Magnetic Beast Ancestor: Star Researchers Uncover Peculiar New Class of Star

An artist’s depiction reveals an extraordinary star poised to turn into one of the cosmos’ most magnetic entities, a form of neutron star termed a magnetar. This observation introduces a previously unknown astronomical phenomenon — a massive magnetic helium star — and provides insight into magnetars’ genesis. In a matter of a few million years, HD 45166 will erupt into a brilliantly glowing, yet not incredibly forceful, supernova. Amid this blast, the core will shrink, enclosing and intensifying the star’s already intimidating magnetic fields. The aftermath will be a neutron star with a magnetic intensity vastly surpassing that of its ancestor. Credit: NOIRLab/AURA/NSF/P. Marenfeld/M. Zamani

Researchers pinpoint a distinctly rare star that could transform into the known Universe’s most magnetic entity, a magnetar.

Astronomers have detected an extraordinarily rare star that possesses the strongest magnetic force ever seen in a large star, with the potential to become one of the most magnetic things in the cosmos: a form of neutron star referred to as a magnetar. This revelation signifies the unearthing of an unprecedented class of celestial object — a substantial magnetic helium star — and provides clarity about the birth of magnetars.

Deciphering Neutron Stars and Magnetars

Neutron stars, the dense residues left after a massive star’s supernova explosion, are regarded as the densest substance in the cosmos. Some neutron stars, known as magnetars, also boast the most potent magnetic fields of any known object. The process through which these small, roughly 15 kilometers (9 miles) in diameter, objects develop such immense magnetic fields continues to baffle scientists.

An artist’s representation visualizes the final destiny of HD 45166 after its core collapses, leading to a neutron star with a magnetic force of around 100 trillion gauss — the Universe’s most formidable magnet. Credit: NOIRLab/AURA/NSF/P. Marenfeld/M. Zamani

Helium Stars and Magnetars: An Uncovered Connection

Recent findings by a group of star researchers, including NSF’s NOIRLab’s André-Nicolas Chené, might reveal vital information regarding the roots of these magnetic giants. Utilizing telescopes worldwide, like the Canada-France-Hawai‘i Telescope (CFHT) on Maunakea, the scientists have identified an unprecedented celestial entity — a hefty magnetic helium star. This rare version of a Wolf-Rayet star may be a magnetar’s forebearer.

Chené explained, “We’ve discovered a powerful magnetic field in a massive helium star for the first time. Our research indicates that this helium star will ultimately become a magnetar.”

HD 45166’s Enigmas

HD 45166, despite a century of examination by astronomers, has remained largely a mystery. Simple facts, like its helium-rich nature, slightly larger size compared to our Sun, and its binary system status, have been revealed.

An artist’s illustration describes how, in several million years, HD 45166 will detonate as a strikingly luminous, though not exceptionally energetic, supernova. During this cataclysm, its core will shrink, encasing and amplifying the star’s already fearsome magnetic fields. Credit: NOIRLab/AURA/NSF/P. Marenfeld/M. Zamani

Tomer Shenar, a University of Amsterdam astronomer, confessed, “I became somewhat fixated on this star.” Having examined analogous helium-rich stars previously, Shenar was fascinated by HD 45166’s atypical traits, displaying some Wolf-Rayet star features but with a unique spectral fingerprint. He hypothesized that magnetic forces could elucidate these mystifying characteristics. “I recall realizing, ‘What if the star is magnetic?’ while studying the literature,” he remarked.

Shenar, Chené, and their colleagues endeavored to validate this supposition by conducting fresh spectroscopic observations with the CFHT. The results revealed an extraordinary magnetic field of approximately 43,000 gauss, the most intense ever observed in a large star. Further analysis of its interaction with its partner star allowed accurate estimations of its mass and age.

NOIRLab astronomer André-Nicolas Chené explains how a distinctly uncommon star, harboring the mightiest magnetic force ever discovered in a large star, was uncovered — a star that might evolve into one of the Universe’s most magnetic objects. This discovery indicates a new celestial category’s identification — a significant magnetic helium star — and illuminates magnetars’ origin. Credit: NOIRLab/AURA/NSF/P. Marenfeld

Unlike other helium stars that evolve from a red supergiant, this specific star likely resulted from two intermediate-mass stars’ fusion.

Chené said, “This presents a highly particular scenario, leading us to wonder how many magnetars are birthed from similar systems and how many from other kinds of systems.”

HD 45166’s Future and the Origins of Magnetars

In the coming millions of years, HD 45166, situated 3000 light-years away in the Monoceros constellation (the Unicorn), will explode in a radiant yet not extraordinarily vigorous supernova. During this event, its core will shrink, enclosing and intensifying its already terrifying magnetic forces. The outcome will be a neutron star with a magnetic field reaching around 100 trillion gauss — the most powerful magnet in existence.

Chené noted, “We believed the likeliest magnetar candidates would emerge from the most massive stars. This research demonstrates that even less massive stars can lead to a magnetar, given the right circumstances.”

For additional information on this study, see Massive Magnetic Helium Stars: A Novel Class of Celestial Entity.

Reference: “A massive helium star with a magnetic field strong enough to form a magnetar” by Tomer Shenar et al., 17 August 2023, Science.
DOI: 10.1126/science.ade3293

Notes

The investigators also employed essential archived data obtained with the Fiber-fed Extended Range Optical Spectrograph (FEROS) at ESO’s La Silla Observatory in Chile.
Gauss is a metric for magnetic induction, essentially a gauge of magnetic power. The Sun’s normal polar magnetic field is 1–2 gauss, while sunspots can reach magnetic strengths of roughly 3000 gauss.

Frequently Asked Questions (FAQs) about magnetar

More about magnetar

• Massive Magnetic Helium Stars: A New Type of Astronomical Object
• Canada-France-Hawai‘i Telescope (CFHT)
• NOIRLab
• Magnetars – NASA’s Science Mission Directorate
• La Silla Observatory in Chile – ESO