Astronomy:Foe (unit)

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A foe is a unit of energy equal to 1044 joules or 1051 ergs, used to express the large amount of energy released by a supernova.[1] An acronym for "[ten to the power of] fifty-one ergs",[2] the term was introduced by Gerald E. Brown of Stony Brook University in his work with Hans Bethe, because "it came up often enough in our work".[3]

Without mentioning the foe, Steven Weinberg proposed in 2006 "a new unit called the bethe" (B) with the same value, to "replace" it.[4]

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 3.827×1026 W × 3.1536×107 s/yr × 1010 yr ≈ 1.2 foe. One solar mass has a rest mass energy of 1787 foe.

See also


  1. Hartmann DH (April 1999). "Afterglows from the largest explosions in the universe". Proc. Natl. Acad. Sci. U.S.A. 96 (9): 4752–5. doi:10.1073/pnas.96.9.4752. PMID 10220364. Bibcode1999PNAS...96.4752H. 
  2. "Neutrinos and Supernovae". Los Alamos Sciences. Los Alamos National Laboratory. October 25, 1997. 
  3. Gerald Brown (2006). Hans Bethe and His Physics. World Scientific. ISBN 981-256-609-0. 
  4. "Following the death of Hans Bethe last year, I have proposed a new unit called the bethe, where 1 B is 1051 ergs or 1044 J. This would replace the unit of 1051 ergs, which is commonly used by those studying supernovae – a field in which Bethe worked. Ian Mills, president of the consultative committee on units of the International Committee for Weights and Measures, has concurred and agreed that the bethe can be used." Stephen Weinberg (2006). "A Bethe unit". Physics World 19 (2): 17. doi:10.1088/2058-7058/19/2/31.