One of the stranger objects in the Universe just got a bit stranger as researchers have found a pulsar that switches between emitting X-rays and radio waves. It has been predicted that pulsars switch like this over the course of millions of years, as they age, but not back and forth over weeks. This discovery was made by an international team of scientists using multiple space telescopes, including NASA's Swift and Chandra satellites, and ESA's XMM-Newton.
Pulsars are a special class of neutron stars, which are formed when large enough stars go supernova. The force of the implosion crushes atoms to the point that electrons and protons collide, leaving a giant mass of neutrons behind. If a neutron star is spinning fast enough, its magnetic fields will restrict where light is emitted to its poles, and if the poles cross over Earth, we will see the light pulsing on and off. When the pulsar has another star nearby to feed from, gas will collect around it and on its surface. As the gas falls in, it will produce X-rays, but also when enough of it collects on the pulsars surface, it will trigger a thermonuclear explosion to produce a burst of X-rays. It was one of these bursts that first caught the researchers' attention. Upon further examination, the X-rays stopped, and radio waves were being detected, which indicates the gas was no longer falling onto the pulsar. Two days later though, the X-rays unexpectedly started up again.
The researchers hypothesize that what is happening is the magnetic field of the pulsar pushes away the gas being pulled in from the companion star, which enables its naturally emitted radio waves to escape. Eventually there too much mass to be swept away though, so the gas starts producing X-rays again, and blocks the radio waves.