Some cosmic lighthouses are a little bit weird
(Image: NASA)

Astrophile: Split personality tarnishes pulsars’ rep

19:00 24 January 2013 by Jacob Aron

Object: Pulsar (pulsing star)
Behaviour: Erratic

A split personality can be disturbing, especially when it affects someone you least expected it to. Now it seems stars, too, can have disturbingly fractured personas. The discovery of the first pulsar that shines at different frequencies at different times is tarnishing the reputation of this class of pulsing dead star. Until now, pulsars have been relied upon as cosmic timekeepers, but perhaps we can’t take their regularity for granted any longer.

We had thought of pulsars – the dense remnants of exploded stars – as emitting radio waves, X-rays or gamma rays in bursts of such regularity that you could practically set your watch by them. Pulsars are spinning neutron stars, with strong magnetic fields that emit beams of radiation from their poles. The poles are offset from the axis of rotation – just as the magnetic poles on Earth do not line up with true north and south. This offset means the beams sweep around like a lighthouse as the pulsar rotates, giving the star’s radiation a distinctive pulse when viewed from a distance.

Individual pulsars can emit radiation at a range of frequencies, from radio waves to gamma rays, and some radio pulsars have been seen to dim or even stop broadcasting all together. That finding had previously cast some doubt on pulsars’ otherwise impeccable reputation for dependability.

The latest discovery takes that to a new level, though. When Wim Hermsen of the Netherlands Institute for Space Research in Utrecht and colleagues took the first simultaneous measurements of both the radio and gamma radiation from B0943+10, a pulsar known to emit at both frequencies, they got a shock.

Read more: Astrophile: Split personality tarnishes pulsars' rep – space – 24 January 2013 – New Scientist.

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