Hendrik C. van de Hulst
Dutch astronomer
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Hendrik Christoffel "Henk" van de Hulst was a Dutch astronomer.
In 1944, while a student in Utrecht, he predicted the existence of the 21 cm hyperfine line of neutral interstellar hydrogen. Wikipedia
Born: November 19, 1918, Utrecht, Netherlands
Died: July 31, 2000 (age 81 years), Leiden, Netherlands