caldwell 38[citation needed]
Wolf-Lundmark-Melotte Cetus Named for the three astronomers instrumental in its discovery and identification.[citation needed]
Paramecium Galaxy Pegasus Named after its appearance to the organism Paramecium It is included in the Atlas of Peculiar Galaxies in the category galaxies with detached segments.
Peekaboo Galaxy Hydra Galaxy (aka HIPASS J1131-31) was hidden behind a relatively fast-moving foreground star (TYC 7215–199–1) and became observable when the star moved aside.[citation needed] Galaxy, relatively nearby, is considered one of the most metal-poor ("extremely metal-poor" (XMP)), least chemically enriched, and seemingly primordial, galaxies known.[24][25]
Pinwheel Galaxy Ursa Major Similar in appearance to a pinwheel.[citation needed] Also known as Messier 101 or M101[citation needed]
Radio image of Porphyrion, a black hole jet system spanning an estimated 23 million light-years.
 Porphyrion Draco
Porpoise Galaxy Hydra Its appearance resembles a porpoise[26] Also known as the Penguin Galaxy
Sculptor Galaxy Sculptor Named after its location in the Sculptor Constellation. Also called the Silver Dollar or Silver Coin Galaxy, because of its light and circular appearance.[citation needed] Also known as the Silver Coin, Silver Dollar Galaxy or Caldwell 65[citation needed]
Sculptor Pinwheel Galaxy Sculptor Named after its resemblance to a pinwheel and its location in the Sculptor Constellation. [citation needed] Also known as NGC 300 and Caldwell 70.
Skyrocket Galaxy Ursa Major Its resemblance to a July 4th skyrocket[citation needed]
Sombrero Galaxy Virgo Similar in appearance to a sombrero.[27] Also known as Messier Object 104 or M104
Southern Pinwheel Galaxy Hydra Named after its resemblance to the Pinwheel Galaxy and its location in the southern celestial hemisphere.[citation needed]
Spider Galaxy Boötes Named after its appearance of a spider[citation needed]
Spiderweb Galaxy Hydra Its irregular shape and continuous structure resembles a spiderweb.[28]
Starfish Galaxy Ophiuchus Similar in appearance to a starfish.[citation needed] Merger of 3 galaxies[citation needed]
Sunflower Galaxy Canes Venatici Similar in appearance to a sunflower.[citation needed]
Surfboard Galaxy Ursa Major Similar in appearance to a surfboard. [citation needed] Also known as Messier 108 or M108.
Tadpole Galaxy Draco The name comes from the resemblance of the galaxy to a tadpole.[29] This shape resulted from tidal interaction that drew out a long tidal tail.
Topsy Turvy Galaxy Reticulum The disorganized and chaotic appearance makes it look topsy turvy.[30]
Triangulum Galaxy Triangulum Named after its location within the Triangulum constellation.[citation needed]
UFO Galaxy Lynx Named after its resemblance to a UFO.[31]
Whale Galaxy Canes Venatici Named after its supposed resemblance to a whale.[citation needed]
Whirlpool Galaxy Canes Venatici From the whirlpool appearance this gravitationally disturbed galaxy exhibits.[citation needed]

Naked-eye galaxies

[edit]

This is a list of galaxies that are visible to the naked eye, for at the very least, keen-eyed observers in a very dark-sky environment that is high in altitude, during clear and stable weather.

Naked-eye galaxies
Galaxy Apparent
Magnitude 		Distance Constellation Notes
Milky Way −6.5[a] 0 Sagittarius (centre) This is the galaxy containing the Sun and its Solar System, and therefore Earth. Most things visible to the naked eye in the sky are part of it, including the Milky Way composing the Zone of Avoidance.[32]
Large Magellanic Cloud 0.9 160 kly (49 kpc) Dorado/Mensa Visible only from the southern hemisphere. It is also the brightest patch of nebulosity in the sky.[32][33][34]
Small Magellanic Cloud (NGC 292) 2.7 200 kly (61 kpc) Tucana Visible only from the southern hemisphere.[32][35]
Andromeda Galaxy (M31, NGC 224) 3.4 2.5 Mly (770 kpc) Andromeda Once called the Great Andromeda Nebula, it is situated in the Andromeda constellation.[32][36]
Triangulum Galaxy (M33, NGC 598) 5.7 2.9 Mly (890 kpc) Triangulum Being a diffuse object, its visibility is strongly affected by even small amounts of light pollution, ranging from easily visible in direct vision in truly dark skies to a difficult averted vision object in rural/suburban skies.[37]
Centaurus A (NGC 5128) 6.84 13.7 Mly (4.2 Mpc) Centaurus Centaurus A has been spotted with the naked eye by Stephen James O'Meara.[38]
Bode's Galaxy (M81, NGC 3031) 6.94 12 Mly (3.7 Mpc) Ursa Major Highly experienced amateur astronomers may be able to see Messier 81 under exceptional observing conditions.[39][40][41]

Observational firsts

[edit]
First Galaxy Constellation Year Notes
First spiral galaxy Whirlpool Galaxy Canes Venatici 1845 Lord William Parsons, Earl of Rosse discovered the first spiral nebula from observing M51 (recognition of the spiral shape without the recognition of the object as outside the Milky Way).[42]
Notion of galaxy Milky Way
& Andromeda Galaxy 		Sagittarius (centre)
& Andromeda 		1923 Recognition of the Milky Way and the Andromeda nebula as two separate galaxies by Edwin Hubble.[citation needed]
First Seyfert galaxy NGC 1068 (M77) Cetus 1943
(1908) 		The characteristics of Seyfert galaxies were first observed in M77 in 1908; however, Seyferts were defined as a class in 1943.[43]
First radio galaxy Cygnus A Cygnus 1951 Of several items, then called radio stars, Cygnus A was identified with a distant galaxy, being the first of many radio stars to become a radio galaxy.[44][45]
First quasar 3C 273 Virgo 1962 3C273 was the first quasar with its redshift determined, and by some considered the first quasar.[citation needed]
3C 48 Triangulum 1960 3C48 was the first "radio-star" with an unreadable spectrum, and by others considered the first quasar.[citation needed]
First superluminal galactic jet 3C 279 Virgo 1971 The jet is emitted by a quasar[citation needed]
First low surface brightness galaxy Malin 1 Coma Berenices 1986 Malin 1 was the first verified LSB galaxy. LSB galaxies had been first theorized in 1976.[46]
First superluminal jet from a Seyfert III Zw 2 Pisces[47] 2000 [48]

Prototypes

[edit]

This is a list of galaxies that became prototypes for a class of galaxies.

Prototype Galaxies
Class Galaxy Constellation Date Notes
BL Lac object BL Lacertae (BL Lac) Lacerta This AGN was originally catalogued as a variable star, and "stars" of its type are considered BL Lac objects.
Hoag-type Galaxy Hoag's Object Serpens Caput This is the prototype Hoag-type ring galaxy
Giant LSB galaxy Malin 1 Coma Berenices 1986 [49]
FR II radio galaxy
(double-lobed radio galaxy) 		Cygnus A Cygnus 1951 [50]
Starburst galaxy Cigar Galaxy Ursa Major
Flocculent spiral galaxy NGC 2841 Ursa Major

Closest and most distant-known galaxies by type

[edit]
Title Galaxy Constellation Distance Notes
Closest galaxy Ursa Major III Ursa Major 32,600 light-years
(10 kiloparsecs) 		A proposed dwarf galaxy known as the Canis Major Overdensity may lie closer at 25,000 light-years, however its status as a galaxy is disputed.[51][52][53]
Most distant galaxy MoM-z14 Sextans z=14.44 Existed 280 million years after the Big Bang.[54]
Closest quasar Markarian 231 Ursa Major z=0.0415 Sometimes classified as a Type-2 Seyfert galaxy, though mostly considered to be the nearest quasar.[citation needed]
Most distant quasar UHZ1 Sculptor z=10.1 Gravitationally lensed quasar behind Pandora's Cluster (Abell 2744). It is also the first quasar observed beyond a redshift of 10.[55][56]
Closest radio galaxy Centaurus A (NGC 5128, PKS 1322–427) Centaurus 13.7 Mly [57]
Most distant radio galaxy ILT J2336+1842 Pegasus z=6.6[58] Another radio galaxy, GLEAM J0917-0012, may either lie at z=2.01 or as distant as z=8.21.[59]
Closest Seyfert galaxy Circinus Galaxy Circinus 13 Mly Closest undisputed Seyfert galaxy. It has been proposed that the nearby (2.05 Mly) dwarf galaxy NGC 185 may also be a Seyfert,[60] though this status has been disputed.[61]
Most distant Seyfert galaxy HSC 0921+0007 Hydra z=6.56[62] Seyfert 1 galaxy; also a low-luminosity quasar.[citation needed]
Closest blazar Markarian 421 (Mrk 421, Mkn 421, PKS 1101+384, LEDA 33452) Ursa Major z=0.030 This is a BL Lac object.[63][64]
Most distant-known blazar Q0906+6930 Ursa Major z=5.47 This is a flat spectrum radio-loud quasar-type blazar.[65][66]
Closest BL Lac object Centaurus A Centaurus 13.7 Mly Misaligned BL Lac nucleus.[67] Also the closest radio galaxy (see above)
Most distant BL Lac object FIRST J233153.20+112952.11 Pegasus z=6.57 [68]
Closest LINER
Most distant LINER z=
Closest LIRG
Most distant LIRG z=
Closest ULIRG IC 1127 (Arp 220/APG 220) Serpens Caput z=0.018 [69]
Most distant ULIRG z=
Closest starburst galaxy IC 10 (UGC 192, PGC 1305) Cassiopeia 750 ± 150 kpc (2,450,000 ± 489,000 ly) A mild starburst galaxy, this is the only such galaxy within the Local Group.[70][71]
Most distant starburst galaxy SPT 0243-49 Horologium z=5.698 [72][73]
Most distant spiral galaxy Zhúlóng Sextans z=5.2 [74]
Closest jellyfish galaxy IC 3418 Virgo 17 Mpc [75]
Most distant jellyfish galaxy COSMOS2020-635829 Sextans z=1.156 A candidate jellyfish galaxy.[76]

