Robert's Quartet
Under the name of Roberts Quartet conceals a compact group of galaxies, which is approximately 160 million light-years away from Earth. The constellation is found near the center of the constellation Phoenix. It represents summarized a family of four very different galaxies, which are in a process of mutual influence. The cluster includes the galaxies NGC 87, NGC 88, NGC 89 and NGC 92, all of which were discovered by John Herschel on September 30, 1834.
Description
NGC 87 (top right ) is an irregular galaxy, similar to those located in the neighborhood of our Milky Way Magellanic Clouds. NGC 88 (middle ) is a barred spiral galaxy with a diffuse external enclosure which most likely made up of gas. NGC 89 ( bottom center ) is a barred spiral galaxy with two large spiral arms. The largest member of the system is NGC 92 ( top left), a spiral galaxy of morphological type Sa of unusual appearance. One of his arms, with a length of about 100,000 light-years, was shaped by interactions and contains a large amount of dust.
The Quartet is one of the best examples of a compact group of galaxies. Since such groups are summarized from four to eight galaxies in a relatively small area to find they make excellent study objects that for the study of galactic interactions and their effects, especially on the constellation of stars. The quartet has a total Apparent magnitude of nearly 13, the brightest member of the group case has a visual magnitude of 13.8. In heaven, the four galaxies are united within a radius of 1.6 arc minutes, which is equivalent to a distance of 75,000 light years.
Origin of the name
They were named by astronomers Halton Arp and Barry F. Madore, the directory A Catalogue of Southern Peculiar Galaxies and Associations presented together ( A catalog of unusual galaxies and associations in the southern hemisphere) in 1987. It was named after Robert Freedman, the calculated many of the updated positions of the galaxies in the catalog.