A changing sky confronts older cosmology

Tycho's subsequent careful measurements tracked the object's position and brightness; the first sighting was on this date.

The appearance of SN 1572 opened new arguments about celestial change; its physical interpretation came centuries later.

Johannes Kepler observed the bright new star of 1604 in the constellation Ophiuchus.

Kepler's dated observation became part of the record of the last supernova known to have been visible in our Milky Way.

Observers could see this extraordinary object without a telescope; the remnant remains a subject of study.

He recorded three small points near Jupiter, initially regarding them as background stars.

The positions of the lights were unusual enough to prompt repeated observations on later nights.

His first dated observations began the sequence that established satellites orbiting Jupiter.

A more powerful telescope made faint neighboring points visible; recognition of their orbits followed later.

Pierre Gassendi observed Mercury as a tiny dark dot moving across the solar disk.