Bubble Nebula
emission nebula in the constellation Cassiopeia
The Bubble Nebula, also known as NGC 7635, Sharpless 162, or Caldwell 11, is an H II region 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 magnitude young central star, SAO 20575 (BD+60°2522). 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. It was discovered in November 1787 by William Herschel. The star BD+60°2522 is thought to have a mass of about 44 M☉.
Amateur observation
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. The nearby 7th magnitude star on the west hinders observation, but one can view the nebula using averted vision. 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.
This brief starts where responsible research should: with the source description of “Bubble Nebula” as emission nebula in the constellation Cassiopeia. Everything that follows is an evidence route, not borrowed authority.
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The subject matters to the general reference register because the source frames it as emission nebula in the constellation Cassiopeia. Its deeper value depends on whether names, dates, institutions and citations support that framing.
The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Jul 24, 2026. The linked authority identifier is Q725471. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1787.
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This entry incorporates text from “Bubble Nebula” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.