Closest galaxies

[edit]
See also: List of nearest galaxies
5 Closest Galaxies
Rank Galaxy Distance Notes
1 Milky Way Galaxy 0 This is the galaxy containing the Sun and its Solar System, and therefore Earth.
2 Ursa Major III 0.032 Mly
3 Sagittarius Dwarf Spheroidal Galaxy 0.081 Mly
4 Large Magellanic Cloud 0.163 Mly Largest satellite galaxy of the Milky Way[citation needed]
5 Small Magellanic Cloud 0.197 Mly
  • Mly represents millions of light-years, a measure of distance.
  • Distances are measured from Earth, with Earth being at zero.
Nearest Galaxies by Type
Title Galaxy Date Distance Notes
Nearest galaxy Milky Way always 0 This is the galaxy containing the Sun and its Solar System, and therefore Earth.[citation needed]
Nearest galaxy to the Milky Way Sagittarius Dwarf Spheroidal Galaxy 1994 0.070 Mly The closest, undisputed galaxy. The disputed dwarf galaxy Canis Major Overdensity is even closer at 25,000 light-years.[citation needed]
Nearest dwarf galaxy Sagittarius Dwarf Spheroidal Galaxy 1994 0.070 Mly
Nearest major galaxy to the Milky Way Andromeda Galaxy always 2.54 Mly First identified as a separate galaxy in 1923[citation needed]
Nearest giant galaxy Maffei 1 1967 11 Mly Nearest major elliptical galaxy to the Milky Way[citation needed]
Nearest Neighboring Galaxy Title-holder
Galaxy Date Distance Notes
Ursa Major III 2023 0.01 Mly
Sagittarius Dwarf Spheroidal Galaxy 1994–2023 0.026 Mly
Large Magellanic Cloud antiquity–1994 0.163 Mly This is the upper bound, as it is the nearest galaxy observable with the naked eye.[citation needed]
Small Magellanic Cloud 1913–1914 0.197 Mly This was the first intergalactic distance measured. In 1913, Ejnar Hertzsprung measured the distance to SMC using Cepheid variables. In 1914, he did it for LMC.[citation needed]
Andromeda Galaxy 1923 2.5 Mly This was the first galaxy determined to not be part of the Milky Way.[citation needed]
  • Mly represents millions of light-years, a measure of distance.
  • Distances are measured from Earth, with Earth being at zero.

Most distant galaxies

[edit]
See also: List of the most distant astronomical objects
Most Remote Galaxies by Type
Title Galaxy Date Redshift[b] Notes
Most remote galaxy of any type, confirmed (spectroscopic redshift) MoM-z14 2025 z=14.44 As of its announcement in May 2025.[77]
Most remote quasar UHZ1 2023 z=10.3
Further information: List of quasars

As of its announcement in 2023.[78][79][80]

Most distant Lyman-break galaxy MoM-z14 2025 z=14.44 [77]
Timeline of Most Remote Galaxy Record-holders[c]
Galaxy Date Distance
(z=Redshift)[b] 		Notes
MoM-z14 2025– z=14.44 [77][81]
JADES-GS-z14-0 2024–2025 z=14.32 [82][77]
JADES-GS-z13-0 2022–2024 z=13.20 [82]
GN-z11 2016–2022 z=11.09 Announced March 2016.[83][77]
EGSY8p7
(EGSY-2008532660) 		2015–2016 z=8.68 This galaxy's redshift was determined by examining its Lyman-alpha emissions, which were released in August 2015.[84][85]
EGS-zs8-1 2015–2015 z=7.730 This was the most distant galaxy as of May 2015.[86][87]
Z8 GND 5296 2013–2015 z=7.51 [88]
SXDF-NB1006-2 2012–2013 z=7.215 [89]
GN-108036 2012–2012 z=7.213 [90]
BDF-3299 2012–2013 z=7.109 [91]
IOK-1 2006–2010 z=6.96 This was the most remote object known at the time of discovery. In 2009, gamma ray burst GRB 090423 was discovered at z=8.2, taking the title of most distant object. The next galaxy to hold the title also succeeded GRB 090423, that being UDFy-38135539.[92][93][94]
SDF J132522.3+273520 2005–2006 z=6.597 This was the remotest object known at time of discovery.[94][95]
SDF J132418.3+271455 2003–2005 z=6.578 This was the remotest object known at time of discovery.[95][96][97][98]
HCM-6A 2002–2003 z=6.56 This was the remotest object known at time of discovery. The galaxy is lensed by galaxy cluster Abell 370. This was the first galaxy, as opposed to quasar, found to exceed redshift 6. It exceeded the redshift of quasar SDSSp J103027.10+052455.0 of z=6.28[96][97][99][100][101][102]
SSA22−HCM1 1999–2002 z=5.74 This was the remotest object known at time of discovery. In 2000, the quasar SDSSp J104433.04-012502.2 was discovered at z=5.82, becoming the most remote object in the universe known. This was followed by another quasar, SDSSp J103027.10+052455.0 in 2001, the first object exceeding redshift 6, at z=6.28[103][104]
HDF 4-473.0 1998–1999 z=5.60 This was the remotest object known at the time of discovery.[104]
RD1 (0140+326 RD1) 1998 z=5.34 This was the remotest object known at time of discovery. This was the first object found beyond redshift 5.[104][105][106][107][108]
CL 1358+62 G1 & CL 1358+62 G2 1997–1998 z=4.92 These were the remotest objects known at the time of discovery. The pair of galaxies were found lensed by galaxy cluster CL1358+62 (z=0.33). This was the first time since 1964 that something other than a quasar held the record for being the most distant object in the universe. It exceeded the mark set by quasar PC 1247-3406 at z=4.897[104][106][107][109][110][111]

From 1964 to 1997, the title of most distant object in the universe were held by a succession of quasars.[111] That list is available at list of quasars.

8C 1435+63 1994–1997 z=4.25 This is a radio galaxy. At the time of its discovery, quasar PC 1247-3406 at z=4.73, discovered in 1991 was the most remote object known. This was the last radio galaxy to hold the title of most distant galaxy. This was the first galaxy, as opposed to quasar, that was found beyond redshift 4.[104][112][113][114]
4C 41.17 1990–1994 z=3.792 This is a radio galaxy. At the time of its discovery, quasar PC 1158+4635, discovered in 1989, was the most remote object known, at z=4.73 In 1991, quasar PC 1247-3406, became the most remote object known, at z=4.897[104][113][114][115][116]
1 Jy 0902+343 (GB6 B0902+3419, B2 0902+34) 1988–1990 z=3.395 This is a radio galaxy. At the time of discovery, quasar Q0051-279 at z=4.43, discovered in 1987, was the most remote object known. In 1989, quasar PC 1158+4635 was discovered at z=4.73, making it the most remote object known. This was the first galaxy discovered above redshift 3. It was also the first galaxy found above redshift 2.[104][116][117][118][119]
3C 256 1984–1988 z=1.819 This is a radio galaxy. At the time, the most remote object was quasar PKS 2000-330, at z=3.78, found in 1982.[104][120]
3C 241 1984 z=1.617 This is a radio galaxy. At the time, the most remote object was quasar PKS 2000-330, at z=3.78, found in 1982.[121][122]
3C 324 1983–1984 z=1.206 This is a radio galaxy. At the time, the most remote object was quasar PKS 2000-330, at z=3.78, found in 1982.[104][121][123]
3C 65 1982–1983 z=1.176 This is a radio galaxy. At the time, the most remote object was quasar OQ172, at z=3.53, found in 1974. In 1982, quasar PKS 2000-330 at z=3.78 became the most remote object.
3C 368 1982 z=1.132 This is a radio galaxy. At the time, the most remote object was quasar OQ172, at z=3.53, found in 1974.[104]
3C 252 1981–1982 z=1.105 This is a radio galaxy. At the time, the most remote object was quasar OQ172, at z=3.53, found in 1974.
3C 6.1 1979 – z=0.840 This is a radio galaxy. At the time, the most remote object was quasar OQ172, at z=3.53, found in 1974.[104][124]
3C 318 1976 – z=0.752 This is a radio galaxy. At the time, the most remote object was quasar OQ172, at z=3.53, found in 1974.[104]
3C 411 1975 – z=0.469 This is a radio galaxy. At the time, the most remote object was quasar OQ172, at z=3.53, found in 1974.[104]

From 1964 to 1997, the title of most distant object in the universe were held by a succession of quasars.[111] That list is available at list of quasars.

