Very long baseline interferometry

Assembled from 10 blocks · 1 evidence · 8 related

1. Story
2. The technique that lets telescopes thousands of kilometres apart behave as one. Each station records the incoming radio signal with a timestamp from a hydrogen maser clock, and the recordings are later combined so that the interference between pairs of stations is recovered; the angular resolution is set by the separation between stations rather than by the size of any dish. No signal passes between the telescopes while they observe. The essential limitation is that such an array samples only a sparse set of points in the plane of spatial frequencies, so most of the information a filled aperture would collect is simply absent, and an image must be reconstructed by choosing among the many pictures consistent with the data. That is why the phrase "photograph of a black hole" is misleading: what is published is a reconstruction, and the discipline of the field is in demonstrating that the chosen reconstruction is not an artefact of the choosing. Not a place on Earth.
3. Knowledge
4. Very long baseline interferometry
5. Connections
6. Event Horizon Telescope
7. The Event Horizon Telescope observes M87* and Sagittarius A*
8. The first image of a black hole shadow is published
9. Evidence
10. Reports the first image of a black hole shadow, an asymmetric ring about 42 microarcseconds across, together with the array, observing campaign and imaging methodology. V55 VERIFICATION BASIS: not consulted in session; WebFetch to iopscience.iop.org and eventhorizontelescope.org was refused by the egress proxy and no search could be issued. Volume and article number are from recall of a canonical citation.