IC 342 (also known as Caldwell 5) is an intermediate spiral galaxy in the constellation Camelopardalis, located relatively close to the Milky Way. Despite its size and actual brightness, its location in dusty areas near the galactic equator makes it difficult to observe, leading to the nickname "The Hidden Galaxy", though it can readily be detected even with binoculars. If the galaxy were not obscured, it would be visible by naked eye. The dust makes it difficult to determine its precise distance; modern estimates range from about 7 Mly to about 11 Mly. The galaxy was discovered by William Frederick Denning in 1892. It is one of the brightest in the IC 342/Maffei Group, one of the closest galaxy groups to the Local Group. Edwin Hubble first thought it to be in the Local Group, but it was later determined not to be a member.
|Observation data (J2000 epoch)|
|Right ascension||03h 46m 48.5s|
|Declination||+68° 05′ 46″|
|Redshift||31 ± 3 km/s|
|Distance||10.7 ± 0.9 Mly (3.3 ± 0.3 Mpc)|
|Apparent magnitude (V)||9.1|
|Number of stars||100 billion|
|Apparent size (V)||21′.4 × 20′.9|
|UGC 2847, PGC 13826, Caldwell 5|
In 1935, Harlow Shapley found that it was wider than the full moon, and by angular size the third-largest spiral galaxy then known, smaller only than the Andromeda Galaxy (M31) and the Triangulum Galaxy (M33). (Modern estimates are more conservative, giving the apparent size as one-half to two-thirds the diameter of the full moon).
It has an H II nucleus. The galaxy has a diameter of 75 000 light-years.
In 2020, the galaxy KKH 32 was identified as the first known satellite of IC 342 that is a dwarf spheroidal galaxy. Unlike galaxies with large bulges such as the Andromeda Galaxy, IC 342 has a relatively few dwarf satellite galaxies. KKH 32 is located about 10.2 million light-years (3.12 megaparsecs) away, and has a diameter of about 4,300 light-years (1.32 kiloparsecs).
- NGC 6946 - similar galaxy heavily obscured by Milky Way stars and dust.
- "NASA/IPAC Extragalactic Database". Results for IC 342. Retrieved 2006-11-01.
- I. D. Karachentsev; V. E. Karachentseva; W. K. Hutchmeier; D. I. Makarov (2004). "A Catalog of Neighboring Galaxies". Astronomical Journal. 127 (4): 2031–2068. Bibcode:2004AJ....127.2031K. doi:10.1086/382905.
- Karachentsev, I. D.; Kashibadze, O. G. (2006). "Masses of the local group and of the M81 group estimated from distortions in the local velocity field". Astrophysics. 49 (1): 3–18. Bibcode:2006Ap.....49....3K. doi:10.1007/s10511-006-0002-6. S2CID 120973010.
- "Hubble's Hidden Galaxy". www.spacetelescope.org. Retrieved 3 July 2017.
- O'Meara, Stephen James (2002). The Caldwell Objects. Cambridge University Press. pp. 30–32. ISBN 0-933346-97-2.
- Nemiroff, R.; Bonnell, J., eds. (22 December 2010). "Hidden Galaxy IC 342". Astronomy Picture of the Day. NASA. Retrieved 28 January 2013.
- Denning, W. F. (1893). "New nebula". Astronomy and Astro-Physics. 12: 189. Bibcode:1893AstAp..12..189D.
- SEDS IC 342. Archived January 2, 2007, at the Wayback Machine
- Border Cities Star (Windsor, Ontario), "Spiral Galaxy Third Biggest", 24 June 1935, p.8
- Ho, Luis C.; Filippenko, Alexei V.; Sargent, Wallace L. W. (1997). "A Search for 'Dwarf' Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies". Astrophysical Journal Supplement. 112 (2): 315–390. arXiv:astro-ph/9704107. Bibcode:1997ApJS..112..315H. doi:10.1086/313041. S2CID 17086638.
- Karachentsev, Igor D.; Makarova, Lidia N.; Tully, R. Brent; Anand, Gagandeep S.; Rizzi, Luca; Shaya, Edward J.; Afanasiev, Viktor L. (2020). "KKH 22, the first dwarf spheroidal satellite of IC 342". Astronomy & Astrophysics. 638: A111. arXiv:2005.03132. Bibcode:2020A&A...638A.111K. doi:10.1051/0004-6361/202037993. S2CID 218538458.
|Wikimedia Commons has media related to IC 342.|
- NASA Astronomy Picture of the Day – 22 December 2010
- IC 342 (image included)
- IC 342 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images