Most Magnetic Large Star Ever Found Has 4000 Times Stronger Field than Our Sun

Shenar’s astronomy research team used an instrument on the Canada-France-Hawaii Telescope to look for the chemical fingerprints that magnetic fields can leave on a star’s spectrum and found HD45166 has a field strength of 43,000 Gauss. “One-thousand-Gauss magnetic fields are pretty rare amongst massive stars, so 43,000 Gauss is really off the chart,” says Paul Crowther (University of Sheffield, UK), who was not involved in the study. The large scale solar magnetic field near the poles of our Sun is basically dipolar with a strength of about 10 Gauss.

Analyzing HD45166 star’s brightness and motion, they determined that it had a companion star and was 2 times the mass of the sun and not 4 times. They also concluded that HD45166 came from the merger of two smaller stars.

Eventually, Shenar and his colleagues estimate that this star will collapse into a neutron star, and its magnetic field will strengthen as it does so. They think this will create a magnetar.

The cinders of burnt-out massive stars known as neutron stars have magnetic fields 1 trillion times stronger than the Sun’s. As the massive star collapses, its magnetic field lines are packed into a much tighter space, and the field strength increases. But then there are magnetars: These neutron stars have fields 1,000 times stronger again than regular neutron star.

HD45166 seems like the the kind of star that exists before it collapses into a magnetar.

HD 45166 is only 3,300 light-years away. Our Milky Way Galaxy likely contains thousands more. We know how they look like.

Journal Science – A massive helium star with a sufficiently strong magnetic field to form a magnetar

Editor’s summary

Magnetars are neutron stars with extremely strong magnetic fields, the origin of which is debated. One possibility is amplification of a magnetic field in the core of the parent star, which produces the neutron star during a supernova explosion. However, such fields have not been observed in stars that are about to explode. Shenar et al. used spectropolarimetry to identify a high magnetic field in a Wolf-Rayet, the exposed helium core of a star that has lost its outer layers of hydrogen. The mass of the Wolf-Rayet is high enough that it will produce a neutron star in a supernova, and the field is sufficiently strong to generate a magnetar during core collapse. —Keith T. Smith

Abstract

Magnetars are highly magnetized neutron stars, the formation mechanism of which is unknown. Hot helium-rich stars with spectra dominated by emission lines are known as Wolf-Rayet stars. We observed the binary system HD 45166 using spectropolarimetry and reanalyzed its orbit using archival data. We found that the system contains a Wolf-Rayet star with a mass of 2 solar masses and a magnetic field of 43 kilogauss. Stellar evolution calculations indicate that this component will explode as a supernova, and that its magnetic field is strong enough for the supernova to leave a magnetar remnant. We propose that the magnetized Wolf-Rayet star formed by the merger of two lower-mass helium stars.