3C 295 1960– z=0.461 This is a radio galaxy. This was the remotest object known at time of discovery of its redshift. This was the last non-quasar to hold the title of most distant object known until 1997. In 1964, quasar 3C 147 became the most distant object in the universe known.[104][111][125][126][127]
LEDA 25177 (MCG+01-23-008) 1951–1960 z=0.2
(V=61000 km/s) 		This galaxy lies in the Hydra Supercluster. It is located at B1950.0 08h 55m 4s +03° 21′ and is the BCG of the fainter Hydra Cluster Cl 0855+0321 (ACO 732).[104][127][128][129][130][131][132][133]
LEDA 51975 (MCG+05-34-069) 1936– z=0.13
(V=39000 km/s) 		The brightest cluster galaxy of the Bootes cluster (ACO 1930), an elliptical galaxy at B1950.0 14h 30m 6s +31° 46′ apparent magnitude 17.8, was found by Milton L. Humason in 1936 to have a 40,000 km/s recessional redshift velocity.[131][134][135]
LEDA 20221 (MCG+06-16-021) 1932 – z=0.075
(V=23000 km/s) 		This is the BCG of the Gemini Cluster (ACO 568) and was located at B1950.0 07h 05m 0s +35° 04′[134][136]
BCG of WMH Christie's Leo Cluster 1931–1932 z=
(V=19700 km/s) 		[136][137][138][139]
BCG of Baede's Ursa Major Cluster 1930–1931 z=
(V=11700 km/s) 		[139][140]
NGC 4860 1929–1930 z=0.026
(V=7800 km/s) 		[141][142]
NGC 7619 1929 z=0.012
(V=3779 km/s) 		Using redshift measurements, NGC 7619 was the highest at the time of measurement. At the time of announcement, it was not yet accepted as a general guide to distance; however, later in the year, Edwin Hubble described redshift in relation to distance, leading to a seachange, and having this being accepted as an inferred distance.[141][143][144]
NGC 584 (Dreyer nebula 584) 1921–1929 z=0.006
(V=1800 km/s) 		At the time, nebula had yet to be accepted as independent galaxies. However, in 1923, galaxies were generally recognized as external to the Milky Way.[131][141][143][145][146][147][148]
M104 (NGC 4594) 1913–1921 z=0.004
(V=1180 km/s) 		This was the second galaxy whose redshift was determined; the first being Andromeda—which is approaching us and thus cannot have its redshift used to infer distance. Both were measured by Vesto Melvin Slipher. At this time, nebula had yet to be accepted as independent galaxies. NGC 4594 was originally measured as 1000 km/s, then refined to 1100, and then to 1180 in 1916.[141][145][148]
M81 antiquity –
20th century[d] 		11.8 Mly z=-0.10) This is the lower bound, as it is remotest galaxy observable with the naked eye. It is 12 million light-years away. Redshift cannot be used to infer distance, because it is moving toward us faster than cosmological expansion.
Messier 101 1930– Using the pre-1950s Cepheid measurements, M101 was one of the most distant so measured.[citation needed]
Triangulum Galaxy 1924–1930 In 1924, Edwin Hubble announced the distance to M33 Triangulum.[citation needed]
Andromeda Galaxy 1923–1924 In 1923, Edwin Hubble measured the distance to Andromeda, and settled the question of whether or not there were galaxies, or if everything was in the Milky Way.
Small Magellanic Cloud 1913–1923 This was the first intergalactic distance measured. In 1913, Ejnar Hertzsprung measures the distance to SMC using Cepheid variables.

Timeline notes

[edit]
  • MACS0647-JD, discovered in 2012, with z=10.7, does not appear on this list because it has not been confirmed with a spectroscopic redshift.[149]
  • UDFy-38135539, discovered in 2009, with z=8.6, does not appear on this list because its claimed redshift is disputed.[150] Follow-up observations have failed to replicate the cited redshift measurement.[citation needed]
  • A1689-zD1, discovered in 2008, with z=7.6, does not appear on this list because it has not been confirmed with a spectroscopic redshift.
  • Abell 68 c1 and Abell 2219 c1, discovered in 2007, with z=9, do not appear on this list because they have not been confirmed.[151]
  • IOK4 and IOK5, discovered in 2007, with z=7, do not appear on this list because they have not been confirmed with a spectroscopic redshift.
  • Abell 1835 IR1916, discovered in 2004, with z=10.0, does not appear on this list because its claimed redshift is disputed. Some follow-up observations have failed to find the object at all.[citation needed]
  • STIS 123627+621755, discovered in 1999, with z=6.68, does not appear on this list because its redshift was based on an erroneous interpretation of an oxygen emission line as a hydrogen emission line.[152][153][154]
  • BR1202-0725 LAE, discovered in 1998 at z=5.64 does not appear on the list because it was not definitively pinned. BR1202-0725 (QSO 1202-07) refers to a quasar that the Lyman alpha emitting galaxy is near. The quasar itself lies at z=4.6947[105][108]
  • BR2237-0607 LA1 and BR2237-0607 LA2 were found at z=4.55 while investigating around the quasar BR2237-0607 in 1996. Neither of these appear on the list because they were not definitively pinned down at the time. The quasar itself lies at z=4.558[155][156]
  • Two absorption dropouts in the spectrum of quasar BR 1202-07 (QSO 1202-0725, BRI 1202-0725, BRI1202-07) were found, one in early 1996, another later in 1996. Neither of these appear on the list because they were not definitively pinned down at the time. The early one was at z=4.38, the later one at z=4.687, the quasar itself lies at z=4.695[104][157][158][159][160]
  • In 1986, a gravitationally lensed galaxy forming a blue arc was found lensed by galaxy cluster CL 2224-02 (C12224 in some references). However, its redshift was only determined in 1991, at z=2.237, by which time, it would no longer be the most distant galaxy known.[161][162]
  • An absorption drop was discovered in 1985 in the light spectrum of quasar PKS 1614+051 at z=3.21 This does not appear on the list because it was not definitively fixed down. At the time, it was claimed to be the first non-QSO galaxy found beyond redshift 3. The quasar itself is at z=3.197[104][163]
  • In 1975, 3C 123 was incorrectly determined to lie at z=0.637 (actually z=0.218).[164][165]
  • From 1964 to 1997, the title of most distant object in the universe was held by a succession of quasars.[111] That list is available at list of quasars.
  • In 1958, clusters Cl 0024+1654 and Cl 1447+2619 were estimated to have redshifts of z=0.29 and z=0.35, respectively. However, no galaxy was spectroscopically determined.[127]

Galaxies by brightness and power

[edit]
Title Galaxy Data Notes
Intrinsically brightest galaxy Baby Boom Galaxy Starburst galaxy located 12 billion light-years away[citation needed]
Brightest galaxy to the naked eye Large Magellanic Cloud Apparent magnitude 0.6 This galaxy has high surface brightness combined with high apparent brightness.[citation needed]
Intrinsically faintest galaxy Ursa Major III Absolute magnitude +2.2 This does not include dark galaxies.[citation needed]
Lowest surface brightness galaxy Andromeda IX
Most luminous galaxy WISE J224607.57−052635.0 As of 21 May 2015, WISE-J224607.57-052635.0-20150521 is the most luminous galaxy discovered and releases 10,000 times more energy than the Milky Way galaxy, although smaller. Nearly 100 percent of the light escaping from this dusty galaxy is Infrared radiation.[166][167] (Image)
Brightest distant galaxy (z > 6) Cosmos Redshift 7 Galaxy Cosmos Redshift 7 is reported to be the brightest of distant galaxies (z > 6) and to contain some of the earliest first stars (first generation; Population III) that produced the chemical elements needed for the later formation of planets and life as we know it.[11][168]

Galaxies by mass and density

[edit]
Title Galaxy Data Notes
Least massive galaxy Segue 2 ~550,000 MSun This is not considered a star cluster, as it is held together by the gravitational effects of dark matter rather than just the mutual attraction of the constituent stars, gas and black holes.[169][170]
Most massive galaxy ESO 146-5 27×1012 MSun Central galaxy in Abell 3827, 1.4 Gly distant.[171]
Most dense galaxy M85-HCC1 This is an ultra-compact dwarf galaxy[172]
Least dense galaxy
Most massive spiral galaxy ISOHDFS 27 1.04×1012 MSun The preceding most massive spiral was UGC 12591[173]
Least massive galaxy with globular cluster(s) Andromeda I [174]

Galaxies by size

[edit]
See also: List of largest galaxies
Title Galaxy Constellation Diameter Estimation method Notes
Smallest known galaxy Ursa Major III Ursa Major 3 parsecs (9.8 light-years)[175] Half-light radius A Milky Way satellite dwarf galaxy.[175]
Largest known galaxy ESO 383-76 Centaurus 540.89 kiloparsecs (1,764,000 light-years)[176][e] 90% total B-light Central galaxy of Abell 3571[177]
Largest spiral galaxy NGC 6872 Pavo 220 kiloparsecs (718,000 light-years) D25.5 isophote Interacting galaxy, stripped by IC 4970.[citation needed]
Largest irregular galaxy UGC 6697 Leo 62.82 kiloparsecs (205,000 light-years) D25 isophote Disrupted spiral-like galaxy, possible jellyfish galaxy.[citation needed]
Largest lenticular galaxy ESO 248-6 Eridanus 530.62 kiloparsecs (1,731,000 light-years) 90% total B-light Central galaxy of Abell 3112.[citation needed]
Largest starburst galaxy Abell 2125 BCG Ursa Minor 219.28 kiloparsecs (715,000 light-years) 2MASS K-band total mag
Largest radio galaxy TXS 0033+252 Andromeda 7,985 kiloparsecs (26,044,000 light-years)[178]

