Why is the belt of Orion [ http://www.daviddar…] surrounded by a bubble? Although glowing like an emission nebula [ http://antwrp.gsfc.…], the origin of the bubble, known as Barnard's Loop [ http://weblore.com/…], is currently unknown. Progenitor hypotheses include the wind [ http://www-spof.gsf…]s from bright Orion stars and the supernovas [ http://heasarc.gsfc…] of stars long gone. Barnard's Loop [ http://www.seds.org…] is too faint to be identified with the unaided eye. The nebula [ http://eaa.iop.org/…] was discovered only in 1895 by E. E. Barnard [ http://astro.uchica…] on long duration film exposures. Orion's belt [ http://www.gb.nrao.…] is seen as the three bright stars across the center of the image, the upper two noticeably blue. Just to the right of the lowest star in Orion's belt [ http://www.astro.ui…] is a slight indentation in an emission nebula that, when seen at higher magnification [ http://antwrp.gsfc.…], resolves into the Horsehead Nebula [ http://antwrp.gsfc.…]. To the right of the belt stars is the bright, famous, and photogenic Orion Nebula [ http://antwrp.gsfc.…].
Explanation
Why is the belt of Orion [ http://www.daviddar…] surrounded by a bubble? Although glowing like an emission nebula [ http://antwrp.gsfc.…], the origin of the bubble, known as Barnard's Loop [ http://weblore.com/…], is currently unknown. Progenitor hypotheses include the wind [ http://www-spof.gsf…]s from bright Orion stars and the supernovas [ http://heasarc.gsfc…] of stars long gone. Barnard's Loop [ http://www.seds.org…] is too faint to be identified with the unaided eye. The nebula [ http://eaa.iop.org/…] was discovered only in 1895 by E. E. Barnard [ http://astro.uchica…] on long duration film exposures. Orion's belt [ http://www.gb.nrao.…] is seen as the three bright stars across the center of the image, the upper two noticeably blue. Just to the right of the lowest star in Orion's belt [ http://www.astro.ui…] is a slight indentation in an emission nebula that, when seen at higher magnification [ http://antwrp.gsfc.…], resolves into the Horsehead Nebula [ http://antwrp.gsfc.…]. To the right of the belt stars is the bright, famous, and photogenic Orion Nebula [ http://antwrp.gsfc.…].
