Johann(es) Fabricius (8 January 1587 – 19 March 1616), eldest son of David Fabricius (1564–1617), was a Frisian/German astronomer and a discoverer of sunspots (in 1610), independently of Galileo Galilei.
Johannes was born in Resterhafe (East Friesland). He studied at the University of Helmstedt, Wittenberg University and graduated from Leiden University in 1611. He returned from university in the Netherlands with telescopes that he and his father turned on the Sun. Despite the difficulties of observing the sun directly, they noted the existence of sunspots, the first confirmed instance of their observation (though unclear statements in East Asian annals suggest that Chinese astronomers may have discovered them with the naked eye previously, and Fabricius may have noticed them himself without a telescope a few years before). Johannes first observed a sunspot on February 27, 1611; in Wittenberg that year he published the results of his observations in his 22 page pamphlet De Maculis in Sole observatis.....
The pair soon used camera obscura telescopy so as to save their eyes and get a better view of the solar disk, and observed that the spots moved. They would appear on the eastern edge of the disk, steadily move to the western edge, disappear, then reappear at the east again after the passage of the same amount of time that it had taken for it to cross the disk in the first place.
Copies of a map he made of Frisia in 1589 are also still extant. He is also name-checked in Jules Verne's From the Earth to the Moon as someone who claimed to have seen lunar inhabitants through his telescope, though that particular fact is merely part of Verne's fiction. The large (90-kilometre or 56-mile) Fabricius crater, on the Moon's southern hemisphere, is named after his father, David Fabricius.
He died in Marienhafe, at the age of 29.
In 1895, a monument was erected to his memory in the churchyard at Osteel, where he had been pastor from 1603 until 1616.
- Joh. Fabricii Phrysii De Maculis in Sole observatis, et apparente earum cum Sole conversione, Narratio, etc. Witebergae, Anno M.DC.XI. (year 1611).
- Gerhard Berthold: Der Magister Johann Fabricius und die Sonnenflecken, nebst einem Excurs über David Fabricius (Magister Johann Fabricius and Sunspots, together with a Digression on David Fabricius), Leipzig, 1894.
- L. Häpke: "Fabricius und die Entdeckung der Sonnenflecken" ("Fabricius and the Discovery of Sunspots") in: Abhandlungen des naturwissenschaftlichen Vereins zu Bremen, 10, 1888, pp. 249–272.
- Bunte: "Über Johannes Fabricus, den Entdecker der Sonnenflecken" ("On Johannes Fabricius, the Discoverer of Sunspots") in: Jahrbuch der Ges. für bildende Kunst und vaterländ. Altertümer zu Emden 9, H. 1, 1890, pp. 59–77.
- Diedrich Wattenberg: David Fabricius. Der Astronom Ostfrieslands (David Fabricius. Astronomer of East Friesland), Berlin 1964.
- Fritz Krafft: in Walther Killy's Literaturlexikon: Autoren und Werke deutscher Sprache (Literature-Lexicon: Authors and Words of German Language), 15 volumes, Gütersloh; München: Bertelsmann-Lexikon-Verl. 1988-1991 (CD-ROM Berlin 1998 ISBN 3-932544-13-7), Vol. 3.
- Wilfried Schroeder, The Discovery of Sunspots, Bremen 2009
- Willy Jahn (1959) (in German). "Neue Deutsche Biographie (NDB). 4. Berlin: Duncker & Humblot. pp. 732. ". In
- Based on text in main reference.
- Hockey, Thomas (2009). The Biographical Encyclopedia of Astronomers. Springer Publishing. ISBN 978-0-387-31022-0. Retrieved August 22, 2012.
- C., Thony. "Spotting the spots.". Retrieved 17 January 2011.
- Wilfried Schroeder has published the paper by Fabricius on the discovery of sunspots in 1611 in the book , Wilfried Schroeder, The discovery of sunspots, Bremen 2009
- This article incorporates text from a publication now in the public domain: Gilman, D. C.; Thurston, H. T.; Moore, F., eds. (1905). "article name needed". New International Encyclopedia (1st ed.). New York: Dodd, Mead.
- The Galileo Project — biography of David and Johannes Fabricius.
- Eintrag im Biographischen Lexikon für Ostfriesland