 The current astronomical model for the nebula consists of an ionized ( H II ) region , roughly centered on Theta1 Orionis C , which lies on the side of an elongated molecular cloud in a cavity formed by the massive young stars . ( Theta1 Orionis C emits 3 @-@ 4 times as much photoionizing light as the next brightest star , Theta2 Orionis A. ) The H II region has a temperature ranging up to 10 @,@ 000 K , but this temperature falls dramatically near the edge of the nebula . The nebulous emission comes primarily from photoionized gas on the back surface of the cavity . The H II region is surrounded by an irregular , concave bay of more neutral , high @-@ density cloud , with clumps of neutral gas lying outside the bay area . This in turn lies on the perimeter of the Orion Molecular Cloud . The gas in the molecular cloud displays a range of velocities and turbulence , particularly around the core region . Relative movements are up to 10 km / s ( 22 @,@ 000 mi / h ) , with local variations of up to 50 km / s and possibly more . 