Interacting galaxies

[edit]
Main article: Interacting galaxy
Galaxies in tidal interaction
Galaxies Data Notes
The Magellanic Clouds are being tidally disrupted by the Milky Way Galaxy, resulting in the Magellanic Stream drawing a tidal tail away from the LMC and SMC, and the Magellanic Bridge drawing material from the clouds to the Milky Way galaxy.[citation needed]
The smaller galaxy NGC 5195 is tidally interacting with the larger Whirlpool Galaxy, creating its grand design spiral galaxy architecture.[citation needed]
These three galaxies interact with each other and draw out tidal tails, which are dense enough to form star clusters. The bridge of gas between these galaxies is known as Arp's Loop.[179]
NGC 6872 is a barred spiral galaxy with a grand design spiral nucleus, and distinct well-formed outer barred-spiral architecture, caused by tidal interaction with satellite galaxy IC 4970.[citation needed]
Tadpole Galaxy The Tadpole Galaxy tidally interacted with another galaxy in a close encounter, and remains slightly disrupted, with a long tidal tail.[citation needed]
Galaxies in non-merger significant collision
Galaxies Data Notes
Arp 299 (NGC 3690 & IC 694) These two galaxies have recently collided and are now both barred irregular galaxies.[citation needed]
Galaxies disrupted post significant non-merger collisions
Galaxies Data Notes
Mayall's Object This is a pair of galaxies, one which punched through the other, resulting in a ring galaxy.[citation needed]

Galaxy mergers

[edit]
Galaxies undergoing near-equal merger
Galaxies Data Notes
Antennae Galaxies (Ringtail Galaxy, NGC 4038 & NGC 4039, Arp 244) 2 galaxies Two spiral galaxies currently starting a collision, tidally interacting, and in the process of merger.[citation needed]
Eyes Galaxies (NGC 4435 & NGC 4438, Arp 120) 2 galaxies Two galaxies which have interacted or still interacting via an off-center collision, both had interacted with M86 in the past.[citation needed]
Butterfly Galaxies (Siamese Twins Galaxies, NGC 4567 & NGC 4568) 2 galaxies Two spiral galaxies in the process of starting to merge.[citation needed]
Mice Galaxies (NGC 4676, NGC 4676A & NGC 4676B, IC 819 & IC 820, Arp 242) 2 galaxies Two spiral galaxies currently tidally interacting and in the process of merger.[citation needed]
NGC 520 2 galaxies Two spiral galaxies undergoing collision, in the process of merger.[citation needed]
NGC 2207 and IC 2163 (NGC 2207 & IC 2163) 2 galaxies These are two spiral galaxies starting to collide, in the process of merger.[citation needed]
NGC 5090 and NGC 5091 (NGC 5090 & NGC 5091) 2 galaxies These two galaxies are in the process of colliding and merging.[citation needed]
NGC 7318 (Arp 319, NGC 7318A & NGC 7318B) 2 galaxies These are two starting to collide[citation needed]
Four galaxies in CL0958+4702 4 galaxies These four near-equals at the core of galaxy cluster CL 0958+4702 are in the process of merging.[180]
Galaxy protocluster LBG-2377 z=3.03 This was announced as the most distant galaxy merger ever discovered. It is expected that this proto-cluster of galaxies will merge to form a brightest cluster galaxy, and become the core of a larger galaxy cluster.[181][182]
Galaxy protocluster SPT2349-56 z=4.3 (14 galaxies) This protocluster is located at 12.4 billion light years from the Earth. Each of these galaxies are forming stars at 1000 times that of the Milky Way, nicknamed the Dusty Red Core.[183]
Recently merged galaxies of near-equals
Galaxy Data Notes
Starfish Galaxy (NGC 6240, IC 4625) This recently coalesced galaxy still has two prominent nuclei.[citation needed]
Galaxies undergoing disintegration by cannibalization
Disintegrating Galaxy Consuming Galaxy Notes
Canis Major Dwarf Galaxy Milky Way Galaxy The Monoceros Ring is thought to be the tidal tail of the disrupted CMa dg.[citation needed]
Virgo Stellar Stream Milky Way Galaxy This is thought to be a completely disrupted dwarf galaxy.[citation needed]
Sagittarius Dwarf Elliptical Galaxy Milky Way Galaxy M54 is thought to be the core of this dwarf galaxy.[citation needed]
Objects considered destroyed galaxies
Defunct Galaxy Destroyer Notes
Omega Centauri Milky Way Galaxy This is now categorized a globular cluster of the Milky Way. However, it is considered the core of a dwarf galaxy that the Milky Way cannibalized.[184]
Mayall II Andromeda Galaxy This is now categorized a globular cluster of Andromeda. However, it is considered the core of a dwarf galaxy that Andromeda cannibalized.[citation needed]
Gaia Sausage Milky Way Galaxy It is now considered a remnant of a dwarf galaxy that collided with the Milky Way about 8-11 billion years ago. It is the last major merger of the Milky Way in its lifetime.[citation needed]

Galaxies with some other notable feature

[edit]
Galaxy name Distance Constellation Property Notes
SDSS J081421.68+522410 Lynx Giant radio lobes Also termed Alcyoneus. Its radio lobes are some of the largest known structure made by a single galaxy.[185]
M87 Virgo [clarification needed] This is the central galaxy of the Virgo Cluster, the central cluster of the Local Supercluster[186] It contains the first black hole ever imaged, in April 2019, by the Event Horizon Telescope.[citation needed]
M102 Draco (Ursa Major) [clarification needed] This galaxy cannot be definitively identified, with the most likely candidate being NGC 5866, and a good chance of it being a misidentification of M101. Other candidates have also been suggested.
NGC 2770 Lynx "Supernova Factory" NGC 2770 is referred to as the "Supernova Factory" due to three recent supernovae occurring within it.
Arp 122 [clarification needed] Arp 122 is a collision of NGC 6040 and PGC 56942 or NGC 6039.
NGC 3314 (NGC 3314a and NGC 3314b) Hydra exact visual alignment This is a pair of spiral galaxies, one superimposed on another, at two separate and distinct ranges, and unrelated to each other. It is a rare chance visual alignment.
ESO 137-001 Triangulum Australe "tail" feature Lying in the galaxy cluster Abell 3627, this galaxy is being stripped of its gas by the pressure of the intracluster medium (ICM), due to its high speed traversal through the cluster, and is leaving a high density tail with large amounts of star formation. The tail features the largest amount of star formation outside of a galaxy seen so far. The galaxy has the appearance of a comet, with the head being the galaxy, and a tail of gas and stars.[187][188][189][190]
Comet Galaxy Sculptor interacting with a galaxy cluster Lying in galaxy cluster Abell 2667, this spiral galaxy is being tidally stripped of stars and gas through its high speed traversal through the cluster, having the appearance of a comet.
4C +37.11 230 Mpc Perseus Least separation between binary central black holes, at 24 ly (7.4 pc) OJ 287 has an inferred pair with a 12-year orbital period, and thus would be much closer than 4C 37.11's pair.
SDSS J150636.30+540220.9
15h 06m 36.30s+54° 02′ 20.9″
("SDSS J1506+54") 		z = 0.608 Boötes Most efficient star production Most extreme example in the list of moderate-redshift galaxies with the highest density starbursts yet observed found in the Wide-field Infrared Survey Explorer data (Diamond-Stanic et al. 2012).[191]
Cosmos Redshift 7 z = 6.604 Sextans Brightest distant galaxy (z > 6, 12.9 billion light-years) Galaxy Cosmos Redshift 7 is reported to be the brightest of distant galaxies (z > 6) and to contain some of the earliest first stars (first generation; Population III) that produced the chemical elements needed for the later formation of planets and life as we know it.[11][168]
RUBIES-UDS-QG-z7 z = 7.29 Cetus Earliest known massive quiescent galaxy This galaxy is reported to be the most distant and therefore earliest (700 million years after the Big Bang) massive galaxy where star formation stopped, contrary to expectations based on current models of galaxy formation.[192]
AMORE6 z = 5.725 Sculptor Most pristine galaxy This galaxy is reported to be very metal poor, with the oxygen abundance of 12+log(O/H) < 5.8 (2 sigma), or <0.12% of Solar abundance, measured via JWST spectroscopy. This metallicity measurement is the lowest in the literature, making it the most pristine galaxy to date.[193]
Galaxies (left/top, right/bottom): NGC 7541, NGC 3021, NGC 5643, NGC 3254, NGC 3147, NGC 105, NGC 2608, NGC 3583, NGC 3147, MRK 1337, NGC 5861, NGC 2525, NGC 1015, UGC 9391, NGC 691, NGC 7678, NGC 2442, NGC 5468, NGC 5917, NGC 4639, NGC 3972, The Antennae Galaxies, NGC 5584, M106, NGC 7250, NGC 3370, NGC 5728, NGC 4424, NGC 1559, NGC 3982, NGC 1448, NGC 4680, M101, NGC 1365, NGC 7329, NGC 3447

See also

[edit]

Lists of galaxies

[edit]
Main article: Lists of galaxies

Notes

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

List of galaxies

View on Grokipedia
from Grokipedia
A list of galaxies is a systematic compilation of astronomical observations documenting galaxies—vast, gravitationally bound systems of stars, stellar remnants, interstellar gas, dust, and dark matter that form the fundamental building blocks of the universe.[1] These lists, often organized into catalogs, provide essential data on positions, morphologies, sizes, distances, and other properties, aiding research into cosmic structure, evolution, and large-scale distribution. Ranging from historical compilations to contemporary databases, they capture a tiny fraction of the estimated 2 trillion galaxies in the observable universe.[2] The earliest notable lists emerged in the 18th century with the Messier Catalogue, compiled by Charles Messier to distinguish deep-sky objects from comets, which includes approximately 40 galaxies among its 110 entries visible from the Northern Hemisphere.[3] This was expanded in the 19th century by the New General Catalogue (NGC), which documents over 7,800 deep-sky objects, more than half of which are galaxies. In the 20th century, specialized galaxy catalogs proliferated, such as the Uppsala General Catalogue of Galaxies (UGC), containing 12,921 northern galaxies brighter than a limiting diameter of 1 arcminute.[4] Similarly, the Morphological Catalogue of Galaxies (MCG) provides detailed classifications for about 34,000 galaxies examined on blue-sky survey plates.[5] Modern lists leverage multi-wavelength observations from space telescopes like Hubble and James Webb, integrated into comprehensive resources such as the NASA/IPAC Extragalactic Database (NED), which as of October 2025 encompasses data on approximately 1.1 billion extragalactic objects, including redshifts for distance measurements.[6] These databases facilitate cross-identifications across surveys and support studies of phenomena like active galactic nuclei, galaxy clusters, and the cosmic microwave background. Notable subsets include lists of the nearest galaxies, such as those in the Local Group (over 50 members, dominated by the Milky Way and Andromeda), and the brightest or most peculiar galaxies, which highlight diverse morphologies from spirals to ellipticals.

