Cygnus X-1 is localised and weighed

Assembled from 23 blocks · 1 evidence · 15 related

1. Story
2. 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.
3. Knowledge
4. Accretion disc
5. Cygnus X-1
6. Cygnus X-1 is localised and weighed
7. Connections
8. Cygnus X-1
9. Accretion disc
10. Accretion disc
11. Stellar-mass black hole
12. A bright X-ray source is found in Cygnus
13. Cygnus X-1 is localised and weighed
14. Innermost stable circular orbit
15. Relativistic jet
16. Cygnus X-1
17. Cygnus X-1 is localised and weighed
18. Bekenstein assigns entropy to a black hole
19. The first image of a black hole shadow is published
20. The M87* ring is imaged in polarised light
21. A second epoch shows the ring persists and the bright spot moves
22. Evidence
23. 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.