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September 2003

Supernova in M74

As in March's image of NGC 2841, almost all of the stars in this pair of images are in our own galaxy, lying at most a few thousand light-years away ... except for one. The arrowed star on the right-hand image appeared suddenly in January 2002, and is the light from the titanic explosion of a massive star in M74, 30,000,000 light years away. This supernova signals the violent death of a star more than 10 times more massive than our Sun. The star had exhausted all of its nuclear fuel, and tried to fuse iron nuclei in its core. This lead to a rapid collapse and then explosion, in which the star spewed out heavy elements into the interstellar medium of that galaxy.

The last such supernovae in the Milky Way was over 300 years ago, but we still see the remnants of many past supernovae, such as February's image of IC 443. But we all carry within our bones remnants of past supernovae - all elements heavier than oxygen were produced in the cores of long-dead stars, ejected into the cloud of material that eventually formed our Sun, our Earth, and us.