A distorted sun with a "blemish" on its face rises over the Caspian Sea in a picture of the 2012 transit of Venus taken from the shores of Azerbaijan on Wednesday.
During the transit—the last one until 2117—Venus crossed between Earth and the sun, so that observers could see a black dot gliding over the solar disk. The sun appears squashed in this frame because more of its light is being bent by the thick layers of Earth's atmosphere.
Scientifically, the most important parts of a Venus transit are the moments when the planet appears to enter and leave the sun's disk, according to astronomer Jay Pasachoff of Williams College in Massachusetts.
Timing exactly when the planet crossed the solar limb from different locations helped 18th-century astronomers more precisely measure the distance between Earth and the sun. Scientists hope to use data collected during the 2012 Venus transit to study the planet's upper atmosphere.
Image courtesy SDO/NASA
The star cluster M13, also known as the Great Globular Cluster in Hercules, shines in a picture snapped by a backyard astronomer and recently submitted to National Geographic's My Shot photography community.
Located 25,000 light-years from Earth, the spherical collection of hundreds of thousands of old stars is one of the brightest globular clusters in the northern sky.
Likely left by commercial jets, contrails crisscross the skies near the coast of Newfoundland, Canada, in a recently released picture from NASA's Terra satellite.
Contrails tend to appear in the wakes of passing aircraft, when extra particles and water vapor in their exhaust serve as the seeds for cloud formation.
Image courtesy Jeff Schmaltz, MODIS/NASA
Clash of the Titans
An illustration shows the possible view from Earth when the Andromeda Galaxy (left), our largest galactic neighbor, collides with the Milky Way.
Astronomers using the NASA-ESA Hubble Space Telescope announced last week that they can more accurately predict what the galactic collision will look like—even though it won't happen for another four billion years.