...yet I didn't know it. I was reading about this weekend being a good time to observe Saturn, and saw: It is from such occultations that we learned the particulate nature of Saturn's rings.

From Collins Dict.: occultation (ˌɒkʌlˈteɪʃən)
Definitions
noun
1.the temporary disappearance of one celestial body as it moves out of sight behind another body
2.the act of occulting or the state of being occulted

Collins

I will say in my defense that Onelook had only a handful of offerings for this word.