It also is the 400th anniversary of Galileo's first recorded astronomical observations. ... Smithsonian Opens Observatory On National Mall. October 1, 2009 5:40 AM ET.

To mark this anniversary and in conjunction with the International Year of Astronomy, the Smithsonian’s National Air and Space Museum will open its Public Observatory this week. The observatory ...

Thanks to the Chandra X-ray Observatory and a new project from the Smithsonian, a new 3-D viewer will allow users to explore Cassiopeia A.