The day the supernova exploded (a) it was surrounded by a shell of matter ejected a month earlier (purple) with a radius of 7,000,000,000 kilometers, moving 2,000 kilometers a second. An outer shell (orange) had been ejected earlier and was moving slower. By day 5 (b) the shock front (black circle) was moving 10,000 kilometers a second, and by day 20 (c) had engulfed the inner shell, exposing the debris of the exploded core. (Sketch adapted from Ofek et al, Palomar Transient Factory)
The Palomar Transient Factory (PTF) brings together universities, observatories, and one national laboratory to hunt for supernovae and other astronomical objects. At the National Energy Research Scientific Computing Center (NERSC) Berkeley Lab processes and stores the data from PTF's surveys, which use the Oschin Telescope at Caltech's Palomar Observatory. On August 25, 2010, PTF's "autonomous machine-learning framework," developed by Josh Bloom of Berkeley Lab's Physics Division and Peter Nugent of the Computational Research Division (both are also with UC Berkeley's Department of Astronomy) and their colleagues, was combing through recent data and came upon a Type IIn supernova, half a billion light years away in the constellation Hercules. The supernova was eventually labeled SN 2010mc. Type II's are "core collapse" supernovae, which start as precursor stars somewhere between 8 and 100 times the mass of Earth's sun, burning much of their hydrogen down to helium, carbon, and other elements and eventually to an iron cinder. When this core reaches 1.4 solar masses, it collapses under its own weight to create a neutron star or even a black hole, releasing a tremendous amount of energy as neutrinos, magnetic fields, and shock waves - and destroying the star. Astronomers have long suspected the story isn't that simple, that the explosion of a Type II supernova is only the last in a series of smaller blasts that successively blow off much of the core's enveloping matter.
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