This STEREO image of the Sun in extreme ultraviolet light (June 9-10, 2007) showcases a string of active regions near the Sun's equator. We see several active regions (brighter areas with the loops above them) that were lined up as they approached the edge of the Sun.
Transits and eclipses are rare celestial events. Transits of Venus allow astronomers to calculate more accurately the distance of Venus from the Sun, and subsequently the distances of other planets. One can see the corona or atmosphere of the Sun safely with naked eyes only during a total solar eclipse.