Astronomers are used to seeing neutron stars suddenly increase their rate of spin, but they recently witnessed one suddenly slowing down.
Neutron stars are the result of a massive star running out of fuel, going supernova and collapsing into itself. Matter inside a neutron star is so dense that a teaspoonful would weigh about a billion tons on Earth.
Neutron stars can spin at up to 43,000 times per minute and have super strong magnetic fields -- up to a trillion times stronger than Earth’s.
The neutron star known among astronomers as 1E 2259+586 is where the slowdown in spinning was observed. It’s a type of neutron star known as a magnetar and is located about 10,000 light-years away from Earth in the constellation Cassiopeia.
Measurements of the star’s rotation taken from July 2011 to mid-April 2012 indicated the rotation “was gradually slowing from once every seven seconds, or about eight revolutions per minute. On April 28, 2012, data showed the spin rate had decreased abruptly, by 2.2 millionths of a second, and the magnetar was spinning down at a faster rate,” according to a NASA statement
"Astronomers have witnessed hundreds of events, called glitches, associated with sudden increases in the spin of neutron stars, but this sudden spin-down caught us off guard," said Victoria Kaspi, a professor of physics at McGill University in Montreal.
The slowdown has been termed an “anti-glitch.”
A week prior to noticing the slowdown, 1E 2259+586 produced a brief, but intense X-ray burst detected by the Gamma-ray Burst Monitor aboard NASA's Fermi Gamma-ray Space Telescope. The scientists think this 36-millisecond eruption of high-energy light likely signaled the changes that drove the magnetar's slowdown.
"What is really remarkable about this event is the combination of the magnetar's abrupt slowdown, the X-ray outburst, and the fact we now observe the star spinning down at a faster rate than before," said lead author Robert Archibald, a graduate student at McGill.
Scientists say the finding could reveal more about the internal structure of neutron stars, which has long been a mystery.