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This is a list of ring galaxies. A ring galaxy, as the name suggests, is a disc or spiral galaxy with its galactic disc structured or distorted into a ring or torus-like appearance. Hoag's Object, discovered by Art Hoag in 1950, is the prototypical example of a ring galaxy.
Ring galaxies are theorized to be formed through multiple possible situations:
1. Bar instability – a phenomenon where the rotational velocity of the bar in a barred spiral galaxy increases to the point of spiral spin-out. Under typical conditions, gravitational density waves would favor the creation of spiral arms. When bar instability occurs, these density waves are instead migrated out into a ring-structure by the pressure, force, and gravitational influence of the byronic and dark matter furiously orbiting about the bar. This migration forces the stars, gas and dust found within the former arms into a torus-like region, forming a ring, and often igniting star formation.
2. Galactic collisions- another observed way that ring galaxies can form is through the process of two or more galaxies colliding. The cartwheel galaxy, galaxy pair AM 2026-424, and Arp 147 are all examples of ring galaxies believed to be formed from this process. In pass-through galactic collisions, an often smaller galaxy will pass through the disc of an often larger spiral, causing an outward push of the arms, as if dropping a rock into a pond of still water. In side-swipe and head-on collisions, the appearance of a perfect ring are less likely, with chaotic and warped appearances dominating.
3. Intergalactic medium accretion- this method has been inferred through the existence of Hoag's object, along with UV observations of several other large and ultra-large super spiral galaxies and current formation theories of spiral galaxies. UV-light observations show several cases of faint, ring-like and spiral structures of hot young stars that have formed along the network of cooled inflowing gas, extending far from the visible luminous galactic disc. If conditions are favorable, a ring can form in the place of a spiral structure. Since some spiral galaxies are theorized to have formed from massive clouds of intergalactic gas collapsing and then rotationally forming into a disc structure, one could assume that a ring disc could form in place of a spiral disc if, as mentioned before, conditions are favorable. This holds true for protogalaxies, or galaxies just throughout to be forming, and old galaxies that has migrated into a section of space with a higher gas content than its previous locations.
| Name | Image | Catalogue number | Distance | Notes |
|---|---|---|---|---|
| Cartwheel Galaxy |  | ESO 350-40, PGC 2248 | 500 Mly | lenticular galaxy |
| NGC 6028 |  | NGC 6028, NGC 6046, PGC 56716 | 203 Mly | barred lenticular galaxy |
| NGC 1015 |  | |||
| Hoag's Object |  | PGC 54559, PRC D-51 | 600 Mly | |
| SDSS J151713.93+213516.8 |  | This galaxy can be seen behind Hoag's Object | ||
| AM 0644-741 |  | AM 0644-741 | 300 Mly | |
| NGC 4909 |  | PGC 44949, ESO 269-035, MCG -07-27-028 | ||
| NGC 1291 |  | NGC 1291, NGC 1269, [1] PGC 012209 | 33 Mly | |
| NGC 1512 |  | PGC 14391 | 38 Mly | Galaxy exhibits a double-ring structure |
| NGC 1433 |  | PGC 13586 | 49 Mly | barred spiral galaxy with ring |
| NGC 1533 |  | NGC 1533, PGC 14582 [2] | 62 ± 4 Mly [3] | lenticular galaxy with ring structure |
| NGC 2859 |  | UGC 5001, PGC 26649 | 82.8 Mly | lenticular galaxy with ring structure [4] |
