S2 - the star that measured the Galactic centre

Assembled from 24 blocks · 3 evidence · 16 related

1. Story
2. A hot, young star on a highly eccentric sixteen-year orbit around Sagittarius A*, and the single most productive test particle in the study of black holes. At closest approach it passes within roughly 120 astronomical units - on the order of a thousand Schwarzschild radii - and reaches about two and a half per cent of the speed of light. Because the orbit is short enough to be watched in full and close enough for relativistic corrections to be measurable, two decades of infrared astrometry and spectroscopy have used it to weigh the central mass, to confirm that the mass is concentrated within the pericentre distance, and then to detect general-relativistic effects directly: the gravitational redshift of its light at the 2018 pericentre passage, and the Schwarzschild precession of the orbit itself, reported in 2020. Its existence is also a puzzle in its own right, since a massive young star should not easily form so close to a supermassive black hole. Not a place on Earth.
3. Knowledge
4. Sagittarius A* - the black hole at the centre of the Milky Way
5. S2 - the star that measured the Galactic centre
6. Connections
7. Sagittarius A* - the black hole at the centre of the Milky Way
8. A star is tracked through a complete close approach to the Galactic centre
9. S2 passes pericentre and its light is measurably redshifted
10. The orbit of S2 is shown to precess as general relativity predicts
11. The Nobel Prize in Physics recognises black holes twice over
12. The black hole at the centre of our own galaxy is imaged
13. M87* - the supermassive black hole in Messier 87
14. S2 - the star that measured the Galactic centre
15. A star is tracked through a complete close approach to the Galactic centre
16. The Event Horizon Telescope observes M87* and Sagittarius A*
17. S2 passes pericentre and its light is measurably redshifted
18. The orbit of S2 is shown to precess as general relativity predicts
19. The Nobel Prize in Physics recognises black holes twice over
20. The black hole at the centre of our own galaxy is imaged
21. Evidence
22. 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.
23. 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.
24. Reports relativistic pericentre advance in the orbit of S2 at the rate general relativity predicts. V55 VERIFICATION BASIS: not consulted in session; no research tool was available. Volume and article number are from recall and must be checked.