A pulsar with glowing cones of radiation stemming from its magnetic poles. New observations reported in Science re-open an old debate about how these spinning stars work. (Credit: European Space Agency/ATG medialab)  enlarge

Jan. 24, 2013 — Pulsars — tiny spinning stars, heavier than the sun and smaller than a city — have puzzled scientists since they were discovered in 1967.

Now, new observations by an international team, including University of Vermont astrophysicist Joanna Rankin, make these bizarre stars even more puzzling.

The scientists identified a pulsar that is able to dramatically change the way in which it shines. In just a few seconds, the star can quiet its radio waves while at the same time it makes its X-ray emissions much brighter.

The research “challenges all proposed pulsar emission theories,” the team writes in the Jan. 25 edition of the journal Science and reopens a decades-old debate about how these stars work.

Unexpected X-rays

Like the universe’s most powerful lighthouses, pulsars shine beams of radio waves and other radiation for trillions of miles. As these highly magnetized neutron stars rapidly rotate, a pair of beams sweeps by, appearing as flashes or pulses in telescopes on Earth.

Using a satellite X-ray telescope, coordinated with two radio telescopes on the ground, the team observed a pulsar that was previously known to flip on and off every few hours between strong (or “bright”) radio emissions and weak (or “quiet”) radio emissions.

Monitoring simultaneously in X-rays and radio waves, the team revealed that this pulsar exhibits the same behaviour, but in reverse, when observed at X-ray wavelengths.

This is the first time that a switching X-ray emission has been detected from a pulsar.

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