| NGC 1350 |  | PGC 013059 | 87.4 Mly | spiral galaxy with ring structure |
| NGC 1386 |  | PGC 13333 | 53 Mly | spiral galaxy with ring structure |
| NGC 1387 |  | PGC 13344 | 53 Mly | lenticular galaxy with nuclear ring |
| NGC 4622 |  | PGC 42701 | 200 Mly | unbarred spiral galaxy with ring |
| NGC 4777 |  | NGC 4777, PGC 43852 | 180 Mly | |
| NGC 6861 |  | |||
| NGC 7217 |  | UGC 11914, PGC 68096 | 50 Mly | unbarred spiral galaxy with ring |
| ESO 509-098 |  | PGC 48609 | 350 Mly | |
| II Zw 28 [5] |  | Zw II 28, 2MASX J05014205+0334278 | 390 Mly | |
| Mayall's Object |  | Arp 148, VV 032, MCG+07-23-019, APG 148 | 450 Mly | collisional ring galaxy |
| NGC 4774 [6] |  | I Zw 045 | 413 Mly | collisional ring galaxy |
| VII Zw 466 [6] |  | VII Zw 466, UGC 07683 | 637 Mly | collisional ring galaxy |
| Arp-Madore 417-391 [7] |  | PGC 14881 | 670 Mly | collisional ring galaxy |
| UGC 4599 |  | 91 Mly | ||
| UGC 6614 |  | PGC 36122 | 322 Mly | giant low surface brightness galaxy |
| UGC 7069 |  | PGC 38254, MCG +07-25-017 | 708 Mly | Largest ring galaxy [8] |
| Arp 10 [6] |  | Arp 10, UGC 01775, 2MASX J02182639+0539139 [9] | 400 Mly | collisional ring galaxy |
| Arp 146 |  | PGC 509 | 1050 Mly | interacting pair |
| Arp 147 |  | IC 298 | 430 Mly | interacting pair |
| NGC 4650A |  | PGC 42951 | 126 Mly | polar ring galaxy |
| NGC 660 |  | polar ring galaxy | ||
| NGC 922 |  | ESO 478-28, ISG 10 | 150 Mly | collisional ring galaxy |
| ESO 198-13 |  | PGC 9463 | 237 Mly | three ring structures |
| LEDA 1000714 |  | PGC 1000714, 6dFGS gJ112316.4-084007, 2MASX J11231643-0840067 | 360 Mly | two nearly round rings, but with different characteristics |
| NGC 985 |  | VV 285, Mrk 1048, MCG -02-07-035, PGC 9817 | 567 Mly | collisional ring galaxy |
| NGC 1142 |  | NGC 1144, UGC 2389, Arp 118, VV 331a, Mrk 1504, CGCG 389-046, MCG +00-08-048, PGC 11012 | 375 Mly | Seyfert galaxy |
| NGC 3081 |  | IC 2529, ESO 499-G31, AM 0957-223, MCG -04-24-012, PGC 28876 | 83 Mly | barred lenticular galaxy |
| NGC 3821 |  | CGCG 127-32, MCG 4-28-30, PGC 36314, UGC 6663 | 271 Mly | low surface brightness galaxy |
| NGC 4513 |  | CGCG 315-42, MCG 11-15-59, PGC 41527, UGC 7683 | 110 Mly | lenticular galaxy |
| NGC 7020 |  | NGC 7021, ESO 107-13, PGC 66291 | 138 Mly | barred lenticular galaxy |
| NGC 7098 |  | ESO 48-5, IRAS 21393-7520, PGC 67266 | 95 Mly | double barred spiral galaxy |
| NGC 7552 |  | IC 5294, ESO 291- G 012, VV 440, PGC 70884 | 56 Mly | barred spiral galaxy |
| NGC 7742 |  | UGC 12760,[2] MCG +02-60-010,[2] UZC J234415.8+104601,[2] 2MASX J23441571+1046015 | 72 Mly | Unbarred spiral galaxy with ring, Seyfert galaxy |
| IC 2628 |  | PGC 34038, CGCG 067-030 | 601 Mly | |
| IC 5285 |  | PGC 70497, UGC 12365 | 286 Mly | |
| 2MASX J09015145+5212411 |  | LEDA 2409366 | 819 Mly | lenticular galaxy with ring structure |
| MCG +07-07-072 |  | PGC 12535 | 320 Mly | Barred spiral galaxy with a ring [10] |
| WISEA J033303.20-275041.5 |  | 1790 Mly | Discovered in the Hubble Legacy Field | |
| CN AC118 108 |  | 3757 Mly | ||
| LT 41 |  | 2MASX J00075757-0433255 | 1004 Mly | |
| CFRS 14.0685 |  | WISEA J141757.82+523050.1 | 1153 Mly | Discovered in Extended Groth Strip |
| CFRS 14.0117 |  | EGSIRAC J141819.73+523424.4 | 2613 Mly | Discovered in Extended Groth Strip |
| Z 229-15 |  | PGC 62756 | 390 Mly | Also a quasar and a Seyfert galaxy. |
| [BZR2017] J051631.16-542938.9 |  | |||
| CANDELS EGS F160W J141952.0+525115.2 |  | 9813 Mly | Discovered in Extended Groth Strip, its distance calculated with redshift is around 9813 Mly, very faint, very distant | |
