“Then felt I like some watcher of the skies
When a new planet swims into his ken;…”
“On First Looking into Chapman’s Homer” 
by English poet John Keats (1795–1821).
A timeline of the discovery of the Solar System planets:
By ~ 2000 BC: Ancient Babylonian astronomers had identified the planets Mercury, Venus, Mars, Jupiter and Saturn.
The planet Uranus was discovered in 1781; Neptune in 1851, and Pluto in 1930.
Watchers of the skies:
from various sources, and a fascinating biography of
Johannes Kepler (1571 – 1630), a German mathematician and astronomer; one of three eminent astronomers in the 17th century.
“Kepler’s Witch: An Astronomer’s Discovery of Cosmic Order Amid Religious War, Political Intrigue, and the Heresy Trial of His Mother.”
by James A. Connor; [c] 2004; [ebook edition 2008].
Johannes Kepler (1571 – 1630), a German mathematician and astronomer, was one of three eminent astronomers in the 17th century. He was a contemporary of Galileo Galilei, and Tycho Brahe.
Their observations and scientific works led to fundamental changes in our understanding of the solar system and the Universe.
Kepler’s fundamental discovery was that the orbits of planets around the sun are elliptical and not circular. His planetary laws of motion were key to Isaac Newton’s theory of universal gravitation.
Kepler lived in times often marked by intense religious and political conflicts in Germany, Austria and Bohemia (Prague).
Connor ‘s biography of Kepler is based on translations of letters and journals, and the title refers to the witchcraft and heresy trial of Kepler’s mother Katherina.
Using letters to introduce each chapter, Connor provides depth, and insight, into how Kepler lived and worked even when his own life was caught up in the religious and political turmoil of his times.
Kepler was a Lutheran, and worked as mathematician and astronomer in the principalities of German, Austrian, and Bohemian dukes and emperors. Kepler himself experienced significant turmoil and upheaval in his life, as a result of the conflicts of the Reformation – Counter-reformation movements, and the Thirty Years’ War in Europe from 1618 and 1648.
Kepler lived in Prague, from 1600 to 1612. He was initially assistant to the astronomer Tycho Brahe who was the imperial mathematician to Emperor Rudolf II. In 1601, after the death of Tycho Brahe, Kepler was appointed imperial mathematician to Emperor Rudolph II, and continued to serve also Rudolf’s successors Matthias and Ferdinand II.
Kepler was widowed twice; he was devoted to his family and his personal sorrows were marked by the loss of some of his children to illnesses. Kepler and his family left Prague in 1612 to live in Linz.
In 1617, his mother Katherina was accused of witchcraft and heresy, in her hometown of Leonberg. Kepler sought extensive legal help and wrote letters in support of his mother’s innocence. But Katherina was convicted and imprisoned. Kepler continued his legal efforts to have her released, and Katherina was finally released in 1621.
In his later years, in 1626, amidst rising political and religious tensions, Kepler and his family moved to Ulm, and finally to Regensburg. Kepler died in Regensburg in 1630.
Throughout his life, Kepler continued with his scientific works, including their publication. His writings show that he had a strong faith in God, and he kept that belief at the center of his life and scientific works. He was unwavering in his belief that religion ultimately is between an individual’s conscience and God. Kepler remained a Lutheran although he was excommunicated by his own church.