What was Christian Doppler's middle name?

Christian Doppler’s middle name was Andreas.

Doppler was born in Salzburg on November 29, 1803, and baptismal records identify him as Christianus Andreas Dopler. Modern biographies generally render this as Christian Andreas Doppler. He became an Austrian mathematician and physicist whose work established the principle now called the Doppler effect: an observed wave frequency changes when the source and observer move relative to one another.

Doppler presented his landmark idea in 1842 in a paper about the colors of binary stars. He correctly connected motion with changes in observed frequency, although his original attempt to explain stellar colors was not fully correct. The principle was later tested for sound by Christoph Buys Ballot in 1845 and extended to electromagnetic waves by Hippolyte Fizeau in 1848.

A common mix-up is the name “Johann Christian Doppler.” That form was introduced decades after Doppler’s death and is considered a later misnomer; his historical birth and baptismal records support Christian Andreas Doppler.