|Observation data: J2000 epoch|
|Right ascension||06h 09.7m|
|Distance||6,400 ly (2,000 pc)|
|Apparent magnitude (V)||6.8|
|Apparent dimensions (V)||40′|
|See also: Diffuse nebula, Lists of nebulae|
NGC 2174 (also known as Monkey Head Nebula) is an H II emission nebula located in the constellation Orion and is associated with the open star cluster NGC 2175. It is thought to be located about 6,400 light-years away from Earth. The nebula may have formed through hierarchical collapse.
There is some equivocation in the use of the identifiers NGC 2174 and NGC 2175. These may apply to the entire nebula, to its brightest knot, or to the star cluster it includes. Burnham's Celestial Handbook lists the entire nebula as 2174/2175 and does not mention the star cluster. The NGC Project (working from the original descriptive notes) assigns NGC 2174 to the prominent knot at J2000 06h 09m 23.7s, +20° 39′ 34″ and NGC 2175 to the entire nebula, and by extension to the star cluster. Simbad uses NGC 2174 for the nebula and NGC 2175 for the star cluster. 
- "SIMBAD Astronomical Database". Results for NGC 2174. Retrieved 2011-07-13.
- Cotera, A.; Hester, J.; Healy, K.; Snider, K.; Simpson, J.; Whitney, B. (2006). "Using Spitzer IRAC observations to Compare Modes of Star Formation in G305.35+0.7 and NGC 2174/5". Triggered Star Formation in a Turbulent ISM, International Astronomical Union. Symposium no. 237, held 14–18 August 2006 in Prague, Czech Republic, S237, #98. Bibcode:2006IAUS..237E..98C.[dead link]
- Robert Burnham, Jr, Burnham's Celestial Handbook, Dover, 1978, p. 1280.
- "Public Database". NGC/IC Project. Results for NGC 2174 and NGC 2175. Retrieved 12 January 2014.
- "SIMBAD Astronomical Database". Results for NGC 2175. Retrieved 2014-01-13.
- NGC 2174: Emission Nebula in Orion, 2008/6/12 Astronomy Picture of the Day
- NGC 2174: Stars Versus Mountains, 2011/2/9 Astronomy Picture of the Day