Astronomy Picture of the Day . APOD: 2009 April 7 The Colliding Spiral Galaxies of Arp 274 . 7.04.2009 . ... This is because galaxies are mostly empty space and, however bright, stars only take up only a small fraction of that space. APOD: 2009 April 6 The International Space Station Expands Again . ... In a recently completed mission, the Space Shuttle orbiter Discovery visited the ISS and added components that included a new truss and new solar panels. ... First, a new truss was added. ...