16 December

1826: Giovanni Battista Donati was born.

Donati was an Italian astronomer who, on 5 August 1864, was the first to observe the spectrum of a comet (Comet 1864 II). This observation indicated correctly that comet tails contain luminous gas and do not shine merely by reflected sunlight.

He also discovered the comet now known as Donati's Comet at Florence on 2 June 1858.