Astronomers have discovered that rapidly spinning dead neutron stars at the heart of pulsars can emit radio signals from their edges. The finding could overturn decades of thinking that suggested pulsars only blast radiation from near their surface and at their poles.
Pulsarslike everyone else neutron starsthey are created when they are big stars run out of the fuel needed for their internal nuclear process and thus collapse, creating stellar remnants with dense matter that if a teaspoon of it can be brought to. The worldit would weigh about 10 million tons. This collapse also produces the strongest gravitational field in the universe – and, like the space-sized spacecraft in their hands to increase speed, the collapse can also accelerate the rotation of neutron stars up to 700 times per second.
The new research team analyzed nearly 200 radio observations of rapidly rotating pulsars, or millisecond pulsars, and compared them with data collected on gamma rays. This revealed radio waves coming from two or more regions around 33% of millisecond pulsars. Only 3% of slow-rotating neutron stars have been observed to emit radio waves outside of their cores.
Then the fact that the radio waves are more distant and consistent with gamma-ray bursts from these pulsars detected by NASA. Fermi Space Telescope demonstrated to the team that the two types of electromagnetic radiation come from the same non-polar and distant regions around these pulsars.
“As we see the signals of stars and from the edge of gravity, this study shows that these small rapidly rotating stars are more complex and strange than we thought,” said team member, Simon Johnston of the Australian science center CSIRO (Commonwealth Scientific and Industrial Research Organisation). said in a statement.
The team concluded that these data indicate that millisecond pulsars produce radio waves near the poles of these dead stars and the “current sheet” of charged particles – which are far from the neutron star and beyond its gravitational pull – which rotates with the motion of the dead star.
Current papers were already known to be responsible for the gamma-ray production of millisecond pulsars, therefore, the alignment between radio waves and gamma rays indicates a shared point of origin.
This may also explain why some millisecond pulsars have strange, broken radio signals. What astronomers see, whether it’s radio waves from the poles, from the current paper, or both, depends on how the pulsar is facing our telescopes.
One important result of this study and its findings is the fact that millisecond pulsars should be easier to detect than astronomers had previously thought. That’s because radio waves flow in different directions rather than traveling in a narrow cone from the poles. That means the pulsar doesn’t have to be in direct contact with Earth for its radio emissions to be observed.
While this is good news for projects such as measuring gravitational waves in space that use many types of pulsars, the team is still puzzled by how radio waves can be generated so far away from neutron stars and the turbulent fields they produce.
“Understanding where their signals come from – and why they look the way they do – is important for using them as accurate instruments,” team member Michael Kramer of the Max Planck Institute for Radio Astronomy (MPIfR), Germany, said in the statement.
The team’s results were published on March 25 in the newspaper Monthly Notices of the Royal Astronomical Society.
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