Astronomy Picture of the Day

Explanation: It is the largest and most sophisticated object ever built off the Earth. It has taken numerous spaceflights and over a decade to construct. The International Space Station (ISS) is currently the premiere habitat for humans in Earth orbit, and an amalgamation of sophisticated orbiting laboratories that have examined everything from the formation of new materials and medicines created in microgravity -- to the limitations of the human body -- to the composition of the universe. This month, the ISS is celebrating 15 years of continuous human habitation. The ISS has been visited by astronauts from 15 countries, so far, and has international partners led by NASA (USA), Roscosmos (Russia), CSA (Canada), JAXA (Japan), and ESA (Europe). The featured animation shows the piece-by-piece construction of the ISS from 1998 to 2011. Spanning the length of a football field, the ISS can be seen as an unusually bright spot drifting slowly overhead by anyone who knows when and where to look.