A polar annular galaxy is a type of galaxy in which an outer ring of gas and stars rotates about the galaxy's poles. These polar rings are believed to form when two galaxies gravitationally interact with each other. One possibility is that a material is tidally stripped from a galaxy that happens 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. They are galaxies in which a ring of gas and stars rotates about the poles of the galaxy. Its origin would be in the interaction between two galaxies. So, when approaching, the material of one of them (the less massive) enters a polar orbit around the other. Like annular galaxies, they are very rare and not many are known today. Although, thanks to the Sloan Digital Sky Survey, which collected information from many, many objects, just over a hundred polar annular galaxies are known. The polar structure, by the way, is not unique to these galaxies. For example, the elliptical dwarf galaxy Sagittarius, which is colliding with our galaxy, is in a polar orbit, warped like a long series of stars. In any case, they are just two examples of galaxies that go beyond what can be considered normal. So, like, of course irregular galaxies. But none come close to the strange appearance of the Hoag Object. In a sense, it looks like two galaxies in one. The exterior is typical of a spiral galaxy, with the intense blue color of recently formed stars. Something typical in the spiral arms of galaxies like Andromeda, the Milky Way and many others. The interior, however, shows the typical appearance of an elliptical galaxy. Perhaps in the future, with better technology, it will be possible to better understand its origin.
_____________
Source: James Binney, Michael Merrifield (1998). Princeton University Press, ed. Galactic Astronomy. Princeton, New Jersey
Comentarios
Publicar un comentario