Tycho Brahe on the comet of 1577. 17th-century diagram of the orbit of the comet of 1577 within the solar system, as described by Danish astronomer Tycho Brahe (1546-1601). The diagram also shows the Tychonic system that Tycho devised to account for his observations of the comet's orbit. The Sun and Moon orbit the Earth (centre), while the planets (Mercury and Venus shown here) and the comet orbit the Sun. The Great Comet of 1577 was so bright that it was visible during daylight. This page is from the 1603 edition of Tycho's 'De Mundi Aetherei Recentioribus Phaenomenis Liber Secundus', originally published in 1588.