Arno A. Penzias, whose astronomical probes confirmed what became known as the Big Bang theory, died on Jan. 22 in San Francisco. He was 90.

Dr. Penzias shared the 1978 Novel Prize in physics with Robert Woodrow Wilson for their discovery in 1964 of cosmic microwave background radiation, remnants of an explosion that gave birth to the universe some 14 billion years ago, now the accepted explanation for the origin of the universe.

Dr. Penzias was born in Munich in 1932. In 1939, he and his brother, Gunter, were put on a train as part of the Kindertransport, the British rescue effort that brought some 10,000 children to England. The family reunited in New York in 1940.

Dr. Penzias’s path to stumbling onto the answer to one of humanity’s most central questions started when he joined Bell Laboratories as a member of its radio research group in Holmdel. There he saw the potential of AT&T’s new satellite communications antenna, a giant radio telescope known as the Holmdel Horn, as a tool for cosmological observation.