Over fifty years ago, a supernova was discovered in M83, a
spiral galaxy about 15 million light years from Earth.
Astronomers have used NASA's Chandra X-ray Observatory to make
the first detection of X-rays emitted by the debris from this
explosion. Named SN 1957D because it was the fourth supernova to
be discovered in the year of 1957, it is one of only a few
located outside of the Milky Way galaxy that is detectable, in
both radio and optical wavelengths, decades after its explosion
was observed. In 1981, astronomers saw the remnant of the
exploded star in radio waves, and then in 1987 they detected the
remnant at optical wavelengths, years after the light from the
explosion itself became undetectable. A relatively short
observation -- about 14 hours long -- from NASA's Chandra X-ray
Observatory in 2000 and 2001 did not detect any X-rays from the
remnant of SN 1957D. However, a much longer observation obtained
in 2010 and 2011, totaling nearly 8 and 1/2 days of Chandra
time, did reveal the presence of X-ray