NGC 685

NGC 685
NGC 685 by Hubble Space Telescope
Observation data (J2000 epoch)
Constellation	Eridanus
Right ascension	01^h 47^m 42.9^s[1]
Declination	−52° 45′ 42″[1]
Redshift	0.004546 ± 0.000010 [1]
Heliocentric radial velocity	1,363 ± 3 km/s[1]
Distance	50–58 Mly (15.2-17.8 Mpc)[1]
Apparent magnitude (V)	11.2[2]
Characteristics
Type	SB(rs)d [1]
Apparent size (V)	3.7′ × 3.3′[1]
Other designations
ESO 152- G 024, AM 0145-530A, IRAS 01458-5300, PGC 6581

NGC 685 is a barred spiral galaxy in the constellation Eridanus. The galaxy lies about 55 million light years away from Earth, which means, given its apparent dimensions, that NGC 685 is approximately 60,000 light years across.[1] It was discovered by John Herschel on October 3, 1834.[3]

This galaxy is seen nearly face-on, at an inclination of 23°.[4] It is a barred spiral galaxy with its bright center bar and patchy, curving arms. The arms have low surface brightness and emerge from the bar and complete three quarters of a revolution before fading.[5] The patches of bright blue along the galaxy’s arms are star clusters, groups of stars held together by their mutual gravitational attraction. Wisps of dark red near the central bar depict interstellar gas and dust, the matter from which stars form.[6] The southeast edge of the galaxy features three bright HII regions, which Halton Arp argued they are a companion galaxy. H-alpha emission is stronger at the southeastern half of the galaxy.[7] The total star formation rate of the galaxy is estimated to be 0.42 M_☉ per year.[4]

The whole galaxy is about 60,000 light-years across – a little more than half the size of our Milky Way.[6] In the centre of the galaxy is predicted to lie a supermassive black hole whose mass is estimated to be between 7.6 and 40 million solar masses, based on the spiral arm pitch angle.[8]

References

1. "NASA/IPAC Extragalactic Database". Results for NGC 685. Retrieved 1 February 2025.
2. "Revised NGC Data for NGC 685". spider.seds.org. Retrieved 30 March 2024.
3. Seligman, Courtney. "NGC 685 (= PGC 5619)". Celestial Atlas. Retrieved 19 November 2018.
4. Lee, Janice C.; et al. (1 January 2022). "The PHANGS-HST Survey: Physics at High Angular Resolution in Nearby Galaxies with the Hubble Space Telescope". The Astrophysical Journal Supplement Series. 258 (1): 10. doi:10.3847/1538-4365/ac1fe5.
5. Eskridge, Paul B.; Frogel, Jay A.; Pogge, Richard W.; Quillen, Alice C.; Berlind, Andreas A.; Davies, Roger L.; DePoy, D. L.; Gilbert, Karoline M.; Houdashelt, Mark L.; Kuchinski, Leslie E.; Ramirez, Solange V.; Sellgren, K.; Stutz, Amelia; Terndrup, Donald M.; Tiede, Glenn P. (November 2002). "Near-Infrared and Optical Morphology of Spiral Galaxies". The Astrophysical Journal Supplement Series. 143 (1): 73–111. doi:10.1086/342340.
6. This article incorporates text from this source, which is in the public domain. "Hubble Examines Entrancing Galaxy in Eridanus - NASA Science". NASA. 7 October 2023. Retrieved 1 February 2025.
7. Arp, H. (May 1982). "Characteristics of companion galaxies". The Astrophysical Journal. 256: 54. doi:10.1086/159883.
8. Davis, Benjamin L.; Berrier, Joel C.; Johns, Lucas; Shields, Douglas W.; Hartley, Matthew T.; Kennefick, Daniel; Kennefick, Julia; Seigar, Marc S.; Lacy, Claud H. S. (20 June 2014). "The Black Hole Mass Function Derived from Local Spiral Galaxies". The Astrophysical Journal. 789 (2): 124. doi:10.1088/0004-637X/789/2/124.

External links

• NGC 685 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images