Scorpius X-1

Scorpius X-1 is a low-mass X-ray binary in the constellation Scorpius, where a neutron star accretes matter from a companion star. It was the first extrasolar X-ray source discovered.

Accretion disk: A rotating structure of gas and dust that spirals toward a central object under gravity. Gas transferred from Scorpius X-1’s companion forms a disk before reaching the neutron star.
Aerobee rocket: A family of sounding rockets used to carry scientific instruments above much of Earth’s atmosphere. An Aerobee rocket carried the detector that found Scorpius X-1 in 1962.
X-ray timing: The study of how an astronomical source’s X-ray brightness varies over time. Variability in Scorpius X-1 helps probe changing conditions near its neutron star.
Cygnus X-1: A high-mass X-ray binary in which a black hole accretes matter from a massive companion star. It contrasts with Scorpius X-1 in both compact-object type and companion-star mass.
Roche-lobe overflow: Mass transfer that occurs when a star expands beyond the gravitational region in which it can retain its gas. This process is thought to feed matter from the companion into Scorpius X-1.
Riccardo Giacconi: An Italian-American astrophysicist who helped pioneer observational X-ray astronomy. Giacconi led the team that discovered Scorpius X-1 in an early rocket experiment.
X-ray spectroscopy: The analysis of an X-ray source’s energy spectrum to infer its physical conditions and composition. Its bright emission allows detailed study of the hot gas around the neutron star.
Aquila X-1: A transient low-mass X-ray binary containing a neutron star that alternates between bright outbursts and faint periods. Its episodic outbursts contrast with Scorpius X-1’s persistent bright X-ray emission.
Neutron star: A compact stellar remnant composed mostly of densely packed neutrons, formed in some supernova explosions. The compact object at Scorpius X-1’s center is a neutron star.
X-ray astronomy: The study of astronomical objects and processes through their X-ray emissions. Scorpius X-1’s detection showed that cosmic X-ray sources could be studied from space.

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