by The most extreme stars of the universe got a little more unexpected and mysterious.
Scientists were surprised when they saw a “dead” neutron star with one of the most powerful magnetic fields in the cosmos unexpectedly emerge. The reactivation of this neutron star or “magnet” does not conform to the current understanding of these exotic celestial objects.
The team discovered this magnetar return from the dead when they spotted strange radio signals from the nearest magnetar to Earth, XTE J1810-197, located about 8,000 light-years away, using the Commonwealth Scientific and Industrial Research Organization Australia (CSIRO). ) Parkes radio telescope, Murriyang.
Most magnets are known to emit polarized light, light with waves oriented in any particular direction. The team’s results show that this light is a circularly polarized magnet, appearing spirally as it moves through space. This is not only unexpected, it is also completely unprecedented.
Related: A ‘Vampire’ neutron star explosion linked to jets traveling at near-light speed
“Unlike the radio signals we’ve seen from other magnetars, this one is emitting massive amounts of rapidly changing circular polarization,” team leader and CSIRO scientist Marcus Lower said in a statement. “We’ve never seen anything like this before.”
XTE J1810-197 large even for a magnet
We’ve never seen anything like it before.”
Magnets, like all neutron stars, exist when massive stars die. When these stars exhaust their fuel for nuclear fusion of hydrogen to helium in their cores, the energy that supported them against the inward push of their own gravity is cut off.
As the tug-of-war between gravity and radiation pressure ends after millions of years, the outer layers of the star are ejected in a supernova explosion, causing the dying star to lose most of its mass. .
This leaves a stellar core with a mass of one to two times the mass of the Sun, which falls to a width of about 12 miles (20 kilometers), about the size of an average city on Earth. As a result, the material that makes up a neutron star is so dense that if one teaspoon of it were brought to Earth it would weigh 10 million tons.
The rapid collapse of the core causes the neutron star to greatly increase its rotation rate, just like an ice skater pulling in their arms to increase their spin but on a much larger scale. This means that some newly formed neutron stars can spin as fast as 700 times per second.
The collapse of this stellar core has another consequence. The magnetic field lines of the dying star are pushed together, causing the magnetic field to strengthen. As a result, some neutron stars have magnetic fields that are a quadrillion (1 followed by 15 zeros) times more powerful than the sun’s magnetic field. This qualifies these neutron stars for their own category, magnetars.
Radio wave pulses from magnetars are extremely rare, and XTE J1810-197 is just one of a handful of magnetars known to produce them. XTE J1810-197 was first seen emitting radio waves in 2003, but then this magnetar fell silent for more than a decade.
The magnetar was seen emitting radio waves again in 2018 at the University of Manchester’s 76-m Lovell telescope at the Jodrell Bank Observatory. This was followed by Murriyang, based in Wiradjuri Country, Australia, who has been observing XTE J1810-197 ever since.
Although this observation is completely unexpected, the team has an idea why this magnet could generate such unusual emissions.
“Our results indicate that there is a superheated plasma above the magnetic pole of the magnetar, which is acting like a polarization filter,” said Lower. “It remains to be determined how exactly the plasma is doing this.”
The 64-metre Murriyang telescope is outfitted with a pioneering ultra-wide bandwidth receiver, designed by CSIRO engineers, which is highly sensitive to changes in brightness and polarization over a wide range of radio frequencies. This helps to gather precise measurements of a range of celestial objects, particularly magnetars.
RELATED STORIES:
— A new approach could help scientists see inside a neutron star
— Dead star ‘glitches’ could reveal the origin of fast radio bursts
— The heaviest neutron star ever seen is shredding its companion
The researchers hope Murriyang’s continued observations of XTE J1810-197 will help provide insights into a range of large, powerful and unusual magnetar phenomena, such as plasma dynamics, X-ray and gamma-ray bursts, and their d could be fast. radio explodes.
The team’s research was published in the journal Nature Astronomy.
