Cygnus X-1

Assembled from 24 blocks · 1 evidence · 25 related

1. Story
2. The X-ray binary that was for decades the best case that stellar-mass black holes exist. It was found as one of the brightest X-ray sources in the sky in 1964, during the sounding-rocket surveys that opened X-ray astronomy, and became identifiable only when radio observations in 1971 pinned the position precisely enough to match it to the supergiant star HDE 226868. Spectroscopy of that star gave the orbit, the orbit gave a mass function, and the mass function gave a compact companion too heavy to be a neutron star. It is the subject of the most famous wager in the field: Stephen Hawking bet Kip Thorne in 1974 that it was not a black hole, and conceded in 1990. A 2021 analysis combining a new radio parallax distance of about 2.2 kiloparsecs revised the compact object upward to roughly 21 solar masses and inferred a spin close to the maximum the Kerr solution allows. Not a place on Earth.
3. Knowledge
4. Accretion disc
5. Cygnus X-1
6. Stellar-mass black hole
7. Connections
8. Accretion disc
9. Stellar-mass black hole
10. A bright X-ray source is found in Cygnus
11. Cygnus X-1 is localised and weighed
12. Innermost stable circular orbit
13. Relativistic jet
14. Cygnus X-1
15. Cygnus X-1 is localised and weighed
16. Bekenstein assigns entropy to a black hole
17. The first image of a black hole shadow is published
18. The M87* ring is imaged in polarised light
19. A second epoch shows the ring persists and the bright spot moves
20. Cygnus X-1
21. GW150914 - two black holes merge and the signal reaches Earth
22. Supernova
23. Evidence
24. 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.