B radiationfromthesun, That's theultravioletradiationfromthesun.
WhathappensisithitsyourskingetsabsorbedbyyourdermisandtheepidermiscausesDNAdamage, causesinflammation, causes a sunburn, whichisessentiallysortoflike a callusesthat's createdonyourskinfrombeingburnt.
Butastronomerspredictthat 10 trillionsof a sunburnisactuallyfromstarsoutsideofourgalaxy.