The red dors seen around a total solar eclipse are called solar prominences or filaments jutting out from the sun. These are usually hidden from view just like the corona due to the brightness of the sun. A filament can extend thousands of kilometres with the largest on record estimated at over 800,000 kilometers long. Solar scientists knew they were in for a treat with the April 8, 2024 eclipse with the sun near solar maximum with lots of sunspots and activity.