Adding foe as a unit to astropy.units

[johntkappel]

Description

The foe is an uncommon unit of energy used in astrophysics, which is equivalent to 10**51 ergs (Fifty-One Ergs - FOE). It is equivalent to the energy released by a supernova, and so is occasionally used. It is also referred to as a Bethe, though this is less common.

Example of implementation would be: def_unit(['Foe', 'foe','Bethe','bethe'], cgs.erg ** 51, namespace=_ns, prefixes=True)

Additional context

Either units.cgs or units.misc would be the appropriate place to implement this feature.

The term was originally proposed by Hans Bethe. Examples of using foe and bethe as units: https://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-UR-97-2534-14 https://www.sciencedirect.com/science/article/pii/0375947496002345 https://iopscience.iop.org/article/10.3847/1538-4357/abf82e/meta

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[mhvk]

Yes, I think that would be fine to add. Probably best in astrophys,py. PR welcome, but note that the definition is not quite right: should be 1e51 * erg. Also, at least for foe, there should be no prefixes; I think this would be best for Bethe too. And I would not include "Foe" with a capital - I've only seen it in all lower case.