Also known as the Seven Sisters, the star cluster M45—seen in a picture submitted May 7 to National Geographic's My Shot—contains more than 3,000 stars and is one of the brightest clusters known, according to NASA. At about 400 light-years away, M45 is also one of the closest star clusters to Earth.
A "supermoon" glows over Arkwright, New York, on May 5.
Due to the moon's egg-shaped orbit, there are times when the moon is at perigee—its closest approach to Earth—and at apogee, its farthest. The term "supermoon" was coined in 1979 to describe a full moon that coincides with perigee, a confluence that occurs about once a year, on average.
Noctilucent clouds glow over Alberta, Canada, in a picture submitted May 4 to National Geographic's Your Shot. The so-called night-shining clouds, shimmer even after dark, because they're so high in the atmosphere that sunlight reaches them even after the sun has dipped below the horizon.
The rare clouds are showing up at ever more southerly latitudes, and astronomers aren't sure why, according to NASA. Scientists suspect the increase may be due to climate change: Even as surface temperatures rise, the upper atmosphere is getting colder due to the buildup of carbon dioxide, creating perfect conditions for cloud formation, experts say.
Four hours later the Russian craft landed outside Arkalyk, Kazakhstan—carrying NASA astronaut Dan Burbank as well as Russian cosmonauts Anton Shkaplerov and Anatoly Ivanishin, who had spent more than five months on the space station.