Stars found to have ‘super strong’ magnetic fields

In a surprising discovery, astronomers have detected strong magnetic fields in stars twice the size of our Sun.

The international team led by astrophysicist Dennis Stello, from the University of Sydney, detected stars with internal magnetic fields 10 million times stronger than Earth’s.

Dr Stello said: “This is tremendously exciting, and totally unexpected. Because only five to 10 percent of stars were previously thought to host strong magnetic fields, current models of how stars evolve lack magnetic fields as a fundamental ingredient.  Such fields have simply been regarded insignificant for our general understanding of stellar evolution.”

The scientists observed stellar oscillations – sound waves from the stars – in more than 3,500 red giant stars. Most stars oscillate continuously because of sound waves bouncing back and forth inside them and they found 20% of the stars displayed signs of having strong magnetic fields that suppressed some of the oscillations.

“As our sample is so big,” Stello continued, “we have been able to dig deeper into the analysis and can conclude strong magnetic fields are very common among stars with masses of about 1.5-2.0 times that of the Sun. In the past we could only measure what happens on the surfaces of stars, with the results interpreted as showing magnetic fields were rare.”

Asteroseismology was used to enable astronomers to see the presence of very strong magnetic fields near the core of the star. They measured brightness variations of stars and found certain oscillation frequencies were suppressed by magnetic fields.

The next step is to directly test theories of how these strong magnetic fields form and evolve inside stars. This work could also potentially explain more about the factors involved in the 22 year magnetic cycle of the sun.

The research was published in Nature.