From cosmic ray physics to cosmic ray astronomy: Bruno Rossi and the opening of new windows on the universe

TL;DR

Bruno Rossi's pioneering work in cosmic ray physics and space-based observations laid the foundation for modern high-energy astrophysics and X-ray astronomy, opening new observational windows on the universe.

Contribution

The paper highlights Rossi's innovative approach in leveraging new technological windows, such as space-based measurements, to advance cosmic ray research and establish X-ray astronomy.

Findings

First in situ measurements of solar wind at Earth's magnetosphere boundary.

Discovery of Scorpius X-1, the first extra-solar X-ray source.

Pioneering the transition from cosmic ray physics to space-based astrophysics.

Abstract

Bruno Rossi is considered one of the fathers of modern physics, being also a pioneer in virtually every aspect of what is today called high-energy astrophysics. At the beginning of 1930s he was the pioneer of cosmic ray research in Italy, and, as one of the leading actors in the study of the nature and behavior of the cosmic radiation, he witnessed the birth of particle physics and was one of the main investigators in this fields for many years. While cosmic ray physics moved more and more towards astrophysics, Rossi continued to be one of the inspirers of this line of research. When outer space became a reality, he did not hesitate to leap into this new scientific dimension. Rossi's intuition on the importance of exploiting new technological windows to look at the universe with new eyes, is a fundamental key to understand the profound unity which guided his scientific research path up to its culminating moments at the beginning of 1960s, when his group at MIT performed the first in situ measurements of the density, speed and direction of the solar wind at the boundary of Earth's magnetosphere, and when he promoted the search for extra-solar sources of X rays. A visionary idea which eventually led to the breakthrough experiment which discovered Scorpius X-1 in 1962, and inaugurated X-ray astronomy.