Update on 27 October: Another high-mass pulsar weighing 1.97 solar masses was reported by a team led by Paul Demorest of the National Radio Astronomy Observatory in Charlottesville, Virginia (Nature, vol 467, p 1081). Although the calculated mass for that pulsar, called J1614-2230, is lower than that of the black widow pulsar, the uncertainty in the measurement is smaller: +/- 0.04 solar masses vs 0.12 solar masses for the black widow pulsar.
A CANNIBALISTIC collapsed star is growing so fat from the partner it is slowly devouring that it is likely to be the most massive neutron star yet measured. The observation suggests that neutron stars can grow much bigger than previously thought before collapsing to become a black hole.
The star in question is a 鈥渂lack widow鈥� pulsar, a type of rotating neutron star that is highly magnetised. It rotates in tandem with a smaller partner, which its gravitational field slowly destroys.
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Previously the most massive neutron star known was between 1.66 and 1.68 times as massive as the sun. Now Marten van Kerkwijk of the University of Toronto, Canada, and his colleagues estimate that the black widow pulsar B1957+20 (depicted right) is 2.4 solar masses ().
This rules out the popular 鈥淏rown-Bethe鈥� model, which says the maximum mass for a neutron star is about 1.5 solar masses before collapse into a black hole is inevitable, as well as other models.
鈥淭wo solar masses would exclude a whole bunch of models and 2.4 solar masses would blow just about anything away,鈥� says co-author of the California Institute of Technology in Pasadena.
