NGC 1931

NGC 1931 is a reflection and emission nebula and around a young star cluster in the constellation Auriga. The nebula shares similarities to the Orion Nebula as it is a mixed emission-reflection nebula that also contains a small Trapezium of hot young stars.^[2] At around 2 million years of age,^[3] most of the ongoing star formation in the star cluster is hidden away in the nebula.^[4] It is believed that the main ionizing source for the dusty molecular cloud is a single, hot B-type star.^[3] The distance from Earth is estimated at 7500 light years.^[4]

NGC 1931

Reflection nebula
emission nebula
NGC 1931
Observation data: J2000.0 epoch
Right ascension	5h 31m [1]
Declination	+34° 15′[1]
Distance	~7500 ly
Apparent magnitude (V)	10.1[1]
Apparent dimensions (V)	7′
Constellation	Auriga
See also: Lists of nebulae

History

The German-born English astronomer William Herschel discovered the small reflection nebula in 1793 and noted seeing a few stars in the middle.^[5] In 1931, Swedish astronomer Per Collinder included it in his catalog of open star clusters as the "nebulous cluster" Collinder 68.^[6] American astronomer Stewart Sharpless cataloged the emission component, which lies outside the center, as Sh 2-237 in 1959.^[7]