NASA Fermi Spots a 'Transformer' Pulsar Changing Forms (VIDEO)

NASA's Fermi has spotted an unusual event. It watched as in late June 2013, a binary system containing a rapidly spinning neutron star underwent a startling change. The pulsar's radio beacon simply vanished while at the same time the system brightened fivefold in gamma rays.

A binary system consists of two stars that orbit around their common center of mass. This particular system is called AY Sextantis, and is located about 4,400 light-years away from Earth in the constellation Sextans. It's made up of a 1.7-millisecond pulsar and a star containing about one-fifth the mass of the sun. While young pulsars often appear in isolation, millisecond pulsars often appear in binary systems, which suggests an explanation for their rapid spin.

"Astronomers have long suspected millisecond pulsars were spun up through the transfer and accumulation of matter from their companion stars, so we often refer to them as recycled pulsars," said Anne Archibald, one of the researchers, in a news release.

In this system, the stars are close enough that a stream of gas flows from the sun-like star toward the pulsar. The pulsar's rapid rotation and magnetic field are responsible for both a radio beam and a powerful pulsar wind. But what caused the radio beam to disappear? Astronomers believe they may have the answer.

When the radio beam is detectable, the pulsar wind holds back the companion's gas stream surges, pushing its way closer to the pulsar and creating an accretion disk. The gas in this disk becomes compressed and heated enough to emit X-rays, and the material along the inner edge of the disk quickly loses orbital energy and descends around the pulsar. This obscures the radio beam.

The findings represent the first example of a transient, compact, low-mass gamma-ray binary. In the future, this system could serve as a natural "laboratory" to show scientists how millisecond pulsars form.

The findings are published in The Astrophysical Journal.

Want to learn more? Check out the video below, courtesy of YouTube.