Solar flares send a tremendous amount of light, energy and high-speed particles hurtling into space. They can last from minutes to hours and are monitored by NASA through X-rays and optical light. NASA rates solar flares according to their strength. From weakest to strongest, they are given an A, B, C, M or X rating. Each rating is 10 times stronger than the previous one.
To further fine-tune the scale, a number 1 through 9 is assigned to the rating. The ratings A through C are generally too weak to be noticed on Earth. An M rating may threaten astronauts and cause minor radio blackouts. NASA calls X-class flares “the biggest explosions in the solar system and awesome to watch.”
Just what can an X-class solar flare do? Producing as much energy as a billion hydrogen bombs, they can wreck havoc with our satellites and power grids. Pictured here is a massive X-class solar flare recorded by NASA on Aug. 9, 2011. Luckily, it sent particles streaming in the opposite direction from Earth.