Sagittarius A* - the black hole at the centre of the Milky Way

Assembled from 26 blocks · 3 evidence · 16 related

1. Story
2. The compact radio source at the dynamical centre of our own galaxy, about 8.3 kiloparsecs away, whose mass of roughly four million solar masses is known more securely than that of any other black hole because individual stars have been tracked around it for three decades. The Event Horizon Telescope published an image on 12 May 2022 showing a ring about 51.8 microarcseconds across, in close agreement with the size the stellar-orbit mass predicts - two entirely independent methods, one Newtonian celestial mechanics applied to stars, one general-relativistic light bending, converging on the same object. It was much harder to image than M87* despite being far closer, because its far smaller mass means the material orbits in minutes rather than days, so the source changes during the observation. Getting an image at all required averaging over many reconstructions and treating the variability explicitly. It is also extremely faint for its mass, accreting at a tiny fraction of the Eddington rate. Not a place on Earth.
3. Knowledge
4. M87* - the supermassive black hole in Messier 87
5. Sagittarius A* - the black hole at the centre of the Milky Way
6. Connections
7. M87* - the supermassive black hole in Messier 87
8. S2 - the star that measured the Galactic centre
9. A star is tracked through a complete close approach to the Galactic centre
10. The Event Horizon Telescope observes M87* and Sagittarius A*
11. S2 passes pericentre and its light is measurably redshifted
12. The orbit of S2 is shown to precess as general relativity predicts
13. The Nobel Prize in Physics recognises black holes twice over
14. The black hole at the centre of our own galaxy is imaged
15. Relativistic jet
16. Sagittarius A* - the black hole at the centre of the Milky Way
17. Heber Curtis records a curious straight ray in Messier 87
18. A mechanism for extracting energy from a spinning black hole
19. The Event Horizon Telescope observes M87* and Sagittarius A*
20. The first image of a black hole shadow is published
21. The M87* ring is imaged in polarised light
22. A second epoch shows the ring persists and the bright spot moves
23. Evidence
24. Reports an image of Sagittarius A* with a ring diameter of about 51.8 microarcseconds, consistent with the mass derived from stellar orbits, and describes the variability that made the imaging difficult. V55 VERIFICATION BASIS: not consulted in session; no research tool was available. Volume and article number are from recall and must be checked.
25. Reports the combined gravitational and transverse Doppler shift in S2's spectrum at its 2018 pericentre passage, inconsistent with Newtonian prediction. V55 VERIFICATION BASIS: not consulted in session; no research tool was available. Volume and article number are from recall and must be checked.
26. Reports a complete stellar orbit around the Galactic centre compact source, constraining the enclosed mass within the pericentre distance. V55 VERIFICATION BASIS: not consulted in session; no research tool was available. Title, volume and page are from recall and must be checked; the period is quoted slightly differently in later analyses.