Cornelius (or Cornelio) Gemma (February 28, 1535 - October 12, 1578) was a Belgian physician, astronomer and astrologer, and the oldest son of cartographer and instrument maker Gemma Frisius. As an astronomer, he is significant for his observations of a lunar eclipse in 1569 and of the 1572 supernova appearing in Cassiopeia, which he recorded on November 9, two days before Tycho Brahe. With Brahe, he was one of the few astronomers to identify the Great Comet of 1577 as superlunary. He is also credited with publishing the first scientific illustration of the aurora, in his 1575 book on the supernova. Another milestone appears in his medical writings: in 1552, Gemma published the first illustration of a human tapeworm. His two major works, De arte cyclognomica (1569) and De naturae divinis characterismis (1575), have been called, true hidden gems, in early modern intellectual history. He died in 1578, at the age of 43, in an epidemic of the plague. This image has been color enhanced.