Barnard's Loop is a large shell or ring of interstellar gas. It is so large in the sky that if you held out your arm to its full length your hand couldn't cover the full nebula. The shell is expanding at 50 miles/sec (yup... miles/sec, not miles/hr) and its center is located near the Orion Nebula. The shell glows faintly in the optical and is easy to see at radio wavelengths due to the number of ions in the shell. Astronomers believe the shell is a result of the numerous supernovae explosions that have occurred in the region since star formation began some tens of millions of years ago.
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© Ronald J. Maddalena 1998