Chandra X-ray image of G21.5-0.9_chandra.jpg
Credit: NASA/CXC/U.Manitoba/H.Matheson & S.Safi-Harb

Finding a Crab's Shell

Sometimes it's what's on the outside that counts. This seems to be the case with G21.5-0.9, a supernova remnant identified 30 years ago by radio astronomers. G21.5-0.9 is (or was) a mysterious member of the class of so-called "Crab-like" (or plerionic) supernova remnants, one (like the class namesake, the Crab Nebula itself) lacking an outer "shell" where the supernova blast wave shocks the interstellar medium. The lack of a shell is a surprise and not well understood. But a deep image of G21.5-0.9 (shown above) by the Chandra X-ray Observatory has helped resolve the mystery, at least in this one particular case. The Chandra observations show that G21.5-0.9 is indeed surrounded by a shell of X-ray emitting plasma. The Chandra data helps pinpoint the total amount of energy in the original explosion, as well as helping to determine when the star blew up.

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Page Author: Dr. Michael F. Corcoran
Last modified Friday, 20-Apr-2012 15:24:07 EDT