Jacobus Cornelius Kapteyn


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Dutchastronomer. He developed statistical methods for reducing and handling large amounts of observational data. Kapteyn compiled the Cape Photographic Durchmusterung, a catalogue of southern stars, from photographs taken in South Africa by D. Gill. A programme of measuring proper motions (which turned up Kapteyn's Star in 1897) revealed two preferred directions of motion (star streams), a result of the rotation of the Galaxy. In 1906 he began his plan of measuring the positions and brightnesses of stars in 206 areas distributed regularly over the sky (the Kapteyn Selected Areas). With his compatriot Pieter Johannes van Rhijn (1886–1960), Kapteyn attempted to estimate the size and shape of the Galaxy. However, he wrongly concluded that the Sun lay near the centre of the Galaxy, being unable to gauge correctly the effect of interstellar absorption which obscures the Galaxy's true extent.

Subjects: Astronomy and Astrophysics.

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