Observable and named galaxies

Naked-eye galaxies

Galaxies visible to the unaided human eye are rare due to their great distances and low surface brightness, but under optimal conditions—such as Bortle scale 1-2 dark skies with minimal light pollution and low atmospheric extinction—a select few external galaxies can be discerned as faint, fuzzy patches distinct from stars.[7] These observations require keen eyesight, often aided by averted vision, and are best from locations far from urban areas; northern observers can spot targets in autumn evenings, while southern hemisphere viewers have access to additional objects year-round. Visibility is limited to objects with apparent magnitudes brighter than about 6.5, and their extended sizes (often spanning arcminutes to degrees) contribute to their detectability despite low contrast against the night sky.[8] Historical records of these galaxies date back over a millennium, reflecting their prominence in ancient skies. The Andromeda Galaxy (M31) was first documented in 964 CE by Persian astronomer Abd al-Rahman al-Sufi in his Book of Fixed Stars, where it appeared as a "nebulous smear" in the constellation of Andromeda; earlier unconfirmed sightings may trace to Persian records around 905 CE.[8] Chinese astronomers also noted it as early as the 10th century, describing it as a guest star or hazy object. The Magellanic Clouds, visible only from southern latitudes, were known to indigenous peoples long before European contact, appearing in petroglyphs and oral traditions of Australian Aboriginal and South American cultures as celestial campsites or emu footprints; they were first recorded by Europeans during Ferdinand Magellan's 1520-1521 circumnavigation. The Triangulum Galaxy (M33) was cataloged later, in 1764 by Charles Messier, though it may have been glimpsed earlier under pristine pre-industrial skies.[9] These galaxies hold cultural significance across societies. In Greek mythology, the Andromeda constellation—within which M31 resides—tells of Princess Andromeda chained to a rock, later rescued by Perseus, with the galaxy itself sometimes interpreted as her silhouette or a divine veil in folklore. The Large Magellanic Cloud featured in Polynesian navigation lore as a southern guidepost, while the Small Magellanic Cloud symbolized ancestral spirits in some Indigenous Australian Dreamtime stories. The following table summarizes key naked-eye galaxies, focusing on those reliably reported under dark conditions (apparent magnitudes <6.5 for consistent visibility, with borderline cases noted). Distances are referenced briefly for context, as these are among the closest external galaxies.
Galaxy NameCatalogApparent MagnitudeConstellationApparent SizeVisibility Notes
Large Magellanic Cloud-0.1Dorado/Mensa11° × 9°Easily visible as a bright patch from southern hemisphere (declination -70°); largest apparent size among external galaxies.[10]
Small Magellanic CloudNGC 2922.7Tucana5° × 3°Prominent fuzzy cloud from latitudes south of 15° N; irregular shape aids identification.[11]
Andromeda GalaxyM31/NGC 2243.4Andromeda3° × 1°Brightest external galaxy; visible worldwide north of 40° S, appears elongated like a cigar in autumn skies.[8]
Triangulum GalaxyM33/NGC 5985.7Triangulum1.2° × 0.7°Faint and diffuse; requires dark northern skies (best >40° N) and averted vision, occasionally spotted as a hazy spot near β Trianguli.[9]
Centaurus ANGC 51286.8Centaurus26' × 15'Borderline naked-eye object under exceptional southern dark skies; dusty lane gives it a distinct "dark rift" appearance to keen observers.[12]
Additional borderline candidates, such as Bode's Galaxy (M81, mag 6.9 in Ursa Major, ~27' × 14') and the Sculptor Galaxy (NGC 253, mag 7.0 in Sculptor, ~27' × 7'), have been reported by experienced observers in pristine conditions but are not reliably naked-eye for most people.[13] These objects underscore the galaxies' role in early astronomy, serving as fixed references for timekeeping and mythology before telescopes revealed their true nature.

Named galaxies

Named galaxies are those assigned descriptive, mythological, or honorific titles based on their appearance, location, or historical significance, often originating from early astronomical observations in the 18th and 19th centuries. These names provide cultural and visual context beyond systematic catalog designations like Messier or NGC numbers. Many were coined by astronomers such as Charles Messier, who cataloged over 100 deep-sky objects including several galaxies in the late 1700s, and later observers who noted distinctive features through telescopes. The etymologies frequently draw from everyday objects, ancient myths, or the scientists who first identified them, reflecting the era's blend of scientific discovery and imaginative description. The following table presents a selection of notable named galaxies in alphabetical order, including their primary catalog equivalents, brief etymologies, and first naming contexts. This list highlights representative examples rather than an exhaustive inventory.
NameCatalog EquivalentEtymology and Origin
Andromeda GalaxyM31, NGC 224Named after the constellation Andromeda, derived from Greek mythology where Andromeda was a princess chained to a rock as a sacrifice; the galaxy's location in this constellation led to the name, first noted as a nebula by ancient astronomers and cataloged by Messier in 1764.[14]
Antennae GalaxiesNGC 4038/4039Descriptive name for the pair's overlapping tails resembling insect antennae, coined after their discovery by William Herschel in 1785 and detailed in 20th-century imaging.[15]
Black Eye GalaxyM64, NGC 4826So named for the prominent dark dust lane obscuring its bright nucleus, evoking a "black eye"; discovered independently by Edward Pigott in 1779 and Johann Elert Bode shortly after, with the nickname popularized in the 19th century.[16]
Bode's GalaxyM81, NGC 3031Honors German astronomer Johann Elert Bode, who discovered it on December 31, 1774, while observing a comet; the name reflects his contributions to 18th-century catalogs.[17]
Cartwheel GalaxyESO 350-40Descriptive of its ring-like structure resembling a cartwheel, resulting from a galactic collision; discovered by Fritz Zwicky in 1941 and named in subsequent studies of its unusual morphology.[18]
Centaurus ANGC 5128Combines the constellation Centaurus with "A" as the first identified radio source in that region; discovered optically by James Dunlop in 1826, but the radio name emerged in the 1940s-1950s with early radio astronomy surveys.[19]
Sombrero GalaxyM104, NGC 4594Evokes the shape of a Mexican sombrero hat due to its bright central bulge and surrounding dust ring; first cataloged by Messier in 1781, with the nickname arising from 19th-century visual observations.[20]
Triangulum GalaxyM33, NGC 598Named for its position in the Triangulum constellation, which represents a triangle in Latin and was known to ancient Greeks; discovered by Giovanni Battista Hodierna before 1654 and added to Messier's catalog in 1764.[21]
Whirlpool GalaxyM51, NGC 5194Descriptive of its prominent spiral arms resembling a whirlpool; discovered by Messier on October 13, 1773, and further detailed by Lord Rosse in 1845, who coined an early version of the name based on his telescope observations.[22]
These names often persist in popular and scientific literature due to their evocative quality, aiding public engagement with astronomy. For instance, Messier's work laid the foundation for many such designations by highlighting visually striking objects, though descriptive names like "Whirlpool" and "Sombrero" emerged later as telescopes improved. Lesser-known examples, such as Ambartsumian's Knot (NGC 3561), honor Soviet astronomer Viktor Ambartsumian for his 1950s studies of active galactic nuclei.[15]

Historical and prototypical galaxies

Observational firsts

The earliest significant observational milestone in extragalactic astronomy occurred in 1845, when William Parsons, the 3rd Earl of Rosse, used his newly constructed 72-inch reflecting telescope—known as the Leviathan of Parsonstown—at Birr Castle, Ireland, to resolve the spiral structure of the Andromeda Nebula (M31). This instrument, the largest telescope in the world at the time with a 1.8-meter aperture, allowed Rosse to discern intricate spiral arms within the previously nebulous appearance of M31, marking the first visual confirmation of spiral morphology in what was later recognized as a galaxy beyond the Milky Way.[23] In 1885, the first supernova observed in an extragalactic system, designated S Andromedae or SN 1885A, erupted in the Andromeda Galaxy and was discovered on August 20 by Ernst Hartwig using a 6-inch refractor at Dorpat Observatory in Estonia. This event, which reached an apparent magnitude of about 6 and remained visible for roughly six months, provided early evidence of violent stellar processes outside our galaxy, though its extragalactic nature was not confirmed until decades later.[24][25] The definitive recognition of galaxies beyond the Milky Way came in the 1920s through Edwin Hubble's work at Mount Wilson Observatory. Using the 100-inch Hooker telescope, Hubble identified Cepheid variable stars in the Andromeda Nebula in 1923–1924, calculating its distance at approximately 900,000 light-years (later revised to 2.5 million), thereby establishing M31 as the first confirmed extragalactic system. Shortly after, in 1926, Hubble applied the same method to the Triangulum Galaxy (M33), identifying it as the second distinct galaxy outside our own at a distance of about 880,000 light-years.[26][27] Later milestones shifted to non-optical wavelengths, with Cygnus A becoming the first detected radio galaxy in 1939 through observations by Grote Reber using his pioneering 9.5-meter parabolic dish antenna in Wheaton, Illinois, which mapped strong radio emissions from this source in the constellation Cygnus. Optical identification in 1951 linked it to a distant elliptical galaxy harboring a supermassive black hole, advancing the study of active galactic nuclei. In 1963, Maarten Schmidt at Palomar Observatory identified the first quasar, 3C 273, by interpreting its optical spectrum as highly redshifted emission lines from a compact, luminous active galaxy core at a distance of about 2.4 billion light-years, using the 200-inch Hale telescope.[28][29]

