The system was first noted as
Nova Cygni 1938 and given the
variable star designation V404 Cygni. It was considered to be an ordinary "moderately fast" nova although large fluctuations were noted during the decline. It was discovered after maximum light, and the photographic magnitude range was measured at 12.5–20.5. On May 22, 1989 the Japanese
Ginga Team discovered a new X-ray source that was catalogued as
GS 2023+338. This source was quickly linked to V404 Cygni, which was discovered to be in outburst again as
Nova Cygni 1989. Follow-up studies showed a previously unnoticed outburst in 1956. There was also a possible brightening in 1979. In 2009, the black hole in the V404 Cygni system became the first black hole to have an accurate
parallax measurement for its distance from the
Solar System. Measured by
very-long-baseline interferometry using the
High Sensitivity Array, the distance is , or
light-years. In April 2019, astronomers announced that jets of particles shooting from the black hole were wobbling back and forth on the order of a few minutes, something that had never before been seen in the particle jets streaming from a black hole. Astronomers believe that the wobble is caused by the
Lense-Thirring effect due to warping of space/time by the huge gravitational field in the vicinity of the black hole. In April 2024, astronomers announced that V404 Cygni was discovered to be part of a hierarchical
triple star system, with the tertiary companion being at least 3500
AU away from the inner binary system. This discovery was evidence that V404 Cygni formed with a minimal
black hole natal kick on the order of less than 5 km/s. The tertiary component was also found to be evolved, indicating that the triple system has remained bounded through the black hole's formation and that the system's age is constrained to between 3-5 billion years old. ==2015 outburst==