Monkey Head Nebula

Deep within the constellation of Orion, roughly 6,400 light-years from Earth, lies a vast cloud of glowing gas that astronomers have nicknamed the Monkey Head Nebula. Its whimsical name comes from the resemblance some observers see to the face of a monkey when the nebula is imaged in visible light.

NGC 2174 is an H II region — a massive stellar nursery where young, hot stars are continuously being born. The primary energy source is HD 42088, an O-type star with a surface temperature of around 39,500 K and a luminosity exceeding 8,200 times that of the Sun. Its intense ultraviolet radiation ionizes the surrounding hydrogen gas, causing the nebula to glow with the characteristic light of an emission nebula.

Spanning approximately 40 arcminutes across the sky — larger than the full Moon — NGC 2174 extends some 75 light-years in physical space. It is closely associated with the open cluster NGC 2175, whose very young stars — only around 9 million years old — are actively sculpting and eroding the dust pillars that give the nebula its distinctive appearance.

The nebula was first discovered on February 6, 1877, by French astronomer Édouard Stephan at the Marseille Observatory. In 2014, NASA's Hubble Space Telescope chose NGC 2174 as the subject of its 24th anniversary image, revealing extraordinary detail in the pillars of star formation within.