Signs of Collapse

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Science  22 Sep 2006:
Vol. 313, Issue 5794, pp. 1705
DOI: 10.1126/science.313.5794.1705b

When their nuclear fuel is exhausted, stars die, and the residual iron core collapses on itself. The outcome of a star's death throes depends on mass, however. Stars with between 10 and 20 times the mass of the Sun collapse in a spectacular explosion known as a supernova, leaving behind a neutron star, whereas those larger than 20 solar masses implode to form black holes in a “hypernova.” In both cases, copious bursts of neutrinos are released along with optical, x-ray, and gamma radiation. Most scenarios for hypernova collapse involve rapidly rotating stars, but recent studies indicate that some massive stars may be rotating only slowly or not at all.

Sumiyoshi et al. have carried out simulations showing that such stars may lead to explosions that are very dim in the electromagnetic spectrum, but that still lead to black hole formation and powerful neutrino bursts. These neutrino signals are sensitive indicators of the equation of state of matter in the collapsed star. (The equation of state relates basic quantities such as pressure, density, and temperature.) As a result, these neutrino bursts could offer a valuable diagnostic tool for studying the properties of stellar matter. — DV

Phys. Rev. Lett. 97, 091101 (2006).

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