Uhuru

Uhuru was the first satellite dedicated to X-ray astronomy. Launched in 1970, it conducted the first comprehensive survey of the sky in cosmic X-rays.

Proportional counter: A gas-filled detector that measures ionizing radiation by amplifying the charge produced by each event. Uhuru used proportional counters to detect and measure incoming X-rays.
Scorpius X-1: A bright X-ray binary system and the first extrasolar X-ray source discovered. Uhuru measured this prominent source as part of its all-sky survey.
Riccardo Giacconi: An Italian-American astrophysicist whose work helped establish experimental X-ray astronomy. He led the team that developed Uhuru and analyzed its survey.
Uhuru catalog: A catalog of cosmic X-ray sources compiled from Uhuru satellite observations. It provided a lasting record of the mission's all-sky detections.
X-ray astronomy: The study of astronomical objects and phenomena through the X-rays they emit. Uhuru's instruments and survey helped establish this field.
Cygnus X-1: A binary star system containing a black hole and a strong source of X-rays. Uhuru observations helped establish its importance as a compact X-ray source.
NASA Small Astronomy Satellite: A NASA series of small scientific spacecraft designed for focused astronomical observations. Uhuru was the second spacecraft in this satellite series.
Black hole: A region of spacetime whose gravity prevents anything, including light, from escaping beyond its event horizon. Uhuru data strengthened the case that some bright X-ray binaries contain black holes.
Ariel 5: A British X-ray astronomy satellite launched in 1974 that studied cosmic X-ray sources. It extended satellite observations of the X-ray sky after Uhuru.
X-ray binary: A binary star system in which matter falling onto a compact object produces X-rays. Many sources catalogued by Uhuru belong to this class.

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