Cygnus X-1 is localised and weighed
Radio observations in 1971 fixed the position of the X-ray source precisely enough to associate it with the supergiant star HDE 226868. Optical spectroscopy of that star then gave the binary orbit, and the orbit gave a mass function implying an unseen companion too massive to be a neutron star. It was the first object for which the black hole interpretation became the least uncomfortable available, and it remained the standard case for decades.
Historical — it happened, and the record is settled.
Subjects
- Cygnus X-1 · celestial body · Constellation Cygnus, as seen from Earth · not located
- Accretion disc · phenomenon · not located
Evidence
Partly verified — Core facts are sourced; some optional detail is deliberately absent.
Cygnus X-1 contains a 21 solar mass black hole - implications for massive star winds
Revises the distance to Cygnus X-1 by radio parallax and with it the mass of the compact object, to approximately 21 solar masses. V55 VERIFICATION BASIS: not consulted in session; no research tool was available. Title wording, volume and page are from recall and must be checked; the near-maximal spin inference reported alongside is model-dependent.
Science · 2021 · Partly verified
J. C. A. Miller-Jones et al., Science 371, 1046 (2021)
Recorded on Cygnus X-1
Related
Related because they share a subject in the Atlas — never because the text looks similar.