???? A new type of star gives clues to the mysterious origin of magnetars

2023-08-19 04:05:54

Magnetars are the most powerful magnets in the Universe. These super-dense dead stars, with an ultra-strong magnetic field, are found all over our galaxy, but astronomers don’t know exactly how they form.

Today, thanks to several telescopes around the world, including those of the European Southern Observatory (ESO), researchers have discovered an active star capable of becoming a magnetar (A magnetar is a neutron star with a magnetic field hyper-powerful, emitting…). This result marks the discovery of a new type of astronomical object – massive magnetic helium stars – and sheds light on the origin of magnetars.

Artist’s impression of HD 45166, the star that could become a magnetar – ESO

Although observed for over 100 years, the enigmatic nature of the star HD 45166 could not be easily explained by conventional models, and not much was known about it except that it is part of a pair of stars (1), that it is rich in helium and that it is more massive than our Sun.

“This star has become a bit of an obsession for me,” says Tomer Shenar, lead author of a study on this object published today in Science and Astronomer at University (A university is an institution of higher education whose purpose is is the…) of Amsterdam, the Netherlands. “Tomer and I call HD 45166 the ‘zombie star’,” says Julia Bodensteiner, ESO astronomer and co-author of the study. “It’s not just because this star is so unique, but also because I jokingly said it turned Tomer into a zombie.”

Having studied similar helium-rich stars before, Tomer Shenar thought magnetic fields might solve the problem. Indeed, magnetic fields are known to influence the behavior of stars and could explain why traditional models have failed to describe HD 45166, located about 3,000 light-years from Earth in the constellation Unicorn. “I remember having a click while reading the literature: What if the star was magnetic?”, says Tomer Shenar, who currently works at the Center for Astrobiology in Madrid, Spain.

Tomer Shenar and his team set out to study the star using several facilities around the world. The main observations were made in February 2022 using an instrument of the Canada-France-Hawaii Telescope capable of detecting and measuring magnetic fields. The team also relied on data from essential archives obtained with the FEROS (Fiber-fed Extended Range Optical Spectrograph) at ESO’s La Silla Observatory in Chile.

Once the observations were collected, Tomer Shenar asked his co-author Gregg Wade, a star magnetic field specialist at the Royal Military College of Canada, to examine the data. Gregg Wade’s response confirmed his hunch: “Well, dear friend, whatever that thing is, it sure is magnetic”.

Tomer Shenar’s team found that the star has an incredibly strong magnetic field of 43,000 gauss, making HD 45166 the most magnetic massive star discovered to date (2). “The entire surface of this helium star has a magnetic field about 100,000 times stronger than Earth’s,” says Pablo Marchant, an astronomer at the Institute. is…) of astronomy (Astronomy is the science of observing the stars, seeking to explain…) from the Catholic University of Louvain (KU Leuven) in Belgium, co-author of the study.

This observation marks the discovery of the very first massive magnetic helium star. “It is exciting to discover a new kind of astronomical object,” says Tomer Shenar, “especially when it has been hidden in plain sight for a long time.”

In addition, this object provides clues to the origin of magnetars, compact dead stars with magnetic fields at least a billion times stronger than that of HD 45166. The team’s calculations suggest that this star will end its life. in the form of a magnetar. By collapsing under the effect of its own gravity (Gravitation is one of the four fundamental interactions of physics.), its magnetic field will strengthen and the star will eventually become a very compact core with a magnetic field of about 100 trillion gauss (3) – the strongest type of magnet in the Universe.

Tomer Shenar and his team also found that HD 45166 has a smaller mass than previously reported, about twice the mass of the Sun, and that its stellar pair orbits at a far greater distance than previously thought. now. Furthermore, their research indicates that HD 45166 was formed by the merger of two small helium-rich stars. “Our results completely modify (Completion or completely automatic, or by Anglicism completion or…) our understanding of HD 45166”, concludes Julia Bodensteiner.

Notes:

(1) Although HD 45166 is a binary system, in this text HD 45166 refers to the helium-rich star, not the two stars.
(2) The 43,000 gauss magnetic field is the strongest ever detected in a star that exceeds the Chandrasekhar mass limit, which is the critical limit beyond which stars can collapse into neutron stars (the magnetars are a type of neutron star).
(3) In this text, a billion corresponds to a number followed by nine zeros and a trillion corresponds to a number followed by 12 zeros.

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