Sunday, March 9, 2014
Fabricius is most remembered for being the first to observe a variable star, the variable star later named Mira. A variable star is a star whose brightness, as observed from earth, changes over time. Fabricus first observed the variable star in 1596 and watched it first brighten and then disappear over the course of three weeks. At first Fabricus believed he had observed a nova (a dying star, which shines brightly then disappears) but when the star reappeared he realized that it was a star that changed it's brightness over time. This observation was largely forgotten until the mid 1600s when it was rediscovered by Polish astronomer Johannes Hevelius and French astronomer Ismail Bouillaud. It was Bouillaud who determined that the star had a period of 333 days. The fact that there was an star that changed it's brightness over time was revolutionary and contradicted the Aristotelian idea that the heavens are unchanging that was church doctrine at the time.
Fabricius' oldest son, Johannes, was also an astronomer and the pair used a camera obscura so that they could observe the sun and were the first to publish the existence of sunspots. From his observations Fabricus correctly predicted the axial rotation of the sun. Fabricus corresponded with Tycho Brahe and Johannes Kepler. Kepler used some of Fabricius observations of Mars in constructing his model of the solar system with the sun at the center and the planets orbiting it in elliptical orbits. Fabricius never believed in this model and instead he believed in the Tychoean model with the planets orbiting the sun and the sun, as well as all the stars, orbiting the Earth.
Fabricius was killed on May 7, 1617, by a shovel-wielding parishioner whom he had accused of stealing a goose.
Boner, Patrick J.; "David Fabricius"; in Biographical Encyclopedia of Astronomers; Springer; 2007
Granada, Miguel A.; "Johannes Kepler and David Fabricius: Their Discussion of the Nova of 1604"; in Change and Continuity in Early Modern Cosmology; Patrick J. Boner, Editor; Springer; 2011
Shiga, David; "Astrophile: The Rebel Star that Broke the Medieval Sky"; New Scientist; October 14, 2011
David Fabricius Wikipedia Entry