Artist’s impression of HD 45166, an unusually magnetic star.Shows how a powerful wind of particles blown away from a star can be trapped in a magnetic field.
ESO/L. Kalkada
A new type of star may solve the mysteries of the universe. After a century of research, astronomers have finally figured out why a star called HD 45166 looks so strange. This could be the key to understanding where the strange stars called magnetars came from.
HD 45166 is about 3000 light-years away in a binary star system and is a type of object called a Wolf-Rayet star. It is also known as a helium star because the hydrogen in its outer layer has been blown away to expose the underlying helium. But it didn’t look like any other Wolf Raie star we’ve seen so far. “This star has been known to be a strange star for about 100 years,” he said. Tomer Shenner at the University of Amsterdam, the Netherlands. “It didn’t make sense. It really contradicted the theory and needed more scrutiny.”
Shenner and his colleagues are now making a series of new observations of the star, delving into its light spectrum to learn more about how it works. They found that the star has a very strong magnetic field, stronger than any other star of the same size that has been measured so far.
The outflow of goods HD 45166’s odd appearance is probably because it is actually trapped in its magnetic field and not drifting away like normal Wolf-Rayet stars. “Most of the material we see up close is trapped in arcs that travel between the star’s poles and collide in the middle,” Shenner said. “You can see this thick ball of gas, and sometimes you can see the actual star through it.”
These strong magnetic fields mean that when this star collapses in a few million years, it will likely become a magnetar, the neutron star with the strongest magnetic field in the universe. About 10 percent of neutron stars are magnetars, but exactly how magnetars form has been a mystery for decades. If stars like HD 45166 eventually turn into magnetars, the mystery is finally solved.
There are two next steps for Shenner and his team. By continuing to observe the binary system for several more years, we will be able to better understand the properties of the star and, by extension, its ultimate fate. They also plan to search for more of these magnetized helium stars. According to their calculations, there should be hundreds in our galaxy. More discoveries at different stages of stellar evolution may eventually help us figure out how magnetars actually form.
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