Jupiter becomes a telescopic puzzle

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.

The 1604 outburst furnished another striking challenge to the doctrine of immutable heavens.

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

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.

The observation provided a direct test of a calculated planetary transit.

The apparent size of Mercury on the Sun surprised observers and helped refine ideas about its dimensions.