The cooling speed of white dwarfs suggests a possible new energy-loss channel, consistent with axions if their Yukawa coupling to electrons is 10−13 corresponding to a mass of a few meV. In this case axions provide less than 0.1% of the cosmic cold dark matter, whereas core-collapse supernovae release a large fraction of their energy in the form of axions. These axions would be extremely challenging to detect, but may be accessible to the next generation axion helioscope.