The solar wind is the sun's outer atmosphere expanding into space. (scientificamerican.com)
The spacecraft's telescopes are sensitive to radiation from the hot outer atmospheres of stars like the Sun and white dwarfs, formed when stars about the size of the Sun reach the end of their lives. (newscientist.com)
As the bloated star ages, this extended outer atmosphere cools and contracts, then soaks up more energy from the star and again puffs out: with each successive cycle of expansion and contraction the atmosphere puffs out a little farther. (discovermagazine.com)