Black Holes

The spinning heart of the Einstein Cross

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Science  12 Sep 2014:
Vol. 345, Issue 6202, pp. 1307-1308
DOI: 10.1126/science.345.6202.1307-d

Supermassive black holes power entire galaxies from their cores, but how they grew so large is uncertain. When astronomers describe a black hole, they rely on two features: its mass and how fast it spins. The spin rate provides information about how the black hole grew, but it is tricky to measure. Reynolds et al. have determined the spin for the most distant quasar yet, a source called the Einstein Cross. This source got its name because the quasar's light is bent around a massive galaxy and reimaged four times. The high spin rate suggests that several dramatic accretion events produced the black hole rather than many small ones.

Astrophys. J. Lett. 10.1088/2041-8205/792/1/L19 (2014).

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