The heliosphere, influenced by the sun, blocks many cosmic rays from reaching our solar system’s planets. The sun, a star emitting a steady stream of plasma known as the solar wind, also releases coronal mass ejections and flares. This area is over a hundred times larger than the distance from the sun to Earth. Sarah Spitzer, a research fellow at the University of Michigan, contributed to this article originally published at The Conversation and featured on Space.com.