NGC 7635

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NGC 7635
Emission nebula
H II region
Hs-2016-13-a-large web.jpg
Widefield image of NGC 7635 as captured by the Hubble telescope.
Observation data: J2000 epoch
Right ascension 23h 20m 48.3s[1]
Declination +61° 12′ 06″[1]
Distance 7100[2] to 11000[3][4] ly   (3,400 pc)
Apparent magnitude (V) ~10[5]
Apparent dimensions (V) 15′ × 8′[6]
Constellation Cassiopeia
Physical characteristics
Radius 3[2] to 5[7][4] ly
Notable features Shell around SAO 20575[1]
Designations Bubble Nebula[1]
Sharpless 162 (Sh2-162)
Caldwell 11
See also: Lists of nebulae

NGC 7635, also known as the Bubble Nebula, Sharpless 162, or Caldwell 11, is a H II region[1] emission nebula in the constellation Cassiopeia. It lies close to the direction of the open cluster Messier 52. The "bubble" is created by the stellar wind from a massive hot, 8.7[1] magnitude young central star, SAO 20575 (BD+60°2522).[7] The nebula is near a giant molecular cloud which contains the expansion of the bubble nebula while itself being excited by the hot central star, causing it to glow.[7] It was discovered in 1787 by William Herschel.[5] The star BD+60°2522 is thought to have a mass of about 44 M.

Amateur observation[edit]

With an 8 or 10-inch (250 mm) telescope, the nebula is visible as an extremely faint and large shell around the star.[6][1] The nearby 7th magnitude star on the west hinders observation, but one can view the nebula using averted vision.[6] Using a 16 to 18-inch (460 mm) scope, one can see that the faint nebula is irregular, being elongated in the north south direction.[6]



  1. ^ a b c d e f g SIMBAD 2007.
  2. ^ a b HubbleSite 2000.
  3. ^ APOD 2004.
  4. ^ a b APOD 2006.
  5. ^ a b "NGC-IC Project Database". Retrieved 2008-12-15.[permanent dead link]
  6. ^ a b c d Kepple & Sanner 1998.
  7. ^ a b c APOD 2005.


External links[edit]