Arnold Wolfendale conducted research on cosmic rays — immensely energetic particles from sources mainly beyond our Solar System. Arnold became, in particular, a world expert on muons — an elementary particle similar to the electron. His expertise was important in accounting for cosmic ray background effects in experiments that successfully detected neutrinos emitted by nuclear fusion within the Sun.

Arnold developed the neon flash tube and the solid iron spectrograph to improve cosmic ray detection and measurement of their energies. As well as helping us to understand their origin, cosmic ray research has bearing due to the damage that these charged particles can inflict on electronic circuits and living organisms — directly in those sent into space, and indirectly in those on Earth through secondary radiation.

Arnold’s eminence was recognised in his appointment as Astronomer Royal in 1991. He served as President of both the European Physical Society and the Royal Astronomical Society. He was knighted for services to astronomy in 1995.

Sir Arnold Wolfensdale FRS died on 21 December 2020.

Biographical Memoir