The Eridanus Void. This area shows almost no signs of cosmic matter, meaning no stars, planets, solar systems or clouds of cosmic dust. Researchers couldn't even find dark matter, which is invisible but measurable by its gravitational pull. There were also no signs of black holes that might have gobbled up the matter once present in the region.
When we see an auroral arc – and associated rays – we're really seeing a small section of the much larger, permanent aurora called the auroral oval. The northern oval is centered over the geomagnetic north pole located in northern Canada. Credit: NASA