The mysterious star that turns into a giant magnet

The Milky Way always hides unexpected treasures, strange celestial bodies, with properties never seen before. Which can shed new light on certain gray areas.

This is what is happening thanks to a pair of stars, but it was observed just over a century ago, located in the constellation of the Unicorn, more than 3,000 light-years from Earth. The pair, named “HD 45166”, consists of two fairly massive stars, respectively 3.4 and 2 times the mass of the Sun, orbiting each other in one hundred and twenty-eight days. The lightest member of the binary could explain one of the mysteries of the universe: the formation of compact objects like a black hole and the emitting of a huge magnetic field, magnetars. By “giant” we’re talking about more than 10 billion tesla, or about 1,000 billion times more than the average magnetic field of the Sun, or 200,000 billion times more than Earth’s.

These magnetic stars, of which more than two dozen are observed in our galaxy, belong to a large family of neutron stars, which are very dense stars with a radius of ten kilometers, but they weigh one and a half times more than the Sun. This is how giant stars end their lives, having burned out hydrogen and collapsing in on themselves. Pulsars are special neutron stars that emit regular radio waves towards Earth. Magnets are another class, endowed with magnetic fields of very intense intensity, but of unknown origin.

“Obsession HD 45166”

This is where HD 45166 and Int Fifteen Researchers who publish their observations in scienceAugust 17. “I was obsessed with HD 45166 for several years, because what we knew about this system just wasn’t right. I read everything that happened about it., recalls Tomer Schnar, today at the Center for Astrobiology in Madrid. Officially, the least massive star in the HD 45166 system has been designated a Wolf-Rayet star, a star made of helium, which has lost hydrogen and spewed strong winds, ejecting surrounding material several hundred kilometers an hour. “But it was less luminous than the others in this class. Its winds were ten times less intense.”notes Tomer Schnar who adds that its light signature, or spectrum, does not correspond to its family either: in addition to helium, there is a lot of carbon, oxygen, nitrogen … In addition, this spectrum is very variable over time, some elements literally disappear.

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