Prototype galaxies

Prototype galaxies are those that exemplify the standard morphological types in the Hubble classification system, serving as archetypes for understanding galaxy structures. Edwin Hubble introduced this system in 1926, organizing galaxies into a sequence resembling a tuning fork diagram, with ellipticals at one end, lenticulars in the middle, and spirals branching into normal and barred variants.[30] This framework emphasized visual appearance based on early photographic observations, using representative examples to illustrate types from smooth, featureless ellipticals to loosely wound spirals.[31] In the elliptical branch, M87 (NGC 4486) exemplifies the E0 type, appearing nearly spherical with a smooth, featureless envelope and a prominent central nucleus, lacking any disk or spiral structure.[31] Highly flattened ellipticals, up to E7, show an elongated form when viewed edge-on, with a dominant bulge and minimal disk features, often transitional to lenticulars. For spirals, NGC 4594 (the Sombrero Galaxy, M104) is the classic Sa prototype, characterized by a large central bulge, tightly wound spiral arms, and a prominent dust lane encircling the bulge like a hat brim.[31] The Sb type is embodied by M51 (the Whirlpool Galaxy), featuring a moderate bulge, well-defined two-armed spirals, and tidal distortions from interaction with its companion NGC 5195, highlighting grand-design arm structure.[31] M33 (the Triangulum Galaxy) serves as the Sc archetype, with a small bulge, loose and patchy arms rich in star-forming regions, and low central concentration.[31] Barred spirals, denoted by SB, extend the sequence; NGC 1300 is a standard SBbc prototype, displaying a strong central bar that transitions smoothly into winding spiral arms, without inner rings, illustrating intermediate openness in arm structure.[31] Gérard de Vaucouleurs refined Hubble's system in 1959, expanding it into a three-dimensional classification incorporating stages, families (normal vs. barred), and varieties (rings, lenses), while adding lenticular (S0) and irregular extensions.[32] NGC 3115 prototypes the S0 lenticular type, showing an elongated, cigar-like form when viewed edge-on, with a prominent disk and bulge but no spiral arms, and a smooth stellar distribution.[31] For irregulars, the Magellanic types—represented by the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC)—exemplify asymmetric, patchy structures; the LMC shows a barred form with a single dominant arm and active star formation, while the SMC lacks a bar and exhibits disorganized clumps.[31] Modern classifications build on these foundations, incorporating dwarf galaxies like the Sculptor Dwarf as a dE (dwarf elliptical) prototype, featuring low luminosity, a smooth spheroidal shape, and possible nucleation, reflecting early evolutionary stages in low-mass systems.[31] These prototypes remain central to taxonomic studies, aiding in the interpretation of galaxy evolution and structural physics.

Galaxies by distance

Closest galaxies

The closest galaxies to the Milky Way are its satellite galaxies and other members of the Local Group, a gravitationally bound aggregation of more than 50 galaxies spanning a diameter of approximately 10 million light-years. These nearby systems provide critical insights into galactic interactions, dark matter distribution, and the assembly history of our cosmic neighborhood. The Milky Way dominates the Local Group alongside the Andromeda Galaxy (M31), with numerous dwarf galaxies orbiting or associating with these giants. Distances to these galaxies are primarily measured using stellar standard candles, including Cepheid variables for brighter systems like the Magellanic Clouds, RR Lyrae stars in globular clusters, and the tip of the red giant branch (TRGB) method for resolving individual stars in fainter dwarfs.[33][34][35] Among the nearest satellites, the Canis Major Dwarf Galaxy holds the distinction of being the closest known, situated about 25,000 light-years from the Sun and roughly 42,000 light-years from the Milky Way's center, though its status as a distinct galaxy remains debated due to its overlap with galactic disk stars. The Sagittarius Dwarf Spheroidal Galaxy follows at approximately 50,000 light-years, undergoing tidal disruption as it orbits the Milky Way, contributing to stellar streams in the halo. Further out, the Large Magellanic Cloud (LMC) lies at 163,000 light-years, and the Small Magellanic Cloud (SMC) at 200,000 light-years; both are irregular dwarfs visible from the Southern Hemisphere and actively interacting with the Milky Way. The Fornax Dwarf Spheroidal, at 460,000 light-years, exemplifies a more stable satellite with multiple globular clusters. Other prominent close satellites include the Sculptor Dwarf (260,000 light-years), the Ursa Minor Dwarf (228,000 light-years), and the Draco Dwarf (260,000 light-years), all classified as dwarf spheroidals with low surface brightness.[36][33]
Galaxy NameApproximate Distance (light-years)Type and Notes
Canis Major Dwarf42,000Dwarf irregular; closest, heavily obscured by galactic disk.
Sagittarius Dwarf50,000Dwarf spheroidal; tidally disrupting, source of stellar stream.
Large Magellanic Cloud163,000Irregular dwarf; brightest satellite, site of supernova 1987A.
Small Magellanic Cloud200,000Irregular dwarf; companion to LMC, gas-rich.
Draco Dwarf260,000Dwarf spheroidal; ancient stellar population.
Ursa Minor Dwarf228,000Dwarf spheroidal; metal-poor, dark matter dominated.
Sculptor Dwarf260,000Dwarf spheroidal; intermediate-age stars.
Sextans Dwarf280,000Dwarf spheroidal; low metallicity.
Carina Dwarf330,000Dwarf spheroidal; variable star formation history.
Fornax Dwarf460,000Dwarf spheroidal; multiple globular clusters, highest metallicity among dwarfs.
These distances are galactocentric estimates derived from TRGB and RR Lyrae measurements, with uncertainties typically under 10%.[33] The Local Group encompasses over 50 confirmed members, including about 60 satellite galaxies orbiting the Milky Way alone, many of which are ultra-faint dwarfs with luminosities below that of a single globular cluster. Orbital dynamics reveal dynamic interactions; for instance, the Magellanic Clouds are on their first infall trajectory around the Milky Way, having entered the halo within the last 3 billion years, and their gravitational influence has warped the outer Milky Way disk and generated the prominent Magellanic Stream of gas and stars trailing behind them. This interaction perturbs the Milky Way's rotation curve and halo structure, as evidenced by reflex motion in stellar streams. Beyond the Milky Way's immediate satellites, the Andromeda Galaxy at 2.5 million light-years serves as the closest major spiral, with its own retinue of dwarfs, foreshadowing a future merger with the Milky Way in about 4.5 billion years.[33][37][38][39] Recent observations from the European Space Agency's Gaia mission, particularly through data releases up to DR3 and preliminary DR4 insights by 2025, have revolutionized the census by identifying and confirming ultra-faint dwarf satellites via precise proper motions and photometry. These discoveries, such as Aquarius III and new candidates in the Carina and Phoenix regions, have added over a dozen previously unknown systems within 300,000 light-years, highlighting the incompleteness of earlier surveys and probing the Milky Way's extended dark matter halo. Such faint galaxies, often fainter than 10^5 solar luminosities, are key to understanding hierarchical galaxy formation.[40]

Most distant galaxies

The most distant galaxies observed to date provide critical insights into the early universe, formed mere hundreds of millions of years after the Big Bang. Their distances are quantified by redshift (z), a measure of how much light has stretched due to the universe's expansion, with higher z corresponding to greater distances and earlier epochs. Spectroscopic confirmation, often using the Lyman-alpha dropout technique to identify the redshifted Lyman break and emission lines, distinguishes these from photometric candidates. Light-travel time for these objects exceeds 13 billion years, meaning we see them as they were during the cosmic dawn, when the first stars and galaxies began ionizing the neutral hydrogen fog of the reionization epoch.[41][42] Prior to the James Webb Space Telescope (JWST), the record holders were identified using the Hubble Space Telescope, with confirmations limited to z ≈ 8–11 due to sensitivity constraints at near-infrared wavelengths. A seminal example is UDFy-3813557, spectroscopically confirmed at z = 8.55 in 2010 via the Very Large Telescope, representing light from approximately 13.1 billion years ago and marking the first secure detection beyond z = 7. Another landmark was GN-z11, confirmed at z = 11.09 in 2016 with Hubble's Wide Field Camera 3, observed as it existed 13.4 billion years ago and notable for its unexpectedly high ultraviolet luminosity, suggesting rapid early star formation.[43] These pre-JWST discoveries established the framework for high-redshift galaxy searches but revealed only the tip of the iceberg, as deeper infrared observations were needed to probe beyond z = 11. The advent of JWST in 2022 revolutionized this field, enabling spectroscopic confirmations at z > 12 through its NIRSpec instrument, which captures faint, redshifted emission lines. The JWST Advanced Deep Extragalactic Survey (JADES) has been pivotal, uncovering a population of surprisingly massive and luminous galaxies in the first 300–400 million years after the Big Bang, far exceeding predictions from pre-JWST models of galaxy formation. For instance, discoveries from 2022–2023 included JADES-GS-z13-0 at z = 13.20, confirmed via NIRSpec spectroscopy showing a clear Lyman break. By 2024, JADES confirmed JADES-GS-z14-0 at z = 14.32, observed 290 million years post-Big Bang, with a UV magnitude of -20.8 indicating a stellar mass of about 5 × 10^8 solar masses—challenging hierarchical formation scenarios by implying accelerated growth.[42] In May 2025, the Mirage or Miracle (MoM) survey pushed the frontier further with MoM-z14 at z = 14.44, confirmed spectroscopically in the COSMOS field, visible just 280 million years after the Big Bang and boasting high equivalent widths in UV lines suggestive of a rising star-formation history.[41] These JWST-era findings, spanning 2022–2025, have revealed an unexpectedly high number density of bright galaxies at z ≈ 14–15, over 100 times greater than forecasted, prompting revisions to models of dark matter halo assembly and feedback processes. They coincide with the reionization epoch (z ≈ 6–15), where ultraviolet photons from these galaxies likely contributed to clearing the intergalactic medium, as evidenced by detections of ionized gas around JADES-GS-z14-0. However, tensions arise: the presence of metals and dust in these early systems implies faster chemical enrichment than standard simulations allow, potentially requiring adjustments to initial mass functions or bursty star formation. Ongoing surveys like JADES continue to refine these insights, with over a dozen confirmed z > 12 galaxies by late 2025.[41][42] The following table summarizes select confirmed most distant galaxies, focusing on spectroscopic records from major surveys (ordered by decreasing z):
Galaxy NameRedshift (z)Light-Travel Time (Gyr ago)Discovery YearSurvey/InstrumentKey Notes
MoM-z1414.4413.52 (0.28 Gyr after Big Bang)2025MoM/JWST-NIRSpecLuminous (M_UV = -20.2); high UV line strengths indicate young, metal-poor stars.[41]
JADES-GS-z14-014.3213.51 (0.29 Gyr after Big Bang)2024JADES/JWST-NIRSpecMass ≈ 5×10^8 M_⊙; evidence of oxygen emission, suggesting early enrichment.[42]
JADES-GS-z13-013.2013.47 (0.33 Gyr after Big Bang)2023JADES/JWST-NIRSpecFirst z > 13 confirmation; compact size implies merger-driven growth.
GN-z1111.0913.40 (0.40 Gyr after Big Bang)2016Hubble/WFC3Pre-JWST record; UV luminosity 3× L* at z~6–8, hinting at Population III stars.[43]
UDFy-38135578.5513.10 (0.70 Gyr after Big Bang)2010VLT/X-ShooterFirst z > 8 spectroscopic detection; faint Lyα emission during reionization.

