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Johannes Kepler

Johannes Kepler was a scientist and a mathematician from Germany. He made many very important discoveries for astronomy. These included the laws of planetary motion and some improvements to the telescope.

An illustration portrait of Johannes Kepler.


Personal Life

Here’s a fun video about Kepler!


Childhood and Education

Kepler was born in 1571 in Germany. He had a hard time as a child for many reasons. When he was five years old his father left his family. As a child, Kepler often was in poor health. He was born early and was described as “sickly.” He also had smallpox as a child, which affected his vision and his hands. 
Kepler developed a love for astronomy at an early age. When he was six years old, he got to see the Great Comet of 1577. He also saw a lunar eclipse when he was nine years old. 
In 1587, Kepler attended the University of Tübingen. There he studied philosophy and theology, which is the study of religion. His teachers realized that Kepler was also talented at math. In 1594 Kepler became a math and astronomy teacher. 

Marriages and End of Life

In 1597, Kepler married a woman named Barbara Müller. They had two children who sadly died as infants. Later, they had three more children. They were Susanna, Friedrich, and Ludwig. Unfortunately, Kepler’s wife, Barbara, died in 1611.

After Barbara’s death, Kepler got married again. In 1613 he married Susanna Reuttinger. He had six children with her, although the first three died in when they were children. 

In 1630, Kepler got sick and then died in Regensburg, Germany. He was buried in Regensburg. Kepler left an important legacy in astronomy and is a famous scientist to this day. 

An image of Johannes Kepler on a stamp from Germany.

Here is Kepler’s picture on a postal stamp from Germany.

What Did Kepler Discover? 

During his life, Kepler made many big discoveries for astronomy. Here are a few of his most important accomplishments! 

Laws of Planetary Motion 

Between 1609 and 1619 Kepler published his three laws of planetary motion. These laws describe how planets move around the Sun. Here are his three laws: 
  • First Law (Law of Ellipses): Planets orbit the Sun in an elliptical orbit. 

  • Second Law (Law of Equal Areas): A line segment connecting a planet and the Sun will carve out equal areas in equal time

  • Third Law (Law of Harmonies): The period of a planet squared is proportional to the semimajor axis of its orbit cubed

These three laws help astronomers understand outer space. Visit the Kepler’s Laws article to learn more about the laws of planetary motion. 

An illustration of the solar system and planetary orbits.

Kepler made important discoveries about planetary orbits.

Contributions to Heliocentrism 

In 1543, Nicholas Copernicus published his heliocentric theory. This theory stated that the Sun was the center of the Solar System, not the Earth. Many people did not like this theory, especially the Catholic Church. 

When Kepler learned about heliocentrism in school he supported the theory. He spent time defending it against people who doubted Copernicus. 

Today, we can prove that heliocentrism is correct and that the Sun really is the center of the Solar System. 

The Telescope 

In 1608, a German lensmaker named Hans Lippershey invented the first telescope. The next year, Galileo improved on Lippershey design and created his own telescope. He began using it to make important observations about planets in our Solar System. 

Kepler heard about this new invention and began to think of improvements. in 1611, he created a new telescope that had a convex, instead of concave, lens. This telescope worked much better than earlier ones. 

An image of a road safety mirror that bulges outward. This is convex.

Convex things – like this mirror – bulge outward. Concave things bulge inward.

Other Great Resources

Additional Facts about Kepler: https://kids.kiddle.co/Johannes_Kepler

Brief Overview of Kepler as a Scientist: http://www.sciencekids.co.nz/sciencefacts/scientists/johanneskepler.html

Kepler and His Time Period: https://www.famousscientists.org/johannes-kepler/


Written By: Leah Tolby