Scientists used these observations of the sun's atmosphere from NASA's Solar Terrestrial Relations Observatory on Aug. 5, 2007 to define the outer limits of the solar atmosphere, the corona.
Scientists used these observations of the sun’s atmosphere (the bright light of the sun itself is blocked by the black circle at the middle) from NASA’s Solar Terrestrial Relations Observatory on Aug. 5, 2007, to define the outer limits of the solar atmosphere, the corona. STEREO’s findings show a corona extending out some 5 million miles above the sun’s surface. Credit: NASA/STEREO