NGC 7635

NGC 7635
Emission nebula
H II region

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

NGC 7635, also called 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

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]

Notes

  1. 1 2 3 4 5 6 7 SIMBAD 2007.
  2. 1 2 HubbleSite 2000.
  3. ↑ APOD 2004.
  4. 1 2 APOD 2006.
  5. 1 2 "NGC-IC Project Database". Retrieved 2008-12-15.
  6. 1 2 3 4 Kepple & Sanner 1998.
  7. 1 2 3 APOD 2005.

References

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