Barnard's Loop is a ring of ionised gas that appears to surround the Flame (Sh 2-277) and Orion (Sh 2-281) nebulae and is the brightest portion of the much larger
Orion-Eridanus superbubble. Many researchers assume that Barnard's Loop is physically associated with these nebulae and the Orion molecular clouds. However, a 2005 study argues that Barnard's Loop is considerably closer than the gas that makes up the main portion of the Orion molecular clouds.
This image shows only a small portion of the nebula. You can see
the full Loop here.
Barnard's Loop is the ionised gas that makes up the nearest portion of the Orion Eridanus bubble. It is considerably closer than the gas that makes up the main portion of the Orion molecular clouds.[
1]
Barnard's Loop is associated with the main Orion molecular clouds. [
2]
Notes
1. ^ Wilson, B. A., Dame, T. M., Masheder, M. R. W., et al. (2005). "A uniform
CO survey of the molecular clouds in Orion and Monoceros", Astronomy and
Astrophysics, Vol. 430, 523-539. [2005A&A...430..523W]
2. ^ O'Dell, C. R., Ferland, G. J., Porter, R. L., et al. (2011). "Physical
Conditions in Barnard's Loop, Components of the Orion-eridanus Bubble, and
Implications for the Warm Ionized Medium Component of the Interstellar
Medium", The Astrophysical Journal, Vol. 733, 9. [2011ApJ...733....9O]