jansky (Jy)

A jansky (Jy) is the unit used by astronomers for measuring the radio flux density from radio sources; it was named in 1973 by the International Astronomical Union in honor of Karl Jansky. It equals 10-26 watts per square meter per hertz. Pitifully small though this seems, it measures extraordinary small quantities. Were you to use all the energy ever collected from cosmic radio sources to heat a single cup of coffee, you would still have a cold drink.