Optical/IR Composite of Orion
The H_2 image of Allen and Burton (1993) [red],
combined with the new HST [S II] + [O I] image
[green] and the HST H-alpha image [blue]. The
red halo around the stars is an artifact caused
by the poorer spatial resolution of the ground-based
images. Arrows denote proper motions over the last
400 years. The major HH object groups are marked in the figure.