Galaxies by physical properties

Galaxies by brightness and luminosity

Galaxies are ranked by brightness in two primary ways: apparent brightness, which measures how bright they appear from Earth and depends on both intrinsic luminosity and distance, and absolute luminosity, which quantifies their total energy output independent of distance. Apparent brightness is typically expressed in magnitudes, where lower values indicate brighter objects; the brightest galaxies visible to the naked eye include the Large Magellanic Cloud with an integrated apparent magnitude of +0.6 in V-band and the Andromeda Galaxy (M31) at +3.4, both discernible under dark skies from appropriate hemispheres.[44] Absolute luminosity, often measured in solar luminosities (L⊙), captures the total bolometric output across all wavelengths, requiring integration of flux from ultraviolet to radio to account for dust obscuration and emission mechanisms. Bolometric luminosity is derived by applying corrections to observed fluxes in specific bands, such as combining optical, infrared, and radio data to estimate total energy release from stars, active galactic nuclei (AGN), or other processes.[45] Typical galaxies, classified as L* in luminosity functions, emit around 2 × 10¹⁰ L⊙, comparable to the Milky Way's integrated stellar output.[46] Among the most luminous galaxies, supergiant ellipticals like IC 1101 stand out with a bolometric luminosity of approximately 10¹² L⊙, driven by trillions of stars in its vast halo. Ultra-luminous infrared galaxies (ULIRGs), defined as systems exceeding 10¹² L⊙ in infrared luminosity (integrated from 8–1000 μm), often result from mergers fueling intense starbursts or AGN activity obscured by dust.[47] Examples include Arp 220, a merging starburst galaxy with an infrared luminosity over 10¹² L⊙, where dust-reprocessed star formation dominates the output.[48] In the radio regime, Alcyoneus exhibits exceptional extended emission with a total low-frequency radio luminosity density of 80 × 10²⁴ W Hz⁻¹ at 144 MHz, equivalent to a projected radio power far exceeding typical galaxies when integrated over its lobes.[49] Categories of highly luminous galaxies highlight diverse emission mechanisms. Optically bright examples like M87, with an absolute V-band magnitude of -22 (corresponding to ~5 × 10¹⁰ L⊙), shine prominently in visible light due to its dense stellar population and prominent jet. Infrared-luminous starbursts, such as Arp 220, re-emit absorbed ultraviolet light as thermal dust emission, making them appear faint optically but radiant at longer wavelengths. AGN host galaxies, like Centaurus A, feature low-luminosity nuclei (log L_{2-10 keV} ≈ 41.6 erg s⁻¹) powered by supermassive black holes, with jets contributing to radio and X-ray brightness.[50][51] Recent observations have uncovered even more extreme ULIRGs using facilities like ALMA, revealing dusty, high-redshift systems. For instance, WISE J224607.57–052635.0, a hot dust-obscured galaxy at z ≈ 4.6, achieves a bolometric luminosity of ~3.5 × 10¹⁴ L⊙, likely driven by a rapidly accreting quasar amid merger-induced turbulence, as traced by submillimeter molecular outflows.[52]
CategoryExample GalaxyKey Luminosity MetricPrimary Emission MechanismSource
Optically BrightM87Absolute V-mag: -22 (~5 × 10¹⁰ L⊙)Stellar light + jet[50]
Infrared Starburst (ULIRG)Arp 220>10¹² L⊙ (8–1000 μm)Dust-reprocessed star formation[48]
AGN HostCentaurus Alog L_{2-10 keV} ≈ 41.6 erg s⁻¹Black hole accretion + jets[51]
Extreme ULIRGWISE J224607.57–052635.0~3.5 × 10¹⁴ L⊙ (bolometric)Quasar + merger outflows[52]
Radio-LuminousAlcyoneus80 × 10²⁴ W Hz⁻¹ (144 MHz)Relativistic lobes/jets[49]

Galaxies by mass and density

Galaxies are categorized by their total mass, which encompasses stellar, gaseous, and dark matter components, as well as by their density profiles, which describe how mass is distributed within their structures. Total mass estimates for galaxies range from ultra-faint dwarfs with as little as 10510^5 solar masses (M⊙M_\odot) to massive ellipticals exceeding 1012M⊙10^{12} M_\odot in stellar content alone, with dark matter halos extending these totals significantly higher. Density profiles often follow models like the Navarro-Frenk-White (NFW) distribution for dark matter-dominated systems, revealing cuspy or cored structures that inform formation histories through mergers and environmental interactions. These properties are crucial for understanding galaxy evolution within the cosmic web, where massive galaxies anchor dense clusters and low-mass ones populate voids. The most massive known galaxies are typically brightest cluster galaxies (BCGs) in rich clusters, such as IC 1101, the central cD galaxy in Abell 2029, with an estimated stellar mass of approximately 1012M⊙10^{12} M_\odot and a total dynamical mass, including its extended halo, approaching 1014M⊙10^{14} M_\odot. Similarly, the BCG in Abell 2029 exhibits comparable mass scales, derived from its dominant role in the cluster's potential, with stellar masses around 1.1×1012M⊙1.1 \times 10^{12} M_\odot. These giants form through repeated mergers in high-density environments, accumulating vast envelopes that contribute to their extreme masses. Galaxy masses are inferred using several techniques that probe gravitational effects. The virial theorem applies to dynamically relaxed systems, equating kinetic energy from stellar or gas velocities to gravitational potential energy to estimate total mass within clusters like Coma, where Fritz Zwicky first inferred dark matter's presence in 1933. Gravitational lensing, as observed in the Bullet Cluster, maps mass distributions by distorting background light, revealing separated baryonic and dark components with total cluster masses around 1014M⊙10^{14} M_\odot. Rotation curves of spiral galaxies trace flat velocity profiles out to large radii, indicating extended dark matter halos that dominate the total mass budget. Density profiles vary markedly with environment, with high-density regions hosting cD galaxies like those in rich clusters, where central surface brightness envelopes extend over large scales in dense intracluster media. These cD systems exhibit extended halos embedded in high-density cluster cores, with galaxy number densities peaking at 10310^3 galaxies per Mpc³ near the center. In contrast, low-density voids, such as the Eridanus Supervoid spanning over 1 billion light-years, contain galaxies in underdense regions with matter densities about 20% below the cosmic average, confirmed as significant underdensities at redshifts z<0.2z < 0.2. At the low-mass end, dwarf galaxies like Segue 2 represent the least massive systems, with a total mass within its half-light radius of approximately 4×105M⊙4 \times 10^5 M_\odot, yielding a high mass-to-light ratio of about 500 M⊙/L⊙M_\odot / L_\odot. This ultra-faint dwarf, a satellite of the Milky Way, exemplifies tidally stripped remnants where dark matter still dominates despite minimal stellar content. In typical spiral galaxies, dark matter constitutes the majority of the mass, comprising about 85% of the total, as seen in the Milky Way with an overall mass of roughly 1012M⊙10^{12} M_\odot within its virial radius of ~200 kpc. Recent surveys have highlighted underappreciated populations like ultra-diffuse galaxies (UDGs), discovered using the Dragonfly Telescope, which are dark matter-dominated even in their centers; for instance, Dragonfly 44 in the Coma Cluster has a dynamical mass of ~8 × 10^8 M⊙ within the effective radius (revised from earlier estimates as of 2019; van Dokkum et al. 2019), with stars accounting for less than 1% of the total.[53] These UDGs, observed in 2020s datasets including JWST, challenge models by showing varied dark matter fractions, from nearly baryon-free to cluster-like halos. As of 2023, JWST observations have refined UDG properties, confirming these revisions.

