Mysterious structures in the sky that have puzzled astronomers for decades may finally have an explanation—and it’s quite a few.
The north polar spur and fan regions, on opposite sides of the sky, may be linked by a vast system of magnetic filaments. These form a tunnel-like structure that encircles the Solar System, and in addition many nearby stars.
“If we looked up into the sky, we would see this tunnel-like structure in almost every direction – that is, if we had eyes that could see radio light,” said astronomer Jennifer West of the University of Toronto in Canada.
We’ve known about both structures for a long time—since the 1960s, in fact—but they are difficult to understand. That’s because it’s hard to know exactly how far apart they are; The distance is hundreds to thousands of light years away.
However, no analysis had ever linked the two structures together. West and his colleagues were able to show that the major radio loops in the two regions and the space between them could be connected, solving many of the complex problems associated with both.
“A few years ago, one of our co-authors, Tom Landeker, told me about a 1965 paper from the early days of radio astronomy. Based on the raw data available at this time, the authors (Matthewson and Milne), hypothesized that these polarized radio signals may originate from within, in our view of the local branch of the Milky Way,” West explained.
“That paper inspired me to develop this idea and link my model to the better data that our telescopes give us today.”
Using modeling and simulations, the researchers mapped out what the radio sky would look like if the two structures were connected by magnetic filaments, playing with parameters such as distance to determine the best fit.
From this, the team was able to determine that the most likely distance from the Solar System to the structures is about 350 light-years, which is consistent with some close estimates. This includes an estimate of the distance to the north polar spur earlier this year based on Gaia data that found almost all spurs are within 500 light-years.
The entire length of the tunnel created by West and his team is about 1,000 light years.
This model is in agreement with a wide range of observational properties of the north polar spur and fan region, including size, polarization of electromagnetic radiation (that is, how the wave is twisted), and brightness.
“It’s a very clever piece of work,” said astronomer Brian Gensler of the University of Toronto.
“When Jennifer first told me this, I thought it was too ‘out there’ for a possible explanation. But she was finally able to convince me! Now I’m excited to see how the rest of the astronomy community reacts.” Is. “
More work is needed to first confirm the findings, and then model the structure in more detail. But doing so could help solve an even bigger mystery: the formation and evolution of magnetic fields in galaxies, and how these fields are maintained. This, the researchers said, could provide context for understanding other magnetic filamentary structures found around the Milky Way.
The team plans to do more complex modeling; But, they suggest, more sensitive, higher-resolution observations will help reveal hidden details that show how the structure fits into the broader galactic context.
“Magnetic fields do not exist in isolation. They must all be interconnected. So the next step is to better understand how this local magnetic field connects to both the large-scale galactic magnetic field and the small-scale magnetic field. Ours of the Sun and the Earth,” West said.
“I think it’s awesome to imagine that these structures are everywhere, whenever we look up at the night sky.”
is due to appear in research The Astrophysical Journal, and is available on arXiv.
cover image credit: Dominion Radio Astrophysical Observatory/Villa Elisa Telescope/ESA/Planck Collaboration/Stellarium/J. West