NGC 2404

NGC 2404 is massive H II region inside NGC 2403, a spiral galaxy in Camelopardalis. It was discovered on February 2, 1886 by Gulliaume Bigourdan. NGC 2404 is approximately ≈ 2000 ly in diameter, making it one of the largest H II regions so far known. NGC 2404 is even larger than the Tarantula Nebula, one of the largest and most active H II regions in Local Group. NGC 2404 is 83 times larger than Orion Nebula, and if it would be at same distance, it would cause visible shadows. It is the largest H II region in NGC 2403, and lies at the outskirts of the galaxy, making striking similarity with NGC 604 in M33, both in size and location in host galaxy. This H II region contains 30-40 Wolf-Rayet stars,[2] and unlike Tarantula Nebula, but similar to NGC 604, the NGC 2404's open cluster is probably much less compact, so it probably looks like as a large stellar association. This H II region is probably only a few million years old.

NGC 2404
Emission nebula
H II region
NGC 2404 is the giant H II region to the left
Observation data: J2000 epoch
Right ascension07h 36m 51.4s[1]
Declination+65° 36′ 09″[1]
Distance8,000,000 ly   (2,454,000 pc)
Apparent magnitude (V)+16.9
ConstellationCamelopardalis
Physical characteristics
Radius≈ 1000 ly
Absolute magnitude (V)-14.5
Notable featuresMassive H II region,
the largest one in NGC 2403.

References
  1. "NASA/IPAC Extragalactic Database". Results for NGC 2403. Retrieved 2006-11-21.
  2. Finlay, W. H. (April 18, 2006). Concise Catalog of Deep-sky Objects: Astrophysical Information for 500 Galaxies, Clusters and Nebulae. Springer Science & Business Media. ISBN 9781852338510 – via Google Books.
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