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Incoming links: X-ray astronomy
Herbert Gursky Created 2026-10-18 Updated 2026-11-05
Herbert Gursky coauthored the 1962 rocket experiment that detected X-rays from beyond the Solar system. Large-area counters carried above the absorbing atmosphere recorded a strong celestial source as well as a more diffuse background.
The payload's changing direction allowed count rate to be compared with sky direction, separating a localized source from broadly distributed counts. The experiment opened X-ray astronomy to objects whose energetic emission could not be measured by ordinary ground-based optical observations.[ref]
Evidence for x Rays From Sources Outside the Solar System by Riccardo Giacconi and others. Author list and pp. 439–443: rocket counters, directional count rates and extrasolar radiation
Riccardo Giacconi Created 2026-10-18 Updated 2026-11-05
Riccardo Giacconi pioneered X-ray astronomy using instruments carried above Earth's absorbing atmosphere. His team's 1962 rocket flight found a strong source outside the Solar system, later known as Scorpius X-1, together with a diffuse X-ray background.[ref]
Evidence for x Rays From Sources Outside the Solar System by Riccardo Giacconi and others. pp. 439–443: rocket-counter observations and directional excess
His Nobel lecture traces the subsequent transition from brief rocket measurements to more sensitive surveys and imaging instruments. Increasing collecting area, observing duration and angular resolving power changed the questions that could be asked: sources could be located, separated and studied as physical systems.[ref]
The Dawn of X-Ray Astronomy by Riccardo Giacconi. Historical account of the first extrasolar X-ray source and development of X-ray observatories
Portrait of Riccardo Giacconi
. ESO; distributed through the International Astronomical Union, image ann18062a. Creative Commons Attribution 4.0 International, as stated for this IAU-distributed image., via Wikimedia Commons. Source.
X-ray astronomy Created 2026-10-18 Updated 2026-10-20
X-ray astronomy infers the properties of celestial sources from their X-rays. It requires instruments above the strongly absorbing layers of Earth's terrestrial atmosphere. Riccardo Giacconi's 2002 Nobel lecture connects the early rocket detections to later grazing-incidence X-ray optics, which collect photons over a large entrance area onto a small detector.[ref]
The Dawn of X-Ray Astronomy by Riccardo Giacconi. The Dawn of X-Ray Astronomy, introduction and section 4, pp. 123–124
The measurement is an inverse problem: a count rate mixes incident photon arrival rate, detector response, and background. A point-like astronomical source produces a direction-dependent excess as the instrument scans; diffuse X-ray background contributes over many directions. Neither a count excess nor a narrow feature by itself determines the emission mechanism. The useful progression is from detecting an excess, to locating it, to measuring its spectrum and light curve.