Arno Penzias obituary

US astrophysicist whose discovery of the cosmic microwave radiation resulting from the big bang brought him the Nobel prize

The American astrophysicist and Nobel laureate Arno Penzias, who has died aged 90, was responsible for one of the biggest cosmological revelations of the 20th century - the discovery of cosmic microwave background, the leftover radiation from the big bang.

He first demonstrated its existence in 1965 with his collaborator Robert Wilson, and then, five years later - with Wilson and another astrophysicist, Keith Jefferts - went on to detect the presence of interstellar carbon monoxide, launching the field of molecular line astronomy.