Astronomy Picture of the Day

Explanation: This shot captured an unexpected silhouette.   Which is it? It isn't the sunspots, the small dark regions caused by concentrated magnetic fields visible around the Sun's bright disk.   Sunspots typically last for weeks and were expected, since these spots were seen previously. It isn’t the International Space Station (ISS), the small dark structure on the middle left.  This is because the featured picture was planned with sub-second timing to record the iconic structure passing before the Sun. It was the airplane. Just as this exposure was taking place last month, from Prasek in the Czech Republic, an airplane began its own miniature partial eclipse. The result is this triply aligned image of our Sun. The photographer estimates that the chance of any random Sun image containing silhouettes of both a space station and an airplane, from that location, is about 30 million to one.