... Microwave Hotspots: The Oldest Structures Known . ... They are seen on the above two images of the microwave sky, north and south of our galaxy's equator, based on four-year's worth of data from NASA's COsmic Background Explorer (COBE) satellite (1989-1993). The spots represent temperature variations in the early universe. ... During the Astro-1 astronomy mission of December, 1990, Space Shuttle astronauts photographed this stunning view of the full moon rising above the Earth's limb. ...