NASA's sun-watching Solar Dynamics Observatory recorded dramatic vide that showed the flare in extreme detail.
"This is the strongest flare seen so far in 2013," NASA spokeswoman Karen Fox said in a statement. She noted the sun has been relatively calm lately, but it's heading into a peak activity period.
"Increased numbers of flares are quite common at the moment, since the sun's normal 11-year cycle is ramping up toward solar maximum, which is expected in late 2013," Fox said.
Today's M-class solar flare was an estimated 10 times weaker than the strongest X-class flares.
Still, M-class flares can still trigger space weather effects near Earth, such as the atmospheric displays known as the northern lights or radio frequency disturbances.