Leiden University at the university. The learning and reputation of Jacobus Gronovius, Herman Boerhaave, Tiberius Hemsterhuis and David Ruhnken, among others, enabled Leiden to maintain its reputation for excellence down to the end of the 18th century. At the end of the nineteenth century, Leiden University again became one of Europe's leading universities. At the world’s first university low-temperature laboratory, professor Heike Kamerlingh Onnes achieved temperatures of only one degree above absolute zero of −273 degrees Celsius. In 1908 he was also the first to succeed in liquifying helium and can be credited with the discovery of the superconductivity in metals. The
Heike John Aachen and earned a doctorate in 1987. In the same year she was selected as one of five West German astronaut candidates for the Spacelab D-2 mission, along with Hans Schlegel, Ulrich Walter, Gerhard Thiele and Renate Brümmer. She served as Cap com during the D-2 mission in 1993, but was never assigned to a spaceflight herself. After retiring as an astronaut, she became a professional pilot for Lufthansa. She is married to astronaut Hans Schlegel. Heike John Heike John (now Heike Walpot; born 19 June 1960) is a retired German swimmer and former astronaut candidate. She won a bronze