Liquid helium of liquid water. Helium was first liquefied on July 10, 1908, by the Dutch physicist Heike Kamerlingh Onnes at the University of Leiden in the Netherlands. At that time, helium-3 was unknown because the mass spectrometer had not yet been invented. In more recent decades, liquid helium has been used as a cryogenic refrigerant, and liquid helium is produced commercially for use in superconducting magnets such as those used in magnetic resonance imaging (MRI), nuclear magnetic resonance (NMR), Magnetoencephalography (MEG), and experiments in physics, such as low temperature Mössbauer spectroscopy. The temperature required to produce liquid helium is low because
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