Concept of stellar evolution has been blown wide open

5 Jan 2016

An illustration of a strong magnetic field of a star. Image via ESO/L. Calçada

In what astronomers are calling an exciting discovery, the understanding of stellar evolution has been turned on its head after it was found that stars with an inner magnetic field are a lot more common than we thought.

Until now, much of our understanding of stellar evolution had been somewhat limited due to science’s measuring equipment’s ability to only measure activity on the surface of stars, but this has now been changed thanks to the introduction of a technique referred to as asteroseismology.

Using this new technique, a team from the University of Sydney used the Kepler telescope to pierce through the surface of stars, analysing the heart of the universe’s largest and most numerous nuclear reactors.

In doing so, they were able to determine that stars with incredibly strong magnetic fields are a lot more common than we once thought, with previous estimates believing that only a maximum of 5pc contained them.

But, according to the research team, 700 stars in one system were discovered to contain incredibly strong magnetic fields, ones that are typically around twice the size of that of our own sun.

Stellar evolution graph

A graph of the sizes of magnetic fields within different-sized stars. Image via University of Sydney

The ringing of the stellar bell

Publishing their findings in Nature, the lead of the Australian team, astrophysicist Dennis Stello, said: “Because only 5pc 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 as insignificant for our general understanding of stellar evolution. Our result clearly shows this assumption needs to be revisited.”

Using this astroseismology technique, the team was able to listen to the “ringing of the bell” that is emitted from the stars due to their magnetic fields, with the variation in sound revealing details of what’s happening beneath the surface.

When it then analysed the varying degrees of brightness emitted by the stars due to this ringing, it was found that particular oscillations were missing from 60pc of the stars analysed due to the magnetic fields.

By knowing the existence or strength of its magnetic field, it becomes easier to chart a star’s evolution and potential lifespan over the eons, however, the team says that the discovery now begs the question as to why stellar magnetic fields are so common.

Colm Gorey was a senior journalist with Silicon Republic