Foe (unit)

{{Short description|Unit of energy}} 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.<ref>{{cite journal |author=Hartmann DH |title=Afterglows from the largest explosions in the universe |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=96 |issue=9 |pages=4752–5 |date=April 1999 |pmid=10220364 |doi= 10.1073/pnas.96.9.4752|bibcode = 1999PNAS...96.4752H |pmc=33568|doi-access=free }}</ref> An acronym for "[ten to the power of] '''f'''ifty-'''o'''ne '''e'''rgs",<ref> {{cite web |url=http://library.lanl.gov/cgi-bin/getfile?25-14.pdf |title=Neutrinos and Supernovae |author1=Marc Herant |author2=Stirling A. Colgate |author3=Willy Benz |author4=Chris Fryer |date=October 25, 1997 |work=Los Alamos Sciences |publisher=Los Alamos National Laboratory |access-date=2008-04-23 |archive-url=https://web.archive.org/web/20090114233021/http://library.lanl.gov/cgi-bin/getfile?25-14.pdf |archive-date=2009-01-14 }} </ref> 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".<ref> {{cite book |url=https://books.google.com/books?id=HaL-NNHBmM0C |title=Hans Bethe and His Physics |author=Gerald Brown |year=2006 |publisher=World Scientific |isbn=981-256-609-0 }} </ref>

Without mentioning the foe, Steven Weinberg proposed in 2006 "a new unit called the '''bethe'''" (B) with the same value, to "replace" it.<ref name=weinberg2006>"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." {{cite journal |doi= 10.1088/2058-7058/19/2/31 |title= A Bethe unit |author= Stephen Weinberg |journal= Physics World |volume= 19 |number= 2 |year= 2006 |page= 17 }} </ref>

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's current luminosity is the same as its average luminosity over its lifetime, it would release 3.827{{e|26}} W × 3.1536{{e|7}} s/yr × 10¹⁰ yr ≈ 1.2 foe. One solar mass has a rest mass energy of 1787 foe.

==See also== * Orders of magnitude (energy)

==References== {{Reflist}}

{{Supernovae}}

Category:Units of energy Category:Supernovae

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