Astronomers today announced that they have found a “missing link” for pulsar research. A pulsar has been found to oscillate between emitting radio waves and X-rays while spinning extremely fast.

Pulsars, which are the remnants of dead stars (neutron stars) that were not massive enough to become black holes, are generally classified by the type of electromagnetic emissions they create. As the super-dense objects spin, the throw out radiation such as radio waves an X-rays. Astronomers believe that neutron stars in binary star systems may be “spun up” as they take in matter from a companion star, then begin emitting X-rays as they spin more quickly.

The newly-discovered pulsar is referred to as a “millisecond pulsar” by astronomers, spitting out pulses of radiation in just milliseconds. It also represents a pulsar in the relatively short-lived in-between state of switching between emitting radio waves and X-rays as it accretes surrounding material. Observations of the pulsar are set to be published this week in the journal Nature.

“The search is finally over: with our discovery of a millisecond pulsar that, within only a few weeks, switched from being accretion-powered and X-ray-bright to rotation-powered and bright in radio waves, we finally have the missing link in pulsar evolution,” said Alessandro Papitto, an astronomer at the Institute of Space Sciences and lead author on the paper.

The pulsar, currently named IGR J18245-2452, was spotted emitting X-ray pulsed earlier this year using two European Space Agency (ESA) space telescopes. However, later observations revealed that the pulsar is actually the same one that was discovered by astronomers in 2006 – when it was observed emitting radio pulses. Further observations showed that the pulsar switched again to radio pulses just weeks after its “re-discovery.”

“At that time, it appeared to be just another millisecond radio pulsar, but now here it was shining in X-rays – this is clearly no ordinary pulsar,” said Papitto.

The new observations help confirm current theories about the formation of pulsars and millisecond pulsars in particular. They also shed light on how binary systems might evolve through time.

(Image courtesy ESA)