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1611 - Sunspots appear in literature
German medical student, Johannes Fabricius, publishes a book titled ‘Narration on Spots Observed on the Sun and their Apparent Rotation with the Sun,’ the first publication on the subject. However, Fabricius was not the first to discover sunspots - records exist of Chinese astronomers noting their existence as early as 800 BC. Sunspots are large cooled areas of the Sun’s photosphere, the causes of which are largely unknown, but they are currently thought to be due to interactions with the Sun’s magnetic field.
1983 - First man-made object to leave the Solar System
Space probe Pioneer 10 crosses Neptune's orbit (then the outermost planet in the Solar System) to become the first man-made object to leave the Solar System. It remained the farthest human-made object in existence until 1998 when it is overtaken by Voyager 1. Equipped with 11 scientific instruments, it was the first spacecraft directed towards interstellar space. The last signal was detected from the spacecraft on 23 January 2003.
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