This is the second of the two not-strictly astronomy pictures in this list, and is also taken from the International Space Station. It shows the Space Shuttle Orbiter Endeavour just minutes before docking with ISS. Both the ISS and Endeavour were orbiting the Earth at 8 km/sec (5 miles/sec), passing into the dark side of the Earth, essentially experiencing sunset - which they do 18 times a day!

This image is beautiful, of course, showing the layered colors of sunset as seen from 350km (210 miles) above the Earth's surface. But this picture is also a metaphor for the Shuttle itself: this was the second-to-last mission of the Endeavour, and in fact the last misson for the Orbiter will be the last mission for the entire fleet: after that flight, the Space Shuttle program will be finished, the Orbiters retired, and an as-yet unnamed rocket system will take over. In the meantime, American astronauts will hitch rides on Russian rockets, as well as on the Falcon 9 rocket from the private company SpaceX, which recently had a wonderfully successful test flight.

As for the Shuttle... the last launch of Endeavour is scheduled for April 2011, when it really will fly into the sunset for the last time.

Get the higher-res version here.

Image credit: NASA