700 times per second! Pulsars outside the Milky Way are beyond people's imagination

There is a mystery outside the Milky Way! Where do radio bursts come from? Neutron stars or magnetars?

New research finds a close connection between neutron stars and fast radio bursts.

As shown in this picture, an extreme dead star (or magnetar) is producing fast radio bursts. (Image source: NASA)

Neutron stars are formed when massive stars die, and the new study reveals similar motions between different types of neutron stars. This may sound like a small discovery, but from a macroscopic perspective, this discovery further supports the idea that extremely dead stars, which are extremely dense, can be understood as small as a spoon and heavy as a mountain, and these extremely dead stars may be the cause of fast radio bursts.

Fast radio bursts, which last only milliseconds and appear to come from outside the Milky Way, have remained shrouded in mystery since they were discovered in 2007. However, there is now a preliminary conclusion: FRBs may originate from highly magnetized neutron stars or magnetars.

The new discovery, made by a team including researchers from the Max Planck Institute for Radio Astronomy and the University of Manchester, found that magnetars are indeed linked to other so-called "radio-strong" neutron stars in terms of their pulse structure and rotation.

The discovery of similar "universal scales" between different types of neutron stars suggests that plasma processes may be responsible for these bursts; the team also said that this leads scientists to interpret the structures seen in fast radio bursts as the result of corresponding rotation periods.

"When we started comparing the radiation from magnetars with that from fast radio bursts, we expected to find similarities, but we didn't expect this to be universal for all 'radio-strong' neutron stars," Michael Kramer, lead author of the paper and director of the Max Planck Institute for Radio Astronomy, said in a statement.

Neutron stars! Pulsars! Magnetars! It's incredible!

Neutron stars form when massive stars run out of fuel for nuclear fusion. When a star runs out of fuel, the energy that holds them against the inward pressure of their own gravity is gone. This then causes the outer layers of the star to be blown away, which in turn leads to a massive supernova explosion, while the core itself collapses.

This collapse will continue until the electrons and protons in the region collide with each other, creating a sea of ​​neutron-rich matter that prevents the core of the star from collapsing further. If further collapse occurs on this basis, the core will eventually form a black hole. The result of the core collapse process is an object roughly the width of an Earth city, about 12 miles (20 kilometers) wide, with an incredibly dense mass.

However, this is not the only extreme property that causes gravitational collapse. Just as a person would tighten their arms to spin faster while ice skating, the core of the star that creates a neutron star spins faster by reducing its radius. This spin acceleration process can have a considerable effect on the core. For example, some younger neutron stars can spin up to 700 times per second. If they send jets of radiation toward Earth, such rapidly spinning neutron stars are called pulsars, and the whole process is like a lighthouse beaming out beams in the universe. Neutron stars that spin hundreds of times per second are called millisecond pulsars.

While pulsars are known for their periodic properties, ASTRS are neutron stars that emit radio waves in a more sporadic and less regular pattern.

Furthermore, during this collapse, the magnetic field lines in the core of the star "collapse," forming a magnetic field that is 100 billion times stronger than Earth's. But some neutron stars have magnetic fields that are even stronger than normal neutron stars, more than a thousand times stronger. These are called magnetars.

Currently, astronomers know of about thirty magnetars, of which about six have been found to emit radio waves. From this, scientists speculate that fast radio bursts may come from magnetars outside the Milky Way - extragalactic magnetars.

Finding the connection between all the "radio-intense" neutron stars

The team investigated the connection between magnetars and fast radio bursts by studying in detail the individual pulses of six known magnetars. The Bad Münstereifel radio telescope in Germany, one of the largest omnidirectional radio telescopes on Earth, was used to detect the substructure of the pulses.

To the team's surprise, rapidly spinning millisecond pulsars and autotransformation transient radio sources had similar pulse structures. This led them to conclude that there is a universal scaling relationship between the pulse structure and the rotation period among magnetars and other forms of neutron stars, regardless of whether these extreme stars rotate every a few milliseconds or once every 100 seconds or so.

"We expect magnetars to get their energy from the energy of their magnetic fields, while other neutron stars get their energy from their rotational energy," Kuo Liu, a scientist at the Max Planck Institute for Radio Astronomy, said in the statement. "Some are very old, some are very young, but it seems that all neutron stars follow this rule."

In other words, all of these radio-emitting neutron stars behave like magnetars, suggesting that the intrinsic origin of these radio waves is the same for any neutron star that emits radio waves.

"If at least some FRBs originate from magnetars, then the timescale of the substructure in the bursts could tell us about the rotation period of the underlying magnetar source. If we find this periodicity in the data, it would be a milestone in interpreting this class of FRBs as radio sources," Ben Sappers, a researcher at the Jochol Bank Center for Astrophysics, said in the statement.

The team's research was published in the journal Nature Astronomy on November 23, 2023.

BY:Robert Lea

FY: Continent

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