As most space-loving Earthlings sought out Mercury's silhouette against the sun on May 9, one photographer waited in anticipation for something else to cross the sun's bright disk: the International Space Station.
Thierry Legault, a photographer from France, flew thousands of miles to witness the rare event as Mercury crossed in front of the sun. That planetary crossing, known as a transit, won't happen again until 2019, but Legault wanted to capture an even rarer sight: the space station crossing the sun during the transit of Mercury. That juxtaposition would be visible in only three locations: Quebec, Canada; Florida; and the Great Lakes area of the U.S. Legault's final destination took a lot of deliberation, but he settled on the suburbs of Philadelphia where the skies would likely be clear and he could find a quiet space.
The journey was a gamble, Legault said, because the space station crosses the sun in less than a second, meaning any clouds can easily ruin the shot. (Check out more awesome photos of Mercury crossing the sun.)
"Adrenaline flows in the moments before the station flies by — it is a one-shot chance," Legault said in an image description. "I cannot ask the space agencies to turn around so I can try again. Anything can happen."
Legault chose well. The image above includes frames superimposed on each other to show the station's path, with Mercury appearing as the black dot seen toward the bottom of the sun's center. But Lagault was also lucky: Only 10 minutes after he shot the photos, the clouds rolled in.
"Astrophotography is my hobby that I spend many hours on, but even without a camera I encourage everybody to look up at the night sky," he said. "The International Space Station can be seen quite often, and there are many more things to see. It is just a case of looking up at the right time." (You can see more of Legault's astrophotographer at his website here.)
Space.com's Satellite Tracker Map, made by N2YO, shows the current location of the International Space Station and other satellites, and when they'll next pass over your location.
Follow Shannon Hall on Twitter @ShannonWHall. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.