Supernova Remnants Share a Connection With Our Milky Way Galaxy

May 31, 2016 | Joanne Kennell

The crab nebula, a supernova remnant
Photo credit: NASA Goddard Space Flight Center/flickr (CC by 2.0)

Supernova remnants are some of the most extreme environments in the universe.

What do supernovas and our Milky Way galaxy have in common? According to an international team of astronomers, supernovas can help us better understand the nature and shape of the Milky Way’s magnetic field.

It turns out that certain supernova remnants — what’s left after stars explode — are affected by the magnetic field of the Milky Way galaxy itself. “This study has shown that some supernova remnants -- ones that have a particular shape -- are aligned with the galaxy’s magnetic field lines,” said Jennifer West from the Faculty of Science at the University of Manitoba, and lead author of the study, in a CASCA 2016 press release.

Solar flares, stars, the evolution of the universe, and even Earth’s protection from damaging coronal mass ejections are, in part, a result of magnetic fields. But they also play a role in supernova remnants, which are some of the most extreme environments in the universe — so extreme that they have yet to be replicated in a lab.

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What happens in supernova explosions is that bubbles of particles are accelerated close to the speed of light, known as cosmic rays, which sometimes they find their way to Earth. Earth gets hit with trillions of these cosmic rays every single day, but the higher energy ones from supernova remnants are what can cause problems. These supernova remnants can interfere with electronic equipment and can even be hazardous to people.

According to astronomers, many supernova remnants are double-lobed objects that look like two facing hamburger buns, with the invisible “burger” axes aligned with the local magnetic fields.

To find a connection between the remnants and magnetic fields, the researchers examined archived radio images of every known supernova remnant in the galaxy — about 300. They discovered that 80 of them were double-lobed in shape, but their hamburger axes were pointed in different directions. However, astronomers were not sure if these orientations were random or whether the direction was influenced by the Milky Way’s own magnetic field.

By comparing the orientation of the remnants in the images with models based on simulations of our Milky Way galaxy’s magnetic field, the team found that the supernova remnants depended not only on the orientation of the magnetic field, but also on their distance from the sun.

Samar Safi-Harb, West’s doctoral thesis advisor, explained that, “West’s research further stresses the importance of studying supernova remnants, which not only host the heavy elements we are made of, but also help us understand the interplay between these fascinating objects and cosmic magnetism.”

Although the results are preliminary, they could help astronomers better understand supernova remnants, as well as our galaxy’s magnetic field.

The paper was published in the journal Astronomy & Astrophysics and online at arXiv.org.

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