Bright Young Thing

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Science  20 Dec 2013:
Vol. 342, Issue 6165, pp. 1418-1419
DOI: 10.1126/science.342.6165.1418-e

Circinus X-1, a binary star system that includes a neutron star, is one of the brightest x-ray sources in the sky. Heinz et al. now report that this x-ray binary is the youngest known yet. Data from the Chandra X-ray Observatory and from the Australian Telescope Compact Array, a radio telescope composed of six 22-m antennas, show that the neutron star is still within the supernova remnant in which it was born. A supernova remnant, the radiating material that is left after a star explodes at the end of its life, does not stay visible for very long. In this case, the age of the remnant constrains Circinus' age to less than 4600 years. Such a young age explains the system's rapid orbital evolution and highly eccentric orbit, which had been puzzling. There has not been enough time yet for the orbit to be tidally circularized from the eccentricity it received in the explosion. Because the neutron star is known to have a low magnetic field, the young age also implies that neutron stars can be born with low magnetic fields or can easily become demagnetized.

Astrophys. J. 779, 171 (2013).

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