A Day in Astronomy: Birth of Astronomer Johannes Kepler

Credit: NASA

It was on December 27, 1571 that German astronomer, mathematician, and astrologer Johannes Kepler was born in the Free Imperial City of Weil der Stadt. He is best remembered for his laws of planetary motion, though he had many discoveries, including:

  • The first to formulate eyeglass designing for nearsightedness and farsightedness;
  • The first to explain the principles of how a telescope works;
  • The first to develop integral calculus;
  • The first to explain that the tides are caused by the Moon; and
  • The first to derive the birth year of Christ (a date that is now universally accepted).

Kepler’s name is also attached to a NASA space telescope launched into space in 2009 that was designed to detect exoplanets, which it did with great success. Thanks to the Kepler Space Telescope, we now know that planets are common throughout the galaxy, including Earth-sized planets. As of today, NASA reports there are 5,235 confirmed exoplanets, and more than 9,000 are still being reviewed. However, using the small patch of sky studied by the Kepler telescope as a start, scientists now estimate the Milky Way may contain over 100 billion exoplanets.

Credit: NASA Exoplanet Exploration