Massive Magnetic Loop Found in Binary System

The two stars are in the Milky Way

By Tudor Vieru on January 14th, 2010 07:39 GMT
For the first time ever, astronomers have managed to discover a giant magnetic loop forming between the components of a binary star system inside our galaxy, the Milky Way. The finding is tremendously important, because it shows this type of events can also take place in stars other than our Sun, hinting at the fact that they could be going on throughout the Universe. The Algol system features members that are more massive than our own, so astronomers hope that their findings will hold true in the case of larger stars as well, Space reports.

“This is the first time we've seen a feature like this in the magnetic field of any star other than the Sun,” University of Iowa researcher William Peterson explains. Experts add that the Algol binary system has been known since ancient times as The Demon Star. They explain now that this name came from the fact that the structure appeared to blink when people looked at it from the Earth. This happens as one of the stars moves in front of the other, briefly reducing its apparent brightness. This type of phenomena is called occultation, and is used extensively in searching for exoplanets.

Because Algol is located just some 93 light-years away from our own planet, it is clearly visible in the night sky. The system features two stars, of which one is about three times heavier than the Sun. This is the main one, and it keeps the smaller star orbiting around it. The small body spins around its companion at a distance of about 5.8 million miles, which is roughly six percent of an astronomical unit (AU), the distance from the Earth to the Sun. Because of this close proximity, the small star always has the same face oriented towards the larger one, which in effect means that the binary system is tidally locked. To put things into perspective, the Moon is also tidally locked with our planet, as gravitational pulls ensure it always keeps the same face aimed at us.

Scientists have discovered that the smaller companion's poles generate vast magnetic loops, which are naturally directed at the larger star. In order to be able to make these highly detailed observations of Algol, researchers had to use the High Sensitivity Array. This is a collection of some of the most advanced telescopes in the world today, and includes the US-wide Very Long Baseline Array (VLBA), operated by the National Science Foundation (NSF), the New Mexico-based Very Large Array, the Effelsberg radio telescope in Germany, as well as the Robert C. Byrd Green Bank Telescope, which is located in West Virginia. Together, these observatories can resolve even the smallest details, particularly in radio wavelengths.

Though Algol was discovered in 1667 by an Italian astronomer, it wasn't until 1889 that its true nature was finally revealed. It was only then that scientists were able to establish that it was an eclipsing binary, and not some supernatural manifestation. The Eye winks once every three days, astronomers report. Details of the recent investigation can be found in the January 14 issue of the journal Nature.
Artist's rendition of the two stars in the Algol binary system, showing superimposed data collected from the HSA
   Artist's rendition of the two stars in the Algol binary system, showing superimposed data collected from the HSA
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