Summary
A foe is a unit of energy equal to 10^44 joules or 10^51 ergs, used to measure the large amount of energy released by a supernova.
The word is an acronym derived from the phrase [ten to the power of] fifty-one ergs.
This unit of measure is convenient because a supernova typically releases about one foe of observable energy in a very short period (which can be measured in seconds). In comparison, if the Sun had its current luminosity throughout its entire lifetime, it would release 3.827×10^26 W (Symbol for Watt) × 3.1536×10^7 s/yr × 10^10 yr ≈ 1.2 foe.
Others
Big Bang
Observable Universe.