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A Very “Extreme” Dead Star in the Universe has Suddenly Come Back to Life

The most extreme stars in the cosmos have just become even more startling and enigmatic.

When a “dead” neutron star with one of the strongest magnetic fields in the universe suddenly came back to life, scientists were shocked. Reactivating this highly magnetic neutron star, often known as a “magnetar,” defies current theories about these unusual astronomical objects.

Using the Australian Commonwealth Scientific and Industrial Research Organisation (CSIRO) Parkes radio telescope, Murriyang, the team detected unusual radio signals from the closest known magnetar to Earth, XTE J1810-197, which is situated approximately 8,000 light-years away. This led them to the discovery of this magnetar’s resurrection.

It is known that the majority of magnetars emit polarized light, or light with waves oriented in a specific direction. The light from this circularly polarized magnetar appears to spiral as it travels across space, according to the team’s results. Not only is this unexpected, but it’s never happened before.

Marcus Lower, a CSIRO scientist and team leader, said in a statement that”Unlike the radio signals we’ve seen from other magnetars, this one is emitting enormous amounts of rapidly changing circular polarization,” “We have never seen anything like this before.”

Significant Even for a Magnetar, XTE J1810-197

When massive stars die, magnetars—like all neutron stars—are produced. These stars lose the energy that has kept them from being pushed inward by their own gravity when the fuel for the nuclear fusion of hydrogen to helium in their cores runs out.

After millions of years, a supernova explosion propels the star’s outer layers outward, ending the tug-of-war between radiation pressure and gravity. As a result, the dying star loses almost all of its mass.

This leaves a stellar core that collapses to a width of around 12 miles (20 kilometers), or roughly the size of an average city on Earth, with a mass between one and two times that of the sun. Because of this, a teaspoon-sized amount of the mass that makes up a neutron star would weigh 10 million tons if it were brought to Earth.

Similar to an ice skater drawing in their arms to accelerate their spin on a far larger scale, the neutron star’s rapid core collapse likewise significantly increases its rate of rotation. This implies that the spin speed of some recently generated neutron stars can reach 700 Hz.

There is another effect of this star core collapsing. The magnetic field becomes stronger as a result of the dying star’s magnetic field lines being compressed together. Because of this, the magnetic fields of some neutron stars are a quadrillion (1 followed by 15 zeroes) times stronger than the magnetic field of the sun. Because of this, these neutron stars fall under the magnetars category.

Only a small number of known magnetars—including XTE J1810-197—have been found to emit radio wave pulses, making magnetar detection extremely unusual. After being observed to be producing radio waves for the first time in 2003, XTE J1810-197 became silent for more than ten years.

In 2018, the 76-meter Lovell telescope at Jodrell Bank Observatory, part of the University of Manchester, observed the magnetar generating radio waves once more. Following this, Murriyang, which is situated in Australia’s Wiradjuri Country, began observing XTE J1810-197.

The team has a theory as to why this magnetar would be producing such strange emissions, despite the fact that this observation is entirely unexpected.

“Our results suggest there is a superheated plasma above the magnetar’s magnetic pole, which is acting like a polarizing filter,” Lower explained. “How exactly the plasma is doing this is still to be determined.”

The state-of-the-art ultra-wide bandwidth receiver on the 64-meter telescope Murriyang was created by CSIRO engineers and is extremely sensitive to variations in brightness and polarization over a wide spectrum of radio frequencies. This aids in obtaining accurate measurements of a variety of astronomical objects, particularly magnetars.

With further studies of XTE J1810-197 using Murriyang, the researchers intend to shed light on a variety of extreme, potent, and uncommon phenomena connected to magnetars, including plasma dynamics, X-ray and gamma-ray bursts, and maybe rapid radio bursts.

The journal Nature Astronomy published the team’s research.

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