Epsilon Lupi’s magnetic field is apparently proving some star formation theories wrong. About half of the stars in our galaxy are paired together as binary star systems, which means that two stars are orbiting a common center, but Epsilon Lupi is considered special because it is composed of two massive stars with magnetic fields. This is considered quite a mystery, since massive stars lack our Sun’s strong convection process, which allows it to generate a strong magnetic field.
In a related report by the Inquisitr, NASA’s Hubble telescope found a double black hole lurking in a nearby quasar, and they claim the discovery allows researchers to systematically search for binary black holes in space. In recent times, NASA’s New Horizons probe began sending back high resolution photos of Pluto and its moons, and some scientists hope for evidence of “alien” life in space.
The discovery of Epsilon Lupi’s magnetic field was made by the BinaMIcS (Binarity and Magnetic Interactions in various classes of Stars) collaboration, which was formed to study the magnetic fields of close binary star systems. Epsilon Lupi, or HD 136504, is a bright binary located about 500 light years away from Earth. Each star in Epsilon Lupi is more than seven times larger than the Sun, and together, the binary star system is 6,000 times as luminous.
One problem. Epsilon Lupi’s magnetic field system should not exist, according to some theories on star formation.
“Observations can be approximately reproduced by a model assuming the magnetic axes of the two stars are anti-aligned, and roughly parallel to their respective rotation axes,” explained the study on Epsilon Lupi’s magnetic field, as published by arXiv. “Estimated magnetospheric radii indicate a high probability that their magnetospheres are interacting. As many of the arguments for the different proposed formation scenarios of fossil magnetic fields rely upon evidence drawn from investigations of close binaries, in particular the rarity of magnetic ABO stars in close binaries and the previous absence of any known close binary with two magnetic, massive stars, this discovery may be an important new constraint on the origin of fossil magnetic fields.”
When it comes to the Sun, we know the magnetic field is generated by a strong convection process in the star’s outer layer. But massive stars like Epsilon Lupi lack a similar convection process, since their envelopes cannot support a magnetic dynamo. The reason that a massive star with a magnetic field is considered an issue is because around 10 percent of massive stars in our galaxy have been discovered to have a strong magnetic field.
There are two competing explanations for how this could be, although both assume the concept of a “fossil” magnetic field. The basic concept is that a magnetic field was generated in the distant past and yet became locked onto the star’s surface. The first hypothesis is that the magnetic field of a massive star is generated while it was forming. The second hypothesis considered the possibility that a close binary system could generate this field based upon the interaction of stellar plasma when first merging.
But Epsilon Lupi’s magnetic field seemingly upsets the second idea, since the alignment of their magnetic axes is the exact opposite. According to Matt Shultz of Queen’s University, this discovery rules out the binary merger hypothesis, but does not explain the greater mystery.
“The origin of magnetism amongst massive stars is something of a mystery,” says Shultz, according to the Queen’s Gazette. “This discovery doesn’t change the basic statistics that the BinaMIcS collaboration has assembled.”
As for why the axes of Epsilon Lupi’s magnetic field is anti-aligned, Schultz just says more research is needed.
“We’re not sure why that is yet, but it probably points to something significant about how the stars are interacting with one another,” he said. “We’ll need to collect more data.”
The research on Epsilon Lupi’s magnetic field was first published in the Monthly Notices of the Royal Astronomical Society.
[Image via Sci-News]