A Hickson Compact Group (abbreviation: HCG) is a collection of
galaxies
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. ...
designated as published by Paul Hickson in 1982.
The most famous group on Hickson's list of 100 objects is HCG 92,
Stephan's Quintet
Stephan's Quintet is a visual grouping of five galaxies of which four form the first compact galaxy group ever discovered. The group, visible in the constellation Pegasus, was discovered by Édouard Stephan in 1877 at the Marseille Observatory.
...
.
Hickson Compact Groups
According to Hickson: “Most compact groups contain a high fraction of galaxies having morphological or kinematical peculiarities, nuclear radio and
infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from aroun ...
emission, and
starburst or
active galactic nuclei
An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much-higher-than-normal luminosity over at least some portion of the electromagnetic spectrum with characteristics indicating that the luminosity is not prod ...
(AGN) activity. They contain large quantities of diffuse gas and are dynamically dominated by
dark matter
Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not ab ...
. They most likely form as subsystems within looser associations and evolve by gravitational processes. Strong galaxy interactions result and merging is expected to lead to the ultimate demise of the group. Compact groups are surprisingly numerous, and may play a significant role in galaxy evolution.”
List
Gallery
Image:A fossil in the making.jpg, NGC 201 is a barred spiral galaxy similar to the Milky Way
The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked ey ...
, a member of HCG 7
Image:A members-only galaxy club.jpg, HCG 22 by Hubble Space Telescope
The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most ver ...
Hubble Space Telescope
The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most ver ...
Image:HCG 31 HST.jpg, HCG 31 by Hubble Space Telescope
The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most ver ...
Image:Hickson Compact Group 31.jpg, HCG 31
Image:Hickson44HunterWilson.jpg, The four members of HCG 44
Hickson 44 (HCG 44) is a group of galaxies in the constellation Leo. As Arp 316, a part of this group is also designated as group of galaxies in the Atlas of Peculiar Galaxies.
Members
References
44
Leo (constellation)
{{galaxy ...
by Hunter Wilson
See also
*
Abell catalogue
The Abell catalog of rich clusters of galaxies is an all-sky catalog of 4,073 rich galaxy clusters of nominal redshift ''z'' ≤ 0.2. This catalog supplements a revision of George O. Abell's original "Northern Survey" of 1958, wh ...
*
Catalogue of Galaxies and Clusters of Galaxies
References
Further reading
*
*
External links
*
Astronomy Picture of the Day
Astronomy Picture of the Day (APOD) is a website provided by NASA and Michigan Technological University (MTU). According to the website, "Each day a different image or photograph of our universe is featured, along with a brief explanation written ...
�
Galaxy Group Hickson 31– 22 February 2010
{{Use dmy dates, date=July 2019
Astronomical catalogues of galaxy clusters