New type of star gives clues to mysterious origin of magnetars

The finding marks the discovery of a new type of astronomical object – massive magnetic helium stars.

An artist’s impression of the star HD 45166 located in the constellation Monoceros (L Calcada/ESO/PA)

A new type of star is shedding light on the mysterious origin of magnetars – the strongest magnets in the universe.

Magnetars are super-dense dead stars with ultra-strong magnetic fields, and can be found all over the Milky Way.

Although astronomers do not know exactly how they form, using multiple telescopes around the world, including European Southern Observatory (ESO) facilities, researchers have uncovered a living star that is likely to become a magnetar.

The finding marks the discovery of a new type of astronomical object – massive magnetic helium stars – and sheds light on the origin of magnetars.

It is exciting to uncover a new type of astronomical object, especially when it’s been hiding in plain sight all along

Tomer Shenar, University of Amsterdam

The enigmatic nature of the star HD 45166 could not be easily explained by conventional models, even though it had been observed for more than 100 years.

Little was known about it beyond the fact that it is one of a pair of stars, is rich in helium and is a few times more massive than the Sun.

Lead author, Tomer Shenar, an astronomer at the University of Amsterdam in the Netherlands, said the star had become a “bit of an obsession”.

Co-author and ESO astronomer Julia Bodensteiner, based in Germany, said: “Tomer and I refer to HD 45166 as the ‘zombie star’.

“This is not only because this star is so unique, but also because I jokingly said that it turns Tomer into a zombie.”

Magnetic fields are known to influence the behaviour of stars and could explain why traditional models failed to describe HD 45166, which is located about 3,000 light-years away in the constellation Monoceros.

According to the study, the star has an incredibly strong magnetic field, and is one of the most magnetic massive stars found to date.

“The entire surface of the helium star is as magnetic as the strongest human-made magnets,” said co-author Pablo Marchant, an astronomer at KU Leuven’s Institute of Astronomy in Belgium.

The scientists suggest the observation marks the discovery of the very first massive magnetic helium star.

Dr Shenar said: “It is exciting to uncover a new type of astronomical object, especially when it’s been hiding in plain sight all along.”

The findings, published in the Science journal, provide clues to the origin of magnetars, compact dead stars laced with magnetic fields at least a billion times stronger than the one in HD 45166.

The team’s calculations suggest this star will end its life as a magnetar.

As it collapses under its own gravity, its magnetic field will strengthen, and the star will eventually become a very compact core, and the most powerful type of magnet in the universe.