The Nebra sky disk is a bronze disk of around 30 cm diameter, with a blue-green patina and inlaid with gold symbols. These are interpreted as a sun or full moon, a lunar crescent, and stars (including a cluster interpreted as the Pleiades).
Theese are NOT viking runes. They are an older Rune alphabet, from around year 500 and earlier. They are called the elder futhark. The viking Rune alphabets have usually only 16 runes and there are several different alphabets from that time.