Most of the facts about the sun known to us today are fairly recent, coming after the invention of the telescope, photography, spectroscopy, and the launching of satellites.
It appears that the earliest working models of the telescope seem to have been invented by Hans Lippershy in 1608. Just a year later, Galileo was using these devices to do incredible research, helping him discover that the sun was rotating – and fully convincing him that the Heavens were governed by predictible movement. This lead to his later assertion, that the Earth moves around the sun - one of the most basic facts about the sun.
However it wasn't until the invention of photography and spectroscopy in the 19th century, combined with proper record keeping, that proper solar research could begin, and we could finally learn some more useful facts about the sun.
On September 1st, 1859, a British astronomer observed and recorded for the first time a major coronal mass ejection / solar flare, now known as the “Carrington Event”. As the radiation from the storm hit the Earth it knocked out telegraphs - the world’s first electromagnetic-based communications system. Since then a number of solar storms have demonstrated the fragility of our electronic communications and power systems.
Click on the following links to learn more about Coronal Mass Ejections or about why NASA and other scientists are concerned that an even worse scenario than what happened in 1859 could occur in 2012.