Karl Schwarzschild


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Germanastronomer. He established a method for determining a star's brightness from photographs, comparing its visual and photographic magnitudes to obtain the colour index. In 1905 he obtained ultraviolet photographs of a solar eclipse, and went on to study energy transfer in the Sun, deducing that its outer regions had a layered structure. In 1916 he showed that, in the general theory of relativity, a sphere of material (approximating to a star) collapsing under its own gravitational field past its Schwarzschild radius would cease to radiate energy (i.e. it would become a black hole). His son, Martin Schwarzschild (1912–97), became a naturalized American and studied stellar evolution.

Subjects: Astronomy and Astrophysics.

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