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.[4] 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.[5]SIMBAD uses NGC 2174 for the nebula and NGC 2175 for the star cluster.[1][6]
Glowing gas and dark dust do not survive well in the Monkey Head Nebula. Young stars near the center of the nebula generate stellar winds and high energy radiation that causes the nebula's material to shift into complex shapes.[7] The nebula is primarily composed of hydrogen which glows at infrared wavelengths due to the radiation.[8]
^Cotera, A.; Hester, J.; Healy, K.; Snider, K.; et al. (August 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. Prague, Czech Republic (published 2006). Bibcode:2006IAUS..237E..98C. S237, #98.[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. Archived from the original on 28 May 2009. Retrieved 12 January 2014.
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Infrared image of NGC 2174 as viewed by the Spitzer Space Telescope
Monkey Head Nebula in Narrowband Sulfur-Hydrogen Alpha- Oxygen with a 1000mm telescope
Monkey Head Nebula in hydrogen alpha focal length 384mm
Monkey Head Nebula in bi-color with a 384mm telescope
Monkeyhead nebula taken with a 140mm refractor by amateur astronomer Mark Johnston
NGC 2174 (Monkey Head Nebula) in SHO palette by W4SM, 17" PlaneWave CDK scope, Louisa, VA