| DES J024008.08-551047.5 | DES J0240 | Its rings have a distinct coloration then the main host galaxy [11] | ||
| 2MASX J07273754-0254540 |  | 2MASX J07273754-0254540, PSCz Q07251-0248, IRAS 07251-0248 | 1207 Mly | interacting pair |
| 2MASS J01074878+5406541 |  | 1446 Mly | Spiral ring galaxy | |
| WISEA J010752.28+540643.9 |  | on the right side of the piccture | ||
| SDSS J091450.23+085326.2 |  | 1825 Mly |
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. The word is derived from the Greek galaxias (γαλαξίας), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. Galaxies, averaging an estimated 100 million stars, range in size from dwarfs with less than a thousand stars, to the largest galaxies known – supergiants with one hundred trillion stars, each orbiting its galaxy's center of mass. Most of the mass in a typical galaxy is in the form of dark matter, with only a few percent of that mass visible in the form of stars and nebulae. Supermassive black holes are a common feature at the centres of galaxies.
Hoag's Object is an unusual ring galaxy in the constellation of Serpens Caput. It is named after Arthur Hoag, who discovered it in 1950 and identified it as either a planetary nebula or a peculiar galaxy. The galaxy has a D25 isophotal diameter of 45.41 kiloparsecs (148,000 light-years).
Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae and, as such, form part of the Hubble sequence. Most spiral galaxies consist of a flat, rotating disk containing stars, gas and dust, and a central concentration of stars known as the bulge. These are often surrounded by a much fainter halo of stars, many of which reside in globular clusters.
An irregular galaxy is a galaxy that does not have a distinct regular shape, unlike a spiral or an elliptical galaxy. Irregular galaxies do not fall into any of the regular classes of the Hubble sequence, and they are often chaotic in appearance, with neither a nuclear bulge nor any trace of spiral arm structure.
In astronomy, a galactic bulge is a tightly packed group of stars within a larger star formation. The term almost exclusively refers to the central group of stars found in most spiral galaxies. Bulges were historically thought to be elliptical galaxies that happened to have a disk of stars around them, but high-resolution images using the Hubble Space Telescope have revealed that many bulges lie at the heart of a spiral galaxy. It is now thought that there are at least two types of bulges: bulges that are like ellipticals and bulges that are like spiral galaxies.
A ring galaxy is a galaxy with a circle-like appearance. Hoag's Object, discovered by Arthur Hoag in 1950, is an example of a ring galaxy. The ring contains many massive, relatively young blue stars, which are extremely bright. The central region contains relatively little luminous matter. Some astronomers believe that ring galaxies are formed when a smaller galaxy passes through the center of a larger galaxy. Because most of a galaxy consists of empty space, this "collision" rarely results in any actual collisions between stars. However, the gravitational disruptions caused by such an event could cause a wave of star formation to move through the larger galaxy. Other astronomers think that rings are formed around some galaxies when external accretion takes place. Star formation would then take place in the accreted material because of the shocks and compressions of the accreted material.
