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NGC 7318
NGC 7318
	NGC 7318 imaged by the Hubble Space Telescope. 8-micrometre infrared light = red, H-alpha = green, visible red light = blue. NGC 7318b is the upper galaxy, NGC 7318a is the lower galaxy.
Observation data (J2000 epoch)
Constellation	Pegasus
Right ascension	22h 35m 56.7s / 22h 35m 58.4s
Declination	+33° 57′ 56″ / +33° 57′ 57″
Redshift	6630 ± 23 / 5774 ± 24 km/s
Distance	85 Mpc
Apparent magnitude (V)	14.4 / 13.9
Characteristics
Type	E2 pec / SB(s)bc pec
Apparent size (V)	0.9′ × 0.9′ / 1.9′ × 1.2′
Notable features	Colliding galaxies
Other designations
	NGC 7318A / 7318B; UGC 12099 / 12100; Arp 319; PGC 69260 / 69263; HCG 92D / 92B;
	References:

The location of NGC 7318 (circled in blue)

NGC 7318 (also known as UGC 12099/UGC 12100 or HCG 92d/b) is a pair of colliding galaxies about 280 million light-years from Earth.^[1] They appear in the Constellation Pegasus and are members of Stephan's Quintet.^[3] They were discovered on 27 September 1873 by French astronomer Édouard Stephan.^[4]

The Spitzer Space Telescope revealed the presence of a large intergalactic shock wave, shown by an arc produced by NGC 7318b colliding with the group at ≥ 900 km/sec.^[5]

As NGC 7318b collides with NGC 7318a, atoms of hydrogen in the cluster's gas are heated by the shock wave, producing the green glow. The molecular hydrogen visible in the collision is one of the most turbulent forms known. This phenomenon was discovered by an international team of scientists of the Max Planck Institute for Nuclear Physics (MPIK) in Heidelberg. This collision can help provide a view into what happened in the early universe, around ten billion years ago.

References

^ ^a ^b Duc, Pierre-Alain; Cuillandre, Jean-Charles; Renaud, Florent (March 2018). "Revisiting Stephan's Quintet with deep optical images". Monthly Notices of the Royal Astronomical Society: Letters. 475 (1): L40 – L44. arXiv:1712.07145. Bibcode:2018MNRAS.475L..40D. doi:10.1093/mnrasl/sly004.
^ "NASA/IPAC Extragalactic Database". Results for NGC 7318a / 7318b. Retrieved 2006-10-23.
^ Arp, Halton (July 1973). "Stephan's Quintet of Interacting Galaxies". Astrophysical Journal. 183: 411–440. Bibcode:1973ApJ...183..411A. doi:10.1086/152236. Retrieved 9 February 2021.
^ Seligman, Courtney. "New General Catalogue Objects: NGC 7318". Celestial Atlas. Retrieved 28 August 2024.
^ Xu, C. K.; Appleton, P. N.; Dopita, M.; Gao, Y.; Lu, N. Y.; Popescu, C.; Reach, W. T.; Sulentic, J.; Tuffs, R.; Yun, M. (March 2008). "Spitzer Observations of Stephan's Quintet -- IGM Dust and Gas in a Multi-galaxy Collision". The Second Annual Spitzer Science Center Conference: Infrared Diagnostics of Galaxy Evolution. ASP Conference Series. 381: 88. Bibcode:2008ASPC..381...88X. Retrieved 9 February 2021.