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☉.
| Emission nebula | |
|---|---|
| H II region | |
 Wide field image of NGC 7635 as captured by the Hubble Space 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 |
Amateur observation
edit
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
editNotes
edit- ^ a b c d e f g SIMBAD 2007.
- ^ a b HubbleSite 2000.
- ^ Nemiroff & Bonnell 2004.
- ^ a b Nemiroff & Bonnell 2006.
- ^ a b "NGC-IC Project Database". Archived from the original on 2001-09-04. Retrieved 2008-12-15.
- ^ a b c d Kepple & Sanner 1998.
- ^ a b c Nemiroff & Bonnell 2005.
References
edit- SIMBAD (February 23, 2007). "Results for NGC 7635". SIMBAD, Centre de Données Astronomiques de Strasbourg.
- Kepple, George Robert; Sanner, Glen W. (1998). The Night Sky Observer's Guide. Vol. 1. Willmann-Bell, Inc. pp. 108–109. ISBN 978-0-943396-58-3.
- HubbleSite (2000). "An Expanding Bubble in Space".
- Nemiroff, R.; Bonnell, J., eds. (July 16, 2004). "The Bubble". Astronomy Picture of the Day. NASA.
- Nemiroff, R.; Bonnell, J., eds. (November 7, 2005). "NGC 7635: The Bubble Nebula". Astronomy Picture of the Day. NASA.
- Nemiroff, R.; Bonnell, J., eds. (October 18, 2006). "NGC 7635: The Bubble". Astronomy Picture of the Day. NASA.
External links
edit
