The following table lists polar-ring galaxies:
|Image||Galaxy||Base galaxy type||Notes|
|NGC 2685 (UGC 4666, Arp 336, Helix Galaxy)||Lenticular (S0)|||
|NGC 4650A (ESO 322-IG69, AM 1241-402)||Lenticular (S0)|||
|ESO 415-G26 (AM 0226-320)||Lenticular (S0)|||
|UGC 5119 (LEDA 27383)||Elliptical|||
|UGC 7576||Lenticular (S0)|||
|UGC 9796 (II Zwicky 73)||Lenticular (S0)|||
Some galaxies feature a "polar ring" within the disk of the galaxy
The following is a list of notable galaxies.
There are about 51 galaxies in the Local Group (see list of nearest galaxies for a complete list), on the order of 100,000 in our Local Supercluster and an estimated number of about one to two trillion in all of the observable universe.
The discovery of the nature of galaxies as distinct from other nebulae (interstellar clouds) was made in the 1920s. 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.There is no universal naming convention for galaxies, as they are mostly catalogued before it is established whether the object is or isn't a galaxy. Mostly they are identified by their celestial coordinates together with the name of the observing project (HUDF, SDSS, 3C, CFHQS, NGC/IC, etc.)Lists of astronomical objects
This is a list of lists, grouped by type of astronomical object.Lists of galaxies
This is a list of lists of galaxies.NGC 660
NGC 660 is a peculiar and unique polar-ring galaxy located approximately 45 million light years from Earth in the Pisces constellation. It is the only such galaxy having, as its host, a "late-type lenticular galaxy". It was probably formed when two galaxies collided a billion years ago. However, it may have first started as a disk galaxy that captured matter from a passing galaxy. This material could have, over time, become "strung out" to form a rotating ring.
The ring is not actually polar, but rather has an inclination from the plane of the host disk of approximately 45 degrees. The extreme number of pinkish star-forming areas that occurs along the galaxy's ring could be the result of the gravitation interaction caused by this collision. The ring is 50,000 light-years across - much broader than the disk itself - and has a greater amount of gas and star formation than the host ring. This likely indicates a very violent formation. The polar ring contains objects numbering in the hundreds. Many of these are red and blue supergiant stars. The most recently created stars in the ring were just formed approximately 7 million years ago. This indicates that the formation of these stars has been a long process and is still occurring.
Data about the dark matter halo of NGC 660 can be extracted by observing the gravitational effects of the dark matter on the disk and ring's rotation. From the core of the disk, radio waves are being emitted. The source of these waves is an area only 21 light years across. This may indicate the presence of a super-cluster of stars located within an area of cloud of gas.
The region in the centre has a vast amount of star formation, so luminous that it is considered to be a starburst galaxy.Late in 2012, this polar-ring galaxy produced an enormous outburst having a magnitude of approximately ten times brighter than a supernova explosion. The cause is not certain, but this event may have resulted from a tremendous jet being emenating from galaxy's central black hole.NGC 660 is a member of the M74 Group.Polar-ring galaxy
A polar-ring galaxy is a type of galaxy in which an outer ring of gas and stars rotates over the poles of the galaxy. These polar rings are thought to form when two galaxies gravitationally interact with each other. One possibility is that a material is tidally stripped from a passing galaxy to produce the polar ring seen in the polar-ring galaxy. The other possibility is that a smaller galaxy collides orthogonally with the plane of rotation of the larger galaxy, with the smaller galaxy effectively forming the polar-ring structure.The best-known polar-ring galaxies are S0s (lenticular galaxies), but from the physical point of view they are part of a wider category of galaxies, including several ellipticals.
The first four S0 galaxies that were identified as polar-ring galaxies were NGC 2685, NGC 4650A, A 0136 -0801, and ESO 415 -G26. While these galaxies have been extensively studied, many other polar-ring galaxies have since been identified. Polar-ring S0 galaxies may be found around 0.5% of all nearby lenticular galaxies, and it is possible that 5% of lenticular galaxies may have had polar rings at some point during their lifetimes.The first polar-ring elliptical galaxies were identified in 1978. They were NGC 5128, NGC 5363, NGC 1947 and Cygnus A, while the polar-ring S0 galaxies NGC 2685 and NGC 4650A were at that time indicated as resulting from similar formation processes. Only some years later, when the first observations of the stellar and gas motion of polar-ring elliptical and S0 galaxies were possible with a better spectroscopic technology, the external origin of the gaseous rings was clarified. In addition to the best-known example, NGC 5128 (Cen A), a very regular polar ring elliptical, is NGC 5266