A Canadian graduate student recently made a remarkable discovery — two massive stars with mysterious magnetic fields that make up a binary system. As a report from the Queen’s Gazette notes, a binary star is a star system consisting of two stars orbiting around their common center of mass.
Matt Shultz from Queens University, which is located in Ontario, Canada, was the first to discover that the two giant stars in that binary system — Epsilon Lupi — have magnetic fields. He reported his findings in the Monthly Notices of the Royal Astronomical Society.
Schultz is a member of the consortium BinaMIcS (which stands for Binarity and Magnetic Interactions in various classes of Stars), and was studying the magnetic properties of close binary star systems. The research was headed by Dr. Evelyn Alecian from the University of Grenoble in France. This collaboration is studying the magnetic properties of close binary stars using the Canada-France-Hawaii Telescope, which is located atop the summit of Mauna Kea in Hawaii.
Epsilon Lupi is the fourth brightest star system that lies in the southern constellation of Lupus. This pair of stars is located at a distance of about 500 light years from Earth. Epsilon Lupi is composed of two blue stars that each have between 7 and 8 times the mass of the Sun, and the total luminosity of the two stars in the system exceeds the luminosity of the sun by 6,000 times. It is also the 250th brightest star system in the Earth’s sky. Astronomers have known about the existence of Epsilon Lupi for years, but did not know that the two giant stars have strong magnetic fields.
The origin of magnetic fields in cooler stars, such as our Sun, is explained by convection processes such as dynamo mechanism which, however, does not take place inside hotter, bigger stars. However, about 10 percent of massive stars have a powerful magnetic field.
To explain the origin of the magnetic fields of Epsilon Lupi, two hypotheses were offered. The first hypothesis was that the magnetic field was generated during the formation of the star and was subsequently locked in to the star’s outer portion. According to Science Daily, the second is that the magnetic field originates in dynamos driven by the violent mixing of stellar plasma when the two stars in a close binary merge.
“This discovery doesn’t change the basic statistics that the BinaMIcS collaboration has assembled,” Shultz explained, “and we still don’t know why there are so few magnetic, massive stars in close binaries.”
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