* Astronomy

NGC 604 (also IRAS 01317+3031) is a magnitude +12.0 H II region located 2.7 million light-years away inside the Triangulum Galaxy (M33) in the constellation Triangulum.

The emission nebula was discovered by German-British astronomer William Herschel using a 47.5 cm (18.7 inch) f/13 speculum reflector at Datchet, Berkshire on the 11th September 1784.

Right Ascension 01h 34m 33.2s, Declination +30° 47' 06"

 It is one of the largest H II regions in the Local Group of galaxies; at the galaxy's estimated distance of 2.7 million light-years its longest diameter is roughly 1500 light years (460 parsecs), over 40 times the size of the visible portion of the Orion Nebula. It is over 6300 times more luminous than the Orion Nebula, and if it were at the same distance it would outshine Venus.
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 When William Herschel compiled his extensive catalogue of nebulae, he was careful not to include most of the objects identified by Messier. However, M33 was an exception and he catalogued this object on September 11, 1784 as H V-17.
Herschel also catalogued the Triangulum Galaxy's brightest and largest H II region (diffuse emission nebula containing ionised hydrogen) as H III.150 separately from the galaxy itself, which eventually obtained NGC number 604. 
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