One of the most interesting stars in the Milky Way still causes significant intrigue. In October 2020, the magnetar SGR 1935+2154, responsible for emitting never-before-detected radio signals in our galaxy, unexpectedly slowed down. Scientists now believe that the slowing of the spin may be evidence of a volcanic eruption on the star’s surface that spews material into space that alters the circumference of the star enough to slow the planet’s spin slightly.

This is a finding that may shed light on the mystery of fast radio bursts – how these super-dense dead stars can emit powerful radio bursts intermittently over millions of light-years.

“People think that neutron stars may be equivalent to volcanoes on their surface,” says astrophysicist Matthew Bering of Rice University in Houston, Texas. “Our findings suggest that this may be the case, in which case the refraction most likely occurs at or near the star’s magnetic pole.”

SGR 1935+2154 hit the scene – literally – in May 2020 when astronomers discovered it was emitting a short but powerful radio burst.

The reason this is exciting is because we’ve only detected such flares in other galaxies before. These explosions, which occur in the form of radio waves, last only milliseconds and emit as much energy as 500 million suns during this time. And most of them unexpectedly flared up once and have not been detected since.

Because of the remoteness and unpredictability of these fast radio bursts, it is very difficult to learn more. Astronomers were able to track down some galaxies that emitted them, but determining the mechanism or mechanisms behind them was much more difficult.

SGR 1935+2154 was a breakthrough: here we were finally able to follow a fast radio burst to a specific object. SGR 1935+2154 is a type of neutron star known as a magnetar.

Neutron stars are already at their extreme: the superdense cores of massive stars that become supernovae explode from the outer material, while the rest of the star’s heart collapses under the influence of gravity into a sphere that is about 2.4 times the mass of the Sun and about 20 times the mass of the Sun. kilometers (12 miles) in diameter. Add an insanely strong magnetic field that’s about 1,000 times stronger than a normal neutron star and a quadrillion times stronger than Earth’s, and you’ve got a magnetar.

Astronomers hypothesized that the outward pull of this magnetic field against the internal pressure of gravity could cause the magnetar to sometimes break apart, causing flashes and fast radio bursts. However, more information was needed, so SGR 1935+2154 remained under close observation. It was then caught emitting millisecond radio signals again in October 2020.

And now a research team led by George Washington University astrophysicist George Younes has discovered that just days before this activity, it did something really strange: It suddenly slowed down. Sometimes neutron stars suddenly change their rotational speed. This is called a glitch and is an under-studied phenomenon.

A neutron star glitch is usually a sudden acceleration in rotation speed. Slowing, sometimes known as anti-glitch, is much less common. Only three antiglucas were detected, including SGR 1935+2154. And while the glitch can be explained by changes inside the star, failure prevention cannot. So the researchers set out to investigate what might be causing it and what role the anti-glitch, if any, could play in creating the radio burst activity that was detected a few days later.

If internal changes couldn’t be the cause of the slowdown, the researchers turned to external explanations. Assuming that the rarity of both events—antigluck and radioactivity—means their temporal proximity comes to mind, they constructed a model based on a volcanic rupture in the magnetar’s surface that hurled a wind of particles into the space around the star. relationship.

“What makes the October 2020 event unique is that there is fast radio emission from the magnetar just days after the anti-glitch, and pulsed transient radio emission is turned on soon after,” says Behring.

“We’ve only seen a few transient pulsed radiomagnets, and this is the first time we’ve seen a magnetar radio switch operating almost simultaneously with an antigluck.”

And according to their model, a break near the star’s pole could create a wind that interacts with the magnetar’s magnetic field, slowing the star’s spin rate and changing the geometry of the magnetic field, improving radio emission conditions. The team found that strong winds blowing from a volcano-like region for just a few hours can create the conditions for slowing down and more radioactivity.

“Interpreting wind opens the way to understanding why radio emission is on,” says Behring.

“It provides a new understanding that we didn’t have before.”