Paranal Observatory and the GRAVITY interferometer

Assembled from 17 blocks · 2 evidence · 10 related

1. Story
2. The European Southern Observatory site on Cerro Paranal in the Atacama Desert, whose four 8.2-metre Unit Telescopes can be combined interferometrically. The GRAVITY beam combiner, which links all four, delivers infrared astrometry at the level of tens of microarcseconds - precise enough to follow individual stars around Sagittarius A* through their closest approaches. That capability produced two of the strongest tests of general relativity in a strong field: the detection of the gravitational redshift in the light of the star S2 at its 2018 pericentre passage, and the detection in 2020 of the Schwarzschild precession of S2's orbit, an effect of the same kind as the anomalous precession of Mercury but far larger. The instrument works by measuring the star's position relative to the black hole's own faint infrared emission, so it measures the orbit directly rather than inferring it.
3. Knowledge
4. Paranal Observatory and the GRAVITY interferometer
5. S2 passes pericentre and its light is measurably redshifted
6. Connections
7. S2 passes pericentre and its light is measurably redshifted
8. S2 passes pericentre and its light is measurably redshifted
9. The orbit of S2 is shown to precess as general relativity predicts
10. Paranal Observatory and the GRAVITY interferometer
11. Time dilation near a horizon
12. S2 - the star that measured the Galactic centre
13. Sagittarius A* - the black hole at the centre of the Milky Way
14. Paranal Observatory and the GRAVITY interferometer
15. Evidence
16. 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.
17. 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.