Astronomers Discover Missing Link Between X-ray and Radio Pulsars [VIDEO]

After decades of searching, astronomers have discovered a star that, in a manner reminiscent of Jekyll and Hyde, alternates between two identifies -- that of emitting X-rays on the one hand, and radio on the other. The discovery, according to those behind it, marks an intermediate phase in the life of pulsars, or rapidly spinning neutron stars.

"This transitional object took us decades to find, and it provides us with a unique opportunity to observe a pulsar's intense magnetic field in action," said Sergio Campana, an astronomer at Brera Observatory in Merate, Italy, and a co-author of a paper published in the journal Nature.

Neutron stars represent the closest thing to a black hole that can be observed directly: created in the cores of massive stars during supernova explosions, neutron stars are so dense that a teaspoonful of one can weigh as much as a mountain. A pulsar, meanwhile, is a magnetized neutron star that regularly emits pulses of light.

In the case of millisecond pulsars, like the one at the center of the new discovery, extremely high levels of density and powerful magnetic fields are combined with rapid rotations.

The switch between X-rays and radio is triggered by the rise and fall of gas streaming onto the pulsar from a companion stars. During the course of a pulsar's life, gas flows from the companion star onto the neutron star where it is heated to millions of degrees, creating X-rays in the process.

Eventually, the neutron star is completely coated in gas, which, upon reaching a certain depth, yields a runaway thermonuclear reaction and explodes in a burst of X-rays.

After roughly a billion years, the gas flow from the normal star tapers off, putting an end to X-ray pulses. The star's spin and magnetic field together keep the star pulsing, however, only this time radio waves are emitted.

In the case of the new discovery, earlier this year researchers observed a flash of X-rays from a previously unknown source. Located in the core of a globular star roughly 18,000 light-years away, the researchers were able to identify the source of the emissions using the Swift X-ray Telescope (XRT).

A week later, a team from Spain used the XMM-Newton satellite to locate the object, at which point they detected X-ray pulses that indicated the neutron star was spinning every 3.0 milliseconds and was joined by a small companion star less than one-fifth the mass of the Sun.

However, later observations revealed alterations between X-ray and radio emissions, leaving the astronomers with a situation they had never encountered before.

According to Alessandro Papitto of the Institute of Space Sciences in Spain, the unique behavior is likely the result of the interaction between the pulsar's magnetic field and variations in the gas flow from the companion. For example, when the mass flow is lower, the magnetic field sweeps the gas away, preventing it from reaching the surface and emitting X-rays.

"At high mass flow rates, the gas squeezes the magnetic field and is able to reach the surface to produce X-ray emission. At the same time, the dense cloud of ionized gas surrounding the pulsar quenches the radio signals, effectively blocking them from our view," Papitto explained.

Once thought to occur on the scale of millions of years, the new study shows that these multiple personality stars can change, literally, overnight.