IC 342

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",[4][1] though it can readily be detected even with binoculars.[5] 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[6] to about 11 Mly.[2] The galaxy was discovered by William Frederick Denning in 1892.[7] 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.[8]

IC 342
IC 342 imaged with a 102mm telescope.
Observation data (J2000 epoch)
ConstellationCamelopardalis
Right ascension03h 46m 48.5s[1]
Declination+68° 05′ 46″[1]
Redshift31 ± 3 km/s[1]
Distance10.7 ± 0.9 Mly (3.3 ± 0.3 Mpc)[2][3]
Apparent magnitude (V)9.1[1]
Characteristics
TypeSAB(rs)cd[1]
Number of stars100 billion
Apparent size (V)21′.4 × 20′.9[1]
Other designations
UGC 2847, PGC 13826,[1] 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).[9] (Modern estimates are more conservative, giving the apparent size as one-half to two-thirds the diameter of the full moon).[1][5]

It has an H II nucleus. The galaxy has a diameter of 75 000 light-years.[10]

  • IC 342, the "Hidden Galaxy." LRGBHa image by W4SM with 17" PlaneWave CDK
  • Hubble Space Telescope image of the central region of IC 342, showing the central star cluster and surrounding dust lanes.[4]
  • IC 342 seen by the Spitzer Space Telescope
  • Caldwell 5 (IC 342) as photographed by the Spitzer Space Telescope. Not related stars have been edited out.

See also
  • NGC 6946 - similar galaxy heavily obscured by Milky Way stars and dust.

References
  1. "NASA/IPAC Extragalactic Database". Results for IC 342. Retrieved 2006-11-01.
  2. 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.
  3. 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.
  4. "Hubble's Hidden Galaxy". www.spacetelescope.org. Retrieved 3 July 2017.
  5. O'Meara, Stephen James (2002). The Caldwell Objects. Cambridge University Press. pp. 30–32. ISBN 0-933346-97-2.
  6. Nemiroff, R.; Bonnell, J., eds. (22 December 2010). "Hidden Galaxy IC 342". Astronomy Picture of the Day. NASA. Retrieved 28 January 2013.
  7. Denning, W. F. (1893). "New nebula". Astronomy and Astro-Physics. 12: 189. Bibcode:1893AstAp..12..189D.
  8. SEDS IC 342. Archived January 2, 2007, at the Wayback Machine
  9. Border Cities Star (Windsor, Ontario), "Spiral Galaxy Third Biggest", 24 June 1935, p.8
  10. 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.


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