Russian-born American astronomer who with B. Gerasimovic demonstrated the pervasiveness of interstellar matter (1929). This discovery was significant for attempts to map stellar distribution, because intersellar matter distorts starlight by absorption. Struve later discovered the presence of interstellar hydrogen, a result crucial for radio astronomy. He was director of both Yerkes Observatory (1932-1947) and McDonald Observatory (1939-1947), which he was instrumental in founding. Struve was awarded the Royal Astronomical Society's Gold Medal in 1944.