I wonder if a cluster of stars can be treated as a MIMO scattering channel for more distant unknown objects? If so, it should be possible to resolve details in the unknown object. I guess the geometry would have to be such that there is appreciable signal from each star/scatterer (ie. sort of colinear), but there would be no requirement to be on a focal line?
One of the first James Webb Space Telescope pictures is a picture of a massive galaxy cluster that causes visible gravitational lensing, which produces distorted images from highly redshifted galaxies behind it. Seems our galaxy cluster is located in its focal point.
I guess one problem could be that the scatterers/stars are luminous, so their own emissions might overpower the scattered signal? Maybe a cluster of darker objects? Or maybe luminous objects are okay if the scattered waves are coming from dark regions surrounding the scatterers and have enough angular separation that they can be resolved from the scatterer's own emissions?
hmm.. right.. if the angle of deflection is low and the star is close enough that its light and deflected light show up very close together. My intuition is this is not the case... remember Eddington's test of relativity was for deflection of starlight around our Sun. We're really close, yet it was observable with the moon obscuring the main sunlight.
the article[1] says "For light grazing the surface of the sun, the approximate angular deflection is roughly 1.75 arcseconds." So, what, we take the arcsin of 1.75 arcseconds to get the apparent divergence ratio, and multiply that by distance to stars? As long as that value is larger than the aperture of your camera, then you don't get competing light? Or maybe you'd need something like the TESS satellite, where you have a screen specially created to only allow certain beam transits into your detector.
I've worked with a nearest 10k stars database (https://celestiary.github.io/, zoom way out) and the edge of that is about 2k light years away. So very roughly, let's say there's 1/8th of those in a certain direction... so you get.. what? some 2k sample points towards some distant object? But really most of them wouldn't deflect that object's light towards Earth, but usually over or undershoot.
Don't really know how to put these together quickly, but is giving me some good food for thought!
Also thinking about channel sounding. MIMO usually has a method of measuring the channel response with known data (or a known property of the data, such as a modulation type), then the channel is either assumed to be stationary whist the unknown data is sent, or a model is used to extrapolate the channel response.
I wonder if the star around which the exoplanet orbits can be used to sound the channel? The light from the star would contain information in the form of its spectra. Maybe this can be used to get the channel response? Perhaps the spectra can be treated as a form of modulation?
Maybe related, depending on how close the light from the far target is to tangent near the lensing star, there is also an atmosphere around the star that is emissive. I was thinking that's mostly noise, but maybe it's accelerated enough to shift its spectrum and serve some purpose in measuring the lensing strength? But either way, would need to characterize it enough to remove it from signal.
Heya, I'm really inspired by the idea. I propose we work it up into a paper, On the Existence (or not) of a Multiple Gravitational Lens Telescope.
I've created a project under Celestiary since I think we can use the code there to do the search on the Celestia star database and also do simulations.
