This star could become one of the strongest magnets in the universe

This artist’s impression shows a highly unusual star destined to become one of the most magnetic objects in the Universe: a variant of a neutron star known as a magnetar. It will explode as a supernova, the core will contract, and concentrate the star’s already daunting magnetic field lines to create the magnetar. Courtesy NOIRLAB

Imagine a star that is alive and has a magnetic field at least 100,000 times stronger than the one found on Earth. The peculiar stellar object HD 45166 is that. It has a staggering 43,000 Gauss field. As a result, it is a giant magnetic helium star, a brand-new class of object. It will turn into a “magnetar” sort of neutron star when it collapses in a million years, which will make it even odd.

Astronomer Tomer Shenar of the University of Amsterdam claims that HD 45166 offers hints about the origin of magnetars. He is the leader of a group examining this unusual thing. They have discovered that this item is not a typical huge star. Instead, they believe it to be the remnants of two lower-mass helium stars merging.

“Some of their mass was lost during the merging process,” he wrote in an email. The end outcome is a highly magnetized helium star that resembles the core of a star that was once eight times as big as the Sun and was therefore massive enough to explode as a supernova and collapse into a neutron star.

 

A highly evolved Wolf-Rayet star is the freshly produced helium object. There are still certain modifications that must be made before it can become a magnetar. Models of the development of the star predict that it will eventually erupt as a supernova of class Ib or IIb. The already powerful magnetic field will intensify as it disintegrates under the weight of itself. The object will eventually collapse into a very small core with a magnetic field of approximately 100 trillion Gauss. That would make it a magnetar, one of the strongest sorts of magnets known to exist.

Studying the Progenitor for Clues

The Wolf-Rayet star is one of a stellar pair that makes up HD 45166. Over a century of observation by astronomers failed to explain its peculiar properties. Shenar and her study partner Julia Bodensteiner (of Katholieke Universiteit in the Netherlands) made the decision to investigate the peculiarities of it in greater detail. Shenar, who has investigated other helium-rich stars, admitted that “this star kind of became an obsession of mine.” He started to consider whether the knowledge he and others had about this object might be explained by a powerful magnetic field.

In all of the universe’s events and things, magnetic fields are significant. They undoubtedly have an impact on behavior all throughout a star’s life. Therefore, when faced with a celestial enigma, it is not strange to take magnetic fields into consideration. Shenar recalled, “I remember having a Eureka moment while reading the literature: ‘What if the star is magnetic?'”

Shenar and his colleagues requested and obtained time on many telescopes to investigate that theory and determine whether this object is a proto-magnetar. The bulk of the observations took place in February 2022. The researchers made use of a magnetic field detection and measurement tool on the Canada-France-Hawaii Telescope. The Fiber-fed Extended Range Optical Spectrograph (FEROS) at the ESO La Silla Observatory in Chile’s archives was also used by the researchers.

The astronomers discovered the star had a 43 kiloGauss magnetic field strength in this way. The helium star’s entire surface has a magnetic field that is over 100,000 times stronger than Earth’s, according to team member Pablo Marchant, an astronomer at the Institute of Astronomy at the KU Leuven in Belgium.

With this observation, the first big magnetic helium star has been found. Finding a new class of celestial object is exciting, adds Shenar, “especially when it has been hiding in plain sight the entire time.”

How Do Magnetars Form?

Another intriguing hint regarding the origins of magnetars comes from the discovery of HD 45166’s peculiar origins. These things are really peculiar inhabitants of the cosmic zoo. Neutron stars that remain hot after supermassive stars die are known as magnetars. In essence, neutron stars are the remnants of enormous stars that once burned with life. They are no longer stars with active nuclear fusion inside of them. In its place, these monsters are spinning spheres of concentrated neutrons that are closely clustered. Gravity is quite powerful because to all that mass. A magnetic field that is trillions of times stronger than Earth’s is also being produced from within by something.

 

The magnetic fields produced by magnetars are stronger than those of their progenitor neutron stars by at least a thousand times. The process most likely results from conducting “fluids” in the star going through a magnetohydrodynamic process. This essentially parallels what transpires in the roiling planet’s core. Magnetars are thought to have solid, crusty surfaces, just like their neutron star ancestors.

The origins of these objects’ powerful magnetic fields are still being studied by astronomers. They pondered the notion that such strong fields might be enabled by star mergers as long back as 2009. Shenar asserts that the proto-magnetar creation process is likely where HD 45166’s magnetic field originated. The strong magnetic field that resulted from it “got frozen” within the layers of the star, according to him. The future magnetar will distinguish itself by having that field.

The Milky Way Galaxy contains at least 29 known magnetars, which are detectable by us thanks to their X-ray and gamma-ray emissions. The emissions eventually halt as the magnetic fields loosen and diminish. A lifeless core is left behind. There are probably millions of dormant magnetars in our galaxy.