Celestial Objects

Caldwell 4

Nebulae

Citation Formats

General Reference

Space and Astronomy Atlas. "Caldwell 4." Accessed September 2, 2026. https://space.interactiveatlas.org/celestial-objects/caldwell-4.

APA Style

Space and Astronomy Atlas. (n.d.). Caldwell 4. Retrieved September 2, 2026, from https://space.interactiveatlas.org/celestial-objects/caldwell-4

BibTeX

@misc{spaceandastronomyatlas-caldwell-4,
  author = {Space and Astronomy Atlas},
  title = {Caldwell 4},
  year = {2026},
  url = {https://space.interactiveatlas.org/celestial-objects/caldwell-4},
  note = {Accessed September 2, 2026}
}

Caldwell 4, also known as the Iris Nebula or NGC 7023, is a reflection nebula in the constellation Cepheus, discovered by William Herschel in 1794. Starlight from a young, hot star embedded within it, SAO 19158, scatters off surrounding dust to produce the nebula's characteristic blue glow, and it lies roughly 1,300 light-years from Earth.

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