Hulst, van de, Hendrik Christoffel (1918–2000)

Dutch astronomer who made his most important discovery while still a student. He studied the hydrogen atom and in 1944 predicted that clouds of hydrogen gas in space should emit and absorb a spectral line at wavelength 21 cm/8 in. After this radiation was discovered in 1951, he, Jan H Oort, and C Alex Muller led the Dutch team that mapped the clouds of the Milky Way and delineated its spiral structure.

Van de Hulst has made extensive studies of interstellar grains and their interaction with electromagnetic radiation and has written important books on light scattering and radio astronomy. He has investigated the solar corona and the Earth's atmosphere.

Van de Hulst was born and educated in Utrecht, the Netherlands, and has been based at the University of Leiden since 1946. He has been a leader in many international organizations, especially in space astronomy.