Bruno Rossi was an Italian-American physicist who was a pioneer in the study of cosmic rays. In the 1930s, his experimental investigations of cosmic rays and their interactions with matter laid the foundation for high energy particle physics. Cosmic rays consist of a variety of charged particles, mainly protons and alpha particles, that enter Earth's atmosphere from space at speeds approaching that of light, bombarding atmospheric atoms to produce mesons as well as secondary particles possessing some of the original energy. Rossi was one of the first to use rockets to study cosmic rays above the atmosphere. Finding X-rays from space he became the father of high energy astrophysics, being largely responsible for starting X-ray astronomy, as well as the study of interplanetary plasma.

 

Rossi and his colleagues discovered the first non-solar source of X-rays – Scorpius X-1. In 1996, NASA renamed its X-ray Timing Explorer (XTE) space telescope to honor him (see RXTE).

 

Rossi served as professor of Physics and Professor Emeritus at MIT, and in 1987 was the corecipient of the prestigious Wolf Prize in Physics. The Bruno B. Rossi Prize, awarded annually to a top astrophysicist for achievements in the field, is named in his honor.