NGC 604, one of largest nebulae (H II region) is located in the Triangulum Galaxy (viewed by the Hubble Space Telescope).
Below is a list of the largest known nebulae so far discovered, ordered by actual diameter. This list is prone to change because of inconsistencies between studies, the great distances of nebulae from our stellar neighborhood, and the constant refinement of technology and engineering.
Nebulae have no standardized boundaries, so the measurements are subject to revision. Lastly, scientists are still defining the features and parameters of nebulae. Because of these rapid developments and adjustments, this list might be potentially unreliable.
↑Those measurements are based on an apparent diameter of 480 arcminutes (') plus an assumed distance of 1.5 kpc and the current distance of VY CMa which is about 1.17 kpc as the nebula is sometimes found to have the same distance as VY CMa.
↑Lockman, Felix J.; Benjamin, Robert A.; Heroux, A. J.; Langston, Glen I. (May 2008). "The Smith Cloud: A High-Velocity Cloud Colliding with the Milky Way". The Astrophysical Journal679 (1): L21. doi:10.1086/588838. Bibcode: 2008ApJ...679L..21L.
↑Barba, Rodolfo (2004). "An in-depth analysis of a prototypical giant H II region: NGC 604". HST Proposal ID #10419: 10419. Bibcode: 2004hst..prop10419B.
↑Sushch, I.; Hnatyk, B.; Neronov, A. (2011). "Modeling of the Vela complex including the Vela supernova remnant, the binary system γ2 Velorum, and the Gum nebula". Astronomy and Astrophysics525: A154. doi:10.1051/0004-6361/201015346. Bibcode: 2011A&A...525A.154S.
↑O'Dell, C.R.; Ferland, G.J.; Porter, R.L.; van Hoof, P.A.M. (2011). "Physical Conditions in Barnard's Loop, Components of the Orion-eridanus Bubble, and Implications for the Warm Ionized Medium Component of the Interstellar Medium". The Astrophysical Journal733 (1): 9. doi:10.1088/0004-637X/733/1/9. Bibcode: 2011ApJ...733....9O.
↑Reipurth, B. (December 2008). "The Young Cluster NGC 6604 and the Serpens OB2 Association". Handbook of Star Forming Regions, Volume II: The Southern Sky5: 590. Bibcode: 2008hsf2.book..590R.
↑O'Dell, C. R.; McCullough, Peter R.; Meixner, Margaret (2004). "Unraveling the Helix Nebula: Its Structure and Knots". The Astronomical Journal128 (5): 2339–2356. doi:10.1086/424621. Bibcode: 2004AJ....128.2339O.
↑Abraham, Zulema; Falceta-Gonçalves, Diego; Beaklini, Pedro P. B. (2014). "Η Carinae Baby Homunculus Uncovered by A/km/kmLMA". The Astrophysical Journal791 (2): 95. doi:10.1088/0004-637X/791/2/95. Bibcode: 2014ApJ...791...95A.
Cannon, John M.; Walter, Fabian; Armus, Lee; Bendo, George J.; Calzetti; Draine, Bruce T.; Engelbracht, Charles W.; Helou, George et al. (December 2006), "The Nature of Infrared Emission in the Local Group Dwarf Galaxy NGC 6822 as Revealed by Spitzer", The Astrophysical Journal652 (2): 1170–1187, doi:10.1086/508341, Bibcode: 2006ApJ...652.1170C
Karachentsev, I. D.; Karachentseva, V. E.; Hutchmeier, W. K.; Makarov, D. I. (April 2004), "A Catalog of Neighboring Galaxies", Astronomical Journal127 (4): 2031–2068, doi:10.1086/382905, Bibcode: 2004AJ....127.2031K
Karachentsev, I. D.; Kashibadze, O. G. (January 2006), "Masses of the local group and of the M81 group estimated from distortions in the local velocity field", Astrophysics49 (1): 3–18, doi:10.1007/s10511-006-0002-6, Bibcode: 2006Ap.....49....3K