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 Édouard Jean-Marie Stephan (31 August 1837 – 31 December 1923) was a French astronomer. His surname is sometimes spelled Stéphan in some literature, but this is apparently erroneous. He was born in Sainte Pezenne (today one of the districts ...

in 1877 at the

Marseille Observatory Marseille Observatory (french: Observatoire de Marseille) is an astronomical observatory located in Marseille, France, with a history that goes back to the early 18th century. In its 1877 incarnation, it was the discovery site of a group of gal ...

. The group is the most studied of all the compact galaxy groups. The brightest member of the visual grouping (and the only non-member of the true group) is NGC 7320, which has extensive

H II region An H II region or HII region is a region of interstellar atomic hydrogen that is ionized. It is typically in a molecular cloud of partially ionized gas in which star formation has recently taken place, with a size ranging from one to hundreds ...

s, identified as red blobs, where active star formation is occurring. Four of the five galaxies in Stephan's Quintet form a physical association, a true

galaxy group A galaxy group or group of galaxies (GrG) is an aggregation of galaxies comprising about 50 or fewer gravitationally bound members, each at least as luminous as the Milky Way (about 1010 times the luminosity of the Sun); collections of galaxie ...

Hickson Compact Group A Hickson Compact Group (abbreviation: HCG) is a collection of galaxies 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. Hickson Compact Groups According to Hi ...

92, and will likely merge with each other. Radio observations in the early 1970s revealed a filament of emission between the galaxies in the group. This same region is also detected in the faint glow of ionized atoms seen in the visible part of the spectrum as a green arc. Space telescopes have provided new insight into the nature of the filament, which is now believed to be a shock-wave in the intergalactic gas, caused by one galaxy (NGC 7318B) falling into the center of the group at several millions of kilometres per hour. Stephan's Quintet was selected as one of the five cosmic objects observed by the James Webb Space Telescope as part of the release of its first official science images.

Emissions

X-rays

As NGC 7318B collides with gas in the group, a huge shock wave bigger than the Milky Way spreads throughout the medium between the galaxies, heating some of the gas to temperatures of millions of degrees where they emit X-rays detectable with the

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the US federal government responsible for the civil List of government space agencies, space program ...

Chandra X-ray Observatory The Chandra X-ray Observatory (CXO), previously known as the Advanced X-ray Astrophysics Facility (AXAF), is a Flagship-class space telescope launched aboard the during STS-93 by NASA on July 23, 1999. Chandra is sensitive to X-ray sources 1 ...

Molecular hydrogen emission

The

Spitzer Space Telescope, which detects infrared radiation, discovered a very powerful molecular hydrogen signal from the shock wave between the galaxies. This emission is one of the most turbulent formations of molecular hydrogen ever seen, and the strongest emission originates near the center of the green area in the visible light picture discussed earlier. This phenomenon was discovered by an international team led by scientists at the

California Institute of Technology The California Institute of Technology (branded as Caltech or CIT)The university itself only spells its short form as "Caltech"; the institution considers other spellings such a"Cal Tech" and "CalTech" incorrect. The institute is also occasional ...

and including scientists from Australia, Germany and China. The detection of molecular hydrogen from the collision was initially unexpected because the hydrogen molecule is very fragile and is easily destroyed in shock waves of the kind expected in Stephan's Quintet. However, one solution is that when a shock front moves through a cloudy medium like the center of the group, millions of smaller shocks are produced in a turbulent layer, and this can allow molecular hydrogen to survive. Stephans Quintet sdss-g Goran Nilsson & The Liverpool Telescope

Stephans Quintet sdss-g Goran Nilsson & The Liverpool Telescope

Redshift

NGC 7320 indicates a small redshift (790 km/s) while the other four exhibit large redshifts (near 6,600 km/s). Since galactic redshift is proportional to distance, NGC 7320 is only a foreground projection and is ~39 million light-years from

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

, making it a possible member of the NGC 7331 group, versus the 210–340 million light-years of the other four. NGC 7319 has a type 2 Seyfert nucleus. StephansQuintettIlustrated2

A sixth galaxy, NGC 7320C, probably belongs to the Hickson association: it has a redshift similar to the Hickson galaxies, and a tidal tail appears to connect it with NGC 7319. StephansQuintet3

Infrared

Using its Mid Infrared Instrument (MIRI), the James Webb Space Telescope shows details shrouded by dust in visible light including large shock waves and tidal tails in four of the five galaxies, and previously hidden areas of star formation. These new details will contribute to insights on galaxy evolution. STScI-01G7NDA42495H05DYFR9XPZSCA

Members

In popular culture

The angelic figures at the beginning of the 1946 holiday film ''

It's a Wonderful Life ''It's a Wonderful Life'' is a 1946 American Christmas fantasy drama film produced and directed by Frank Capra, based on the short story and booklet ''The Greatest Gift'', which Philip Van Doren Stern self-published in 1943 and is in turn loos ...

'' are based on images of Stephan's Quintet.

Gallery

File:NGC7317 CDK Large04.jpg, Stephan's Quintet acquired with 17" PlaneWave CDK scope by W4SM in Louisa, VA File:Stephan's Quintet taken by James Webb Space Telescope.jpg, alt=Image mosaic of Stephan's Quintet, Near-to-mid-infrared composite of

NIRCam NIRCam (Near-InfraRed Camera) is an instrument aboard the James Webb Space Telescope. It has two major tasks, as an imager from 0.6 to 5 micron wavelength, and as a wavefront sensor to keep the 18-section mirrors functioning as one. In other wor ...

and MIRI imagery from the James Webb Space Telescope.

References

External links

GALEX: Stephan's Quintet and NGC 7331

Star Clusters Born in the Wreckage of Cosmic Collisions

NightSkyInfo.com : Stephan's Quintet

What's Behind Stephan's Quintet?
Peter Edmonds, Chandra Blog, 21 July 2009 * Astronomy Picture of the Day on Stephan's Quintet

NASA’s James Webb Space Telescope reveals never-before-seen details of the galaxy group called “Stephan’s Quintet.”
* {{Portal bar, Astronomy, Stars, Spaceflight, Outer space, Solar System 92 Pegasus (constellation) Astronomical objects discovered in 1877