Perihelion is a noun that refers to the highest point or the peak.

The Greek prefix P-E-R-I means ‘near,’ while the word helios (HE lee ose) — also from Greek — means ‘the sun.’ The word is often used in specifically scientific contexts, but can also, more figuratively, refer to the peak or highest point of something. For example:

I felt our band’s first show was our perihelion, but then again, as it was our only show, it makes sense that I would regard that as our peak of success.