Kepler

J. Kepler, astronomer and mathematician, made a study of planets and their movements.

The smaller planets hovering around the planet Jupiter reminded him of the guards surrounding a king when he walked outdoors, and Kepler called them satellites.

Tycho's painstakingly collected data was reduced by Kepler to become grist for the mill that ground out Newton's gravitational theory.

In 1600, Tycho Brahe hired Johannes Kepler as his assistant. In later years, Kepler would use Brahe's work as the basis for the laws of planetary movement which he developed.

Brahe died in 1601. His last words, "Ne frusta vixisse vidar" (may I not seem to have lived in vain), were recorded by his assistant Kepler.

Another step forward in the search for extrasolar planets began with the launch in 2009 of the Kepler space observatory, NASA's first extrasolar mission. Kepler's goal was to search hundreds of thousands of stars for signs of planets.

Kepler has found a diverse array of planets, including exotic, multi-planet solar systems.

Kepler has found that smaller planets (Earth-sized rather than Jupiter-sized) are likely to be the most common in the Milky Way galaxy.

Kepler uncovered several planets that are about the same size as Earth and orbit within the star's habitable zone, where liquid water, which is necessary for life, can exist.

Overall, Kepler has added more than 1,200 confirmed planets to the extrasolar planet count, which now stands at nearly 3,700.