New observation breaks long-standing belief about neutron stars

Scientists have refuted a widely accepted idea about neutron stars with a recent observation of a high-energy particle jet.

We have recently written a lot about relativistic jets: they are particles that come out of black holes or neutron stars at a speed close to light. But scientists have long thought that strong magnetic fields around certain neutron stars would prevent the formation of jets. This new observation would break this idea – it comes back to the drawing board, again.

"We have refuted the old idea, and now we do not know the new thing," the study's author, Jakob van den Eijnden, astronomer of the University of Amsterdam, told Gizmodo. "This is how science progresses and knowledge emerges".

Scientists have observed neutron stars, dense objects that are heavier than the sun but not larger than New York, rotating by emitting light radiation or projecting jets of particles. But the records of the 1970s and 1980s, as well as more recent observations, did not reveal any jet particles from neutron stars with strong magnetic fields, a hundred thousand times more powerful than the intense magnetic fields produced in the laboratories. of physics. Thus, based on all these observations, the researchers guessed that these neutron stars simply could not produce jets, and they excluded highly magnetized neutron stars from theories of jet formation.

But the most recent discovery changes that. On October 3, 2017, the Swift X-ray Observatory detected a burst of X-rays and attributed it to a neutron star called Swift J0243.6 + 6124 that was spinning every 10 seconds or so, which is slow enough for a neutron star. magnetic field. X-rays indicated that the star was surrounded by a disc of matter, perhaps sucked by a close companion. They continued with eight observations from October 2017 to January 2018 using the Very Large Array, an American radio telescope. The observation of radio observations over time and the correspondence between the behavior of light and X-rays indicated to astronomers that the neutron star also emitted a jet.

It was a chance observation, explained van den Eijnden. They were observing other sources that, once again, did not provide enough information to indicate the presence of a jet when this new source appeared. "I remember getting the first radio detection that told us we had seen a jet and we were very excited," he said.

Before this discovery, theorists thought that jets formed by magnetic activity at the inner part of the disc of matter surrounding the neutron star, but that a stronger field would stifle the process and would prevent a jet to form. So what's going on here? According to the article published in Nature, the jet may originate from the outside of the disc where the magnetic field is weaker.

Or maybe spinning the neutron star feeds the jet. Astronomer Nathalie Degenaar, of the University of Amsterdam, said that if the rotation fed the jet, the slower-moving neutron stars would have a smaller jet, as is the case here, according to a press release. press.

Bettina Posselt, a Penn State astronomer who studies different aspects of neutron stars and did not participate in the new study, told Gizmodo that the document was interesting. Her findings have implications for the theories about the form of these relativistic jets, she said.

So, again, a new discovery has obscured scientists' understanding of these wild cosmic objects, and it is time for new theories to emerge.

"In science, when you try to answer questions, you do not get an answer – you get more questions," van den Eijnden said. "This is the case here."