Discovered by Matt Shultz, PhD student of Queen’s University in Ontario (Canada) and his team. Researchers have identified the presence of magnetic fields in the components of the binary star Epsilon Wolves , the fourth brightest star in the constellation of the Wolf, in the Southern Hemisphere. The stars, orbiting around each other, are located at a distance of about 500 light years from Earth, each have a mass between seven and eight times that of our Sun and, together, have a luminosity 6,000 times greater.
The discovery was made thanks to the observations of the telescope Canada-France-Hawaii , which were conducted as part of the research activities of the consortium BinaMIcS (binarity and Magnetic Interactions in various classes of Stars), coordinated by the University of Evelyne Alecian Grenoble, France, with the objective of studying the magnetic properties in close binary star systems.
Shultz said: “The origin of magnetism in massive stars is still a mystery, and this discovery could help shed light on why only some stars have magnetic fields of great size.”
In stars with a surface temperature relatively low, such as the Sun, magnetic fields are generated by an effect “dynamo”. To feed it are the convective motions that develop inside the star, where the hotter material rises to the surface while the colder air falling in the deepest areas. In massive stars, the hottest and brightest at the surface, the convective motions are substantially absent and consequently also the dynamo effect. There must therefore be some other mechanism responsible for the magnetic field in the star Epsilon wolves.
Astronomers argue for two possible explanations , both linked to the concept of ‘fossil magnetic field’, which would be formed in the past that the evolutionary history of the star and then keep to this day. The first hypothesis predicts that the magnetic field is just emerged during the stages of formation of the star, the second suggests that the magnetic field has been produced by the effect dynamo caused during a violent mixing of stellar material occurred as a result of a merger of two stars already formed.
“Our discovery allows us to rule out the scenario of the merger from a binary system,” adds Schultz. “However, it does not change the view that emerges from the results so far of cooperation BinaMIcS, ie that less than two percent of massive stars in close binary systems possess magnetic fields. And we do not yet know why. ”
The survey, published in the journal Monthly Notices of the Royal Astronomical Society , indicates that the intensity of the magnetic fields in the two stars are similar, but their axes are anti-aligned with the south magnetic pole of a star that points in the same direction as the north pole of the other, leaving open the possibility that the two stars share a single global magnetic field. The results also indicate that the stars are close enough because their magnetospheres can interact during the orbital motion. Their magnetic fields could then act as a giant brake which, in the long run, would bring more, and then blend.