If it has to do with the universe, it's cosmic. The planets, for instance, are cosmic bodies.
When you use the word cosmic to describe something big, you often use it with the word, proportions. A big mistake might be an error of cosmic proportions. In the 1960s, when humankind had been exploring space for about 10 years, the word cosmic became commonly used to describe things that might be considered "far out" or groovy. Like wow, man!