Jansky
The jansky (symbol Jy) is a non-SI unit of spectral flux density, or spectral irradiance, used especially in radio astronomy. It is equivalent to 10−26watts per square metre per hertz.
The flux density or monochromatic flux, , of a source is the integral of the spectral radiance, , over the source solid angle:
The unit is named after pioneering US radio astronomer Karl Guthe Jansky and is defined as
Since the jansky is obtained by integrating over the whole source solid angle, it is most simply used to describe point sources; for example, the Third Cambridge Catalogue of Radio Sources (3C) reports results in Jy.
Jansky units are not a standard SI Unit, so it may be necessary to convert the measurements made in the unit to the SI equivalent in terms of watts per square metre per hertz (W/(m2·Hz)). However, other unit conversions are possible with respect to measuring this unit.
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