The terms galactic corona and gaseous corona have been used in the first decade of the 21st century to describe a hot, ionised, gaseous component in the galactic halo of the Milky Way. A similar body of very hot and tenuous gas in the halo of any spiral galaxy may also be described by these terms.
A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed of stars. Bars are found in about two thirds of all spiral galaxies in the local universe, and generally affect both the motions of stars and interstellar gas within spiral galaxies and can affect spiral arms as well. The Milky Way Galaxy, where the Solar System is located, is classified as a barred spiral galaxy.
Messier 94 is a spiral galaxy in the mid-northern constellation Canes Venatici. It was discovered by Pierre Méchain in 1781, and catalogued by Charles Messier two days later. Although some references describe M94 as a barred spiral galaxy, the "bar" structure appears to be more oval-shaped. The galaxy has two ring structures.
NGC 1365, also known as the Fornax Propeller Galaxy or the Great Barred Spiral Galaxy, is a double-barred spiral galaxy about 56 million light-years away in the constellation Fornax. It was discovered on 2 September 1826 by Scottish astronomer James Dunlop.
Interacting galaxies are galaxies whose gravitational fields result in a disturbance of one another. An example of a minor interaction is a satellite galaxy disturbing the primary galaxy's spiral arms. An example of a major interaction is a galactic collision, which may lead to a galaxy merger.
NGC 1512 is a barred spiral galaxy approximately 38 million light-years away from Earth in the constellation Horologium. The galaxy displays a double ring structure, with a (nuclear) ring around the galactic nucleus and an (inner) further out in the main disk. The galaxy hosts an extended UV disc with at least 200 clusters with recent star formation activity. NGC 1512 is a member of the Dorado Group.
Arp 107 is a pair of interacting galaxies located about 450 million light-years away in the constellation Leo Minor. The galaxies are in the process of colliding and merging.
Galaxy mergers can occur when two galaxies collide. They are the most violent type of galaxy interaction. The gravitational interactions between galaxies and the friction between the gas and dust have major effects on the galaxies involved, but the exact effects of such mergers depend on a wide variety of parameters such as collision angles, speeds, and relative size/composition, and are currently an extremely active area of research. Galaxy mergers are important because the merger rate is a fundamental measurement of galaxy evolution and also provides astronomers with clues about how galaxies grew into their current forms over long stretches of time.
NGC 1808 is a barred spiral galaxy located in the southern constellation of Columba, about two degrees to the south and east of Gamma Caeli. It was discovered on 10 May 1826 by Scottish astronomer James Dunlop, who described it as a "faint nebula". The galaxy is a member of the NGC 1808 group, which is part of the larger Dorado Group.
NGC 3504 is a barred spiral galaxy in the constellation Leo Minor. It has a Hubble distance corresponding to 88 million light-years and was discovered by William Herschel in 1785.
UGC 2885 is a large barred spiral galaxy of type SA(rs)c in the constellation Perseus. It is 232 million light-years (71 Mpc) from Earth and measures 463,000 ly (142,000 pc) across, making it one of the largest known spiral galaxies. It is also a possible member of the Perseus–Pisces Supercluster.
NGC 1433 is a barred spiral galaxy with a double ring structure located in the constellation of Horologium. It was discovered by James Dunlop on 28 September 1826, and lies a distance of 46 million light-years from Earth.
NGC 7469 is an intermediate spiral galaxy in the constellation of Pegasus. NGC 7469 is located about 200 million light-years away from Earth, which means, given its apparent dimensions, that NGC 7469 is approximately 90,000 light-years across. It was discovered by William Herschel on November 12, 1784.
NGC 6951 is a barred spiral galaxy located in the constellation Cepheus. It is located at a distance of about 75 million light-years from Earth, which, given its apparent dimensions, means that NGC 6951 is about 100,000 light-years across. It was discovered by Jérôme Eugène Coggia in 1877 and independently by Lewis Swift in 1878.
