Image of a Solar Prominence
A solar prominence observed on 2 June 2015 at 13:51 UT (8:51 am CDT)
From time to time, tremendous explosions on the Sun known as solar flares happen and are classified as X-ray class B, C. M, or X according to their X-ray peak flux. Class B and C are minor flaring events, Class M are moderate, and anything above M6 is consider a major flare. X-class flares are the most powerful.
Note: Currently (4 May 2018) the Sun is very quiet with no spots visible and very few filaments or prominences as we begin to move into the solar minimum period. So far 73 days this year or 59% of the time have been spotless. The below graphic, from www.spaceweather.com and NOAA shows where we are at and where we are headed in the solar cycle.
Never look directly at the Sun without proper eye protection.