An unexpected discovery by an international group of scientists disproves existing theories about how astrophysical jets are ejected from neutron stars.
The group, which includes University of Alberta astronomer Gregory Sivakoff, found that as highly magnetic neutron stars accrete, or grow by consuming material in space, they emit jets—a discovery they never thought was possible.
When objects such as neutron stars and black holes accrete, some of it is released in outflows called jets.
“These are well-focused outflows of material that often travel at speeds near that of light,” said Sivakoff, co-author and associate professor in the Department of Physics.
Scientists have known about jets for more than 50 years, but little is understood about the physics of how these jets are launched, Sivakoff noted.
The researchers observed a highly magnetic neutron star named Swift J0243 by using the Very Large Array radio telescope at the National Radio Astronomy Observatory in New Mexico and NASA’s orbiting Neil Gehrels Swift Observatory.
“The radio spectrum of Swift J0243 is the same as that of jets from other sources and evolves in the same way,” said Jakob van den Eijnden, a PhD student from the University of Amsterdam who was the lead author of the study about the research. “The radio brightness also follows that of the in-falling gas, as seen in other jet-creating systems. So for the first time ever, we have observed a jet from a neutron star with a strong magnetic field.”
Until now, scientists believed it would be impossible for jets to form in highly magnetic neutron stars because their strong magnetic fields were thought to prevent the material from reaching the neutron star.
“This paper is important because it shows the first clear observation of a highly magnetic neutron star that is accreting and launching a jet,” added Sivakoff. “This means that we understand less than we thought we did when it comes to jets.”
Building an understanding of jets is important because they deposit large amounts of matter and energy into surrounding space. This can have a major impact on the immediate environment and may affect how entire galaxies form.
“Our goal is to study more highly magnetized neutron stars in the future to find out if the system we observed in this paper is typical or atypical of highly magnetized neutron star systems,” said Sivakoff.
The study, “An Evolving Jet From a Strongly Magnetized Accreting X-ray Pulsar,” was published in Nature.
Source: University of Alberta