Bubble Nebula

NGC 7635, also known as the Bubble Nebula, Sharpless 162, or Caldwell 11, is an H II region[1] emission nebula in the constellation Cassiopeia. It lies close to 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 November 1787 by William Herschel.[5] The star BD+60°2522 is thought to have a mass of about 44 M☉.

For the Bubble Nebula in Barnard's Galaxy, see Bubble Nebula (NGC 6822).
NGC 7635
Emission nebula
H II region
Wide field image of NGC 7635 as captured by the Hubble Space Telescope
Observation data: J2000 epoch
Right ascension23h 20m 48.3s[1]
Declination+61° 12′ 06″[1]
Distance7100[2] to 11000[3][4] ly   (3,400 pc)
Apparent magnitude (V)~10[5]
Apparent dimensions (V)15′ × 8′[6]
ConstellationCassiopeia
Physical characteristics
Radius3[2] to 5[7][4] ly
Notable featuresShell around SAO 20575[1]
DesignationsBubble Nebula[1]
Sharpless 162 (Sh2-162)
Caldwell 11

Amateur observation
NGC 7635 and its environs imaged through an 8-inch amateur telescope

With an 8-or-10-inch (200 or 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 (410 to 460 mm) scope, one can see that the faint nebula is irregular, being elongated in the north south direction.[6]

See also

Notes
  1. SIMBAD 2007.
  2. HubbleSite 2000.
  3. Nemiroff & Bonnell 2004.
  4. Nemiroff & Bonnell 2006.
  5. "NGC-IC Project Database". Archived from the original on 2001-09-04. Retrieved 2008-12-15.
  6. Kepple & Sanner 1998.
  7. Nemiroff & Bonnell 2005.

References
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