A pulsar – a dead star not much larger than a city – has been spotted releasing a giant beam of particles and antiparticles about 7 light-years long, roughly 68 trillion kilometers (42 trillion miles). The filament of material was first discovered in 2020 using NASA’s Chandra X-ray observatory but it's only now its true extent is known.
In a paper accepted for publication in The Astrophysical Journal, Martijn de Vries and Roger Romani of Standford Univerity describe how the beam is rich in positrons, the antimatter equivalent of electrons. Pulsar PSR J2030+4415, like all neutron stars, is around 16 kilometers (10 miles) in diameter and yet thanks to its powerful magnetic field it can create a large beam of particles.
"It's amazing that a pulsar that's only 10 miles across can create a structure so big that we can see it from thousands of light-years away," lead author de Vries said in a statement. "With the same relative size, if the filament stretched from New York to Los Angeles the pulsar would be about 100 times smaller than the tiniest object visible to the naked eye."
Pulsars are incredible objects. When stars of a certain size go supernova, their core collapses down into a neutron star, an object of staggering density. A teaspoon of neutron star material weighs billions of tons, more than a mountain. And if these neutron stars rotate rapidly and pulsate they are known as pulsars.
Pulsars' extreme magnetic fields can accelerate particles to high-speed and they also produce high-energy radiation, which can create pairs of electrons and positrons. This is down to Einstein’s famous equation E = mc2. Energy can turn into matter and vice versa. So if matter and antimatter touch they annihilate and turn into pure energy. Equivalently, releases of high energy can create matter and antimatter particles.
Usually, the strong magnetic fields of the pulsar keep those particles confined, but here they are escaping. The researchers believe that this is due to how the pulsar was moving at high speed across the interstellar medium. This created a bow shock of charged particles. Over the last few decades, the pulsar caught up to the bow shock, as the latter slowed down, and the magnetic field of the pulsar aligned with the one from the interstellar medium.
"This likely triggered a particle leak," added Romani. "The pulsar wind's magnetic field linked up with the interstellar magnetic field, and the high-energy electrons and positrons squirted out through a nozzle formed by connection."
The release of particles continues to be energetic enough that they emit X-rays in their accelerated motions, which were spotted by Chandra. Events such as this might be the origin of cosmic antimatter.