Stephan's Quintet: A Galaxy Grouping in 2D and 3D.
Jun 24, 2019 18:47:27 GMT -5
Post by Radrook Admin on Jun 24, 2019 18:47:27 GMT -5
Stephan's Quintet
Galaxy cluster in the Pegasus.
Stephan's Quintet is in the constellation Pegasus. It is a visual grouping of five galaxies of which four are the first compact galaxy group ever discovered. The group is about 280 million light years from Earth.
The group was discovered by Édouard Stephan in 1877 at Marseille Observatory. It is the most studied of all the compact galaxy groups. The brightest member of the visual grouping is NGC 7320. This has extensive H II regions, seen here as red blobs, where active star formation is occurring.
These galaxies are of interest because of their violent collisions. Four of the five galaxies in Stephan's Quintet form a physical association, Hickson Compact Group 92. They are involved in a cosmic dance that will probably end with the galaxies merging.
Radio observations in the early 1970s showed a mysterious emission from the inter-galactic space between the galaxies in the group. This same region also showed faint glow of ionized atomic hydrogen. You can see this in the visible part of the spectrum as the magnificent green-blue arc in the picture to the right. Two space telescopes have recently shown something about the nature of the strange filament. It is now believed to be a giant intergalactic shock-wave (similar to a sonic boom but traveling in intergalactic gas rather than air). This is caused by one galaxy (NGC 7318B) falling into the center of the group at several million miles per hour.
The light blue galaxy NGC 7320 is a foreground galaxy, only 40 million light years from Earth.
About this video
Duration: 1 minute, 48 seconds
In 1877, Edouard Stephan discovered a tight visual grouping of five galaxies located in the constellation Pegasus. The galaxies of Stephan's Quintet are both overlapping and interacting, and have become the most famous among the compact groups of galaxies.
Astronomers have long known that four of the galaxies (all of which are yellowish-white in this video) form a physical group in space, while the fifth (bluish) is a foreground galaxy.
In addition, a sixth galaxy (yellowish-white and on the far left) is likely to be part of the physical grouping. Hence, this 2D quintet that is a 3D quartet may actually be a 2D sextet that is a 3D quintet.
This visualization makes apparent the spatial distribution of these galaxies. The video starts with a view that matches our 2D perspective. As the sequence travels in 3D, the foreground blue spiral, NGC 7320, quickly passes by the camera.
The possible sixth galaxy member on the left, NGC 7320C, is seen at roughly the same distance as the remaining four galaxies.
The camera turns to pass between two strongly interacting galaxies, NGC 7319 (left) and NGC 7318B (right), with each galaxy's spiral structure distorted by the gravitational interaction. In contrast, NGC 7318B overlaps in 2D with the more distant elliptical NGC 7318A, but does not have a strong interaction.
The other elliptical, NGC 7317, is also seen as more distant than the strongly interacting pair. In 3D, the four or five galaxies in this group are gathered together by their mutual gravity, and may collide and merge together in the future.
hubblesite.org/video/1207/science