The distance to the North Polar Spur
One of the largest structures in the Milky Way galaxy, the North Polar Spur, was discovered at radio and X-ray wavelengths. The Spur is a giant ridge of bright emission that rises roughly perpendicularly out of the plane of the galaxy starting roughly in the constellation of Sagittarius and then curves upward, stretching across the sky for over thirty degrees (the size of sixty full-moons) where it appears to join other bright filamentary features. The emitted radiation is highly polarized, indicative of its being produced by ionized gas in the presence of strong magnetic fields. Depending on how far away the Spur is from us, its length estimates range from hundreds to thousands of light-years.
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2021-03-01
