South Korean President Park Geun-hye walks past a NASA logo during a tour of projects and programs that are underway at the agency's Goddard Space Flight Center, Wednesday, Oct. 14, 2015, in Greenbelt, Md. (AP Photo/Patrick Semansky)

Watch as Mercury transits across the sun

Mercury will take more than seven hours to traverse the sun completely. Mercury’s last transit was in 2006, and the next journey isn’t until…