Jansky

In radio astronomy, the flux unit or jansky (abbreviation Jy) is a non-SI unit of electromagnetic flux equivalent to 10−26 watts per square metre per hertz. The unit "jansky" is named after the pioneering radio astronomer Karl Jansky.

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The brightest natural radio sources have flux densities of the order of one (to one hundred) janskies, which makes the jansky a suitable unit for radio astronomy.

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For example the Third Cambridge Catalogue (3C) which was prepared in 1959 and revised in 1962, lists some 300 to 400 radio sources in the Northern Hemisphere brighter than 9 Jy at 159 MHz.

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1 Jy = 10-26 W m-2 Hz-1 (SI)

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1 Jy = 10-23 erg s-1 cm-2 Hz-1 (cgs)

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Converting an AB magnitude to microjanskies is straightforward:

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Fv = 1029 10-(AB+48.6)/2.5

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