Galaxies by size

Galaxy size is typically measured using the isophotal diameter, defined as the extent where the surface brightness reaches a standard threshold of 25 magnitudes per square arcsecond in the B-band, which captures the optical footprint of the stellar component.[54] Complementary measurements from radio observations trace the extent of the neutral hydrogen (HI) disk, often revealing larger gaseous envelopes that extend beyond the stellar light, providing insights into the dark matter halo influence.[55] These metrics highlight morphological variations: elliptical galaxies often feature extended low-surface-brightness envelopes due to their diffuse stellar distributions, while spiral galaxies exhibit more compact bulges surrounded by structured disks.[56] Among the largest known galaxies, the supergiant elliptical IC 1101 holds a record with an isophotal diameter of approximately 500,000 light-years (debated extended envelope up to ~1 million light-years), making it vastly larger than the Milky Way's 100,000 light-year extent. In the spiral category, Malin 1 exemplifies supergiant low-surface-brightness spirals, with an optical diameter of about 650,000 light-years derived from deep imaging that reveals its faint, extended disk.[57] These giants illustrate how size correlates loosely with mass in the mass-size relation, where larger galaxies tend to enclose more stellar and dark matter, though environmental factors play a role.[58] At the opposite end, ultra-faint dwarf galaxies represent the smallest known systems, such as Boötes II, which spans roughly 500 light-years across based on its half-light radius measurements from resolved star counts.[59] These diminutive galaxies, with luminosities comparable to a globular cluster, probe the low-mass end of galaxy formation and are often satellites of larger hosts like the Milky Way. Ring galaxies, like Hoag's Object, offer unique size benchmarks with their annular structures; this example has a ring diameter of about 100,000 light-years, enclosing a central bulge and highlighting collisionless ring formation mechanisms.[60] Recent observations from the Euclid mission (2023–2025) have confirmed ultra-diffuse galaxies (UDGs) with exceptionally large extents, some reaching up to 200 kiloparsecs in diameter, expanding our understanding of these low-surface-brightness systems beyond previous surveys.[61] These findings underscore the diversity in galaxy sizes, from compact dwarfs to sprawling giants, shaped by hierarchical assembly in the cosmic web. As of 2023, JWST observations have further refined UDG size and mass properties.

Special and interacting galaxies

Interacting galaxies

Interacting galaxies refer to systems where two or more galaxies are currently exchanging gravitational influences, leading to dynamical distortions without yet completing a full merger. These interactions typically occur between gas-rich spirals and manifest as elongated tidal tails, connecting bridges of material, and warped disks, all driven by differential gravitational forces that strip stars, gas, and dust from the outer regions. Such phenomena are observable across a range of distances and provide key insights into galaxy evolution, as the tidal forces compress gas clouds and trigger enhanced star formation.[62] Prominent examples include the Antennae Galaxies (NGC 4038 and NGC 4039), a pair of colliding spirals approximately 68 million light-years away, where the interaction began 200–300 million years ago and has produced prominent tidal tails extending over 100,000 light-years. These tails consist of stripped material, including young stars and gas, with the southern tail showing a smooth velocity gradient from 1590 to 1784 km/s in HI observations. Similarly, the Mice Galaxies (NGC 4676), located about 300 million light-years distant, exhibit long, curved tidal tails resembling rodent whiskers, formed during a head-on collision that has tidally triggered bursts of star formation across both disks, enhancing the overall rate in localized regions. Another notable pair is Arp 302 (also known as VV 340 or UGC 9618), a gas-rich system in early interaction stages, where ultraviolet observations reveal bright emission from the face-on southern galaxy, indicating active star-forming regions disturbed by the edge-on companion.[63][64][65] The Arp Atlas of Peculiar Galaxies catalogs numerous such pairs, emphasizing morphological peculiarities from ongoing interactions; for instance, Arp 77 displays a clear bridge connecting the galaxies, Arp 81 shows distorted arms with tidal extensions, and Arp 87 features a prominent tidal tail linking the primary spiral to its companion. These structures arise from the relative orbital motions, where simulations indicate typical relative velocities of 100–300 km/s during pericenter passages, leading to orbital periods on the order of 200–500 million years for disk-dominated systems like the Antennae or Mice. In the Mice, N-body/hydrodynamical models reproduce the tail formation over multiple pericenter encounters spaced ~2.2 Gyr apart, with the current phase showing minimal nuclear starburst but elevated formation in the tails. For the Antennae, restricted three-body simulations match the observed kinematics with an initial relative velocity of ~150 km/s and an orbital timescale of ~250 million years since first encounter.[66][67][68] Recent James Webb Space Telescope (JWST) observations have extended these studies to the early universe, revealing interacting pairs at redshifts z > 6 (corresponding to less than 900 million years after the Big Bang), where major mergers with projected separations of 20–50 kpc show elevated star formation rates enhanced by 0.25–0.26 dex compared to isolated galaxies. These high-redshift pairs, often compact due to their small separations and high densities, contribute significantly to stellar mass growth, with merger rates stabilizing at ~6 Gyr⁻¹ beyond z = 6 and accounting for 71 ± 25% of mass accretion in massive galaxies (log₁₀(M*/M⊙) = 8.0–10.0). Examples include merger-induced clumps in systems at z = 6.81 and multi-galaxy interactions at z = 6.7, highlighting compact dynamical processes that fuel rapid evolution. As of 2025, JWST has also identified the "Cosmic Vine," a chain of 20 interacting galaxies spanning 13 million light-years at high redshift, offering new insights into filamentary structures in the early universe.[69][70]

Galaxies with unique features

Galaxies exhibiting unique features often display rare structural or dynamical anomalies that challenge standard models of galactic evolution. Active galaxies, powered by supermassive black holes at their cores, are prominent examples, with Centaurus A (NGC 5128) showcasing vast radio lobes extending over a million light-years, formed by relativistic jets from its active nucleus.[71] These lobes, visible in radio emissions, result from material ejected at near-light speeds, interacting with the intergalactic medium and creating diffuse structures observable across multiple wavelengths.[72] Similarly, the giant elliptical galaxy Messier 87 (M87) features a prominent relativistic jet, first imaged at event-horizon scales by the Event Horizon Telescope in 2019, revealing a bright ring of emission around its central black hole and a jet extending thousands of light-years.[73] This jet, powered by accretion onto a 6.5 billion solar mass black hole, ejects plasma at relativistic velocities, providing key insights into black hole feedback processes.[74] Peculiar galaxy types further illustrate structural uniqueness, such as ring galaxies formed through dynamical instabilities. The Cartwheel Galaxy, a prototypical example, developed its prominent outer ring through a head-on collision with a smaller companion approximately 200 million years ago, propagating a density wave that triggered intense star formation along the ring.[75] This collision-induced structure contrasts with typical spiral arms, creating an expanding ripple of young, blue stars and gas.[76] Polar-ring galaxies, like NGC 2685 (the Helix Galaxy), possess an orthogonal ring of gas, dust, and stars encircling a lenticular disk, likely accreted from a disrupted companion or tidal interaction, orbiting perpendicular to the main galactic plane.[77] This configuration, spanning about 100,000 light-years, offers a rare laboratory for studying angular momentum transfer in galactic mergers.[78] Extreme environments highlight galaxies isolated from typical cosmic structures, such as those in cosmic voids. NGC 6503, a dwarf spiral at the edge of the Local Void—a vast underdense region spanning tens of millions of light-years—exhibits low stellar density and minimal external influences, resulting in a pristine, unevolved disk with subdued star formation rates.[79] This isolation, about 17 million light-years from the Milky Way, preserves its morphological integrity amid the void's sparse matter distribution.[80] At high redshifts, James Webb Space Telescope (JWST) observations have revealed massive galaxies at z ≈ 10–14 that defy hierarchical formation models, appearing overly mature with significant stellar masses (up to 10^9 solar masses) and disk-like structures just 300–500 million years after the Big Bang.[42] The JADES survey, for instance, identified JADES-GS-z14-0 at z=14.32, a luminous galaxy with bright emission lines indicating rapid metal enrichment and star formation, challenging simulations of early universe galaxy assembly.[81] In 2025, JWST observations have uncovered potential direct collapse black holes in early interacting galaxies, such as the Infinity Galaxy formed by a head-on collision, further challenging models of supermassive black hole formation in the young universe.[82] Other notable galaxies emphasize aesthetic and structural rarities, including the Sombrero Galaxy (M104), whose nearly edge-on view reveals a striking dust lane encircling a bright bulge, composed of dense interstellar material absorbing light and outlining the spiral arms over 50,000 light-years.[83] This prominent equatorial dust ring, spanning 30 million light-years in the Virgo Cluster, highlights the role of dust in shaping galactic appearance and obscuring the nucleus. Hoag's Object (PGC 54559), a rare ring galaxy 600 million light-years away, presents a near-perfect circular ring of young blue stars surrounding an older yellow core, possibly formed by a slow bar instability or external perturbation, with the ring diameter exceeding 100,000 light-years.[84] Its symmetry and lack of spokes distinguish it as a prototype for non-collisional ring formation.[85] Merger remnants can yield ultra-compact dwarfs, dense stellar systems stripped of outer envelopes. M60-UCD1, the densest known galaxy with 140 million stars packed into a 300-light-year diameter, is believed to be the core remnant of a larger galaxy tidally disrupted by the massive elliptical M60, retaining a supermassive black hole of 21 million solar masses at its center.[86] This object, 54 million light-years away, exemplifies how mergers can compact nucleated galaxies into ultra-compact dwarfs with half-light radii under 100 parsecs, preserving high velocities and old stellar populations from the progenitor.[87]

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