Gamma-ray astrophysics: roots, growth, and success

Gottfried Kanbach

doi:10.1007/s12210-019-00793-w

Abstract

This short review outlines the historic roots of high-energy astronomy in the early twentieth century with the discovery of radioactivity, cosmic ray research, and the development of detectors to measure high-energy photons. The beginning of the space age in the 1960s provided the means to observe cosmic gamma rays unhindered by the absorption and local background inside Earth’s atmosphere. We describe the results from pioneering missions in the 1970s up to the first ‘golden age’ of gamma-ray astronomy in the 1990s with the Compton Gamma-Ray Observatory (CGRO). The focus in this review will be on gamma-ray astronomy in the pair creation energy band, above several 10’s of MeV.

Highlights

High-energy astrophysics, as we know it today, is based on two fundamental discoveries that were made around the early twentieth century: radioactivity and the first classification of subatomic particles as, and radiation (Becquerel 1896; Rutherford 1899; Villard 1900), and cosmic rays measured as ‘radiation of great penetrating power entering our atmosphere from above ...’ (Hess 1912)
As it turned out the ‘cosmic radiation’ observed at balloon altitudes was mostly secondary to a very high-energy flux of primary cosmic rays
Measurements performed on balloons and sounding rockets made clear that cosmic rays consisted of ∼ 99% of protons and nuclei

Summary

Introduction

High-energy astrophysics, as we know it today, is based on two fundamental discoveries that were made around the early twentieth century: radioactivity and the first classification of subatomic particles as , , and radiation (Becquerel 1896; Rutherford 1899; Villard 1900), and cosmic rays measured as ‘radiation of great penetrating power entering our atmosphere from above ...’ (Hess 1912). As it turned out the ‘cosmic radiation’ observed at balloon altitudes was mostly secondary to a very high-energy flux of primary cosmic rays. Atmospheric e-m showers & Čerenkov emission (> 20 GeV): Large ground based telescopes with ultra-fast photon detectors

The roots of gamma‐ray astrophysics: before 1960

Findings

Compliance with ethical standards