If we were able to send a probe to 550AU from the Sun, which exoplanets could be examined, to what resolution, and what form would the examination take? It is radio telescopy only, or would it be possible to optically see what the surface of an exoplanet looked like?
I've seen this question for the past few days and have shied away from it because it seemed too difficult, but here goes:
550AU is the focal point of the sun, so theoretically anything on the opposite side would be focused into a perfectly coherent image right? Unfortunately due the density of the sun (Mass to radius ratio specifically) only radio waves that just miss the sun would be focused to that point, all other shorter wavelengths don't diffract enough and simply 'collide' with the sun or form a lense ring at a greater distance. So radio-observation only. Explained at this article https://physics.stackexchange.com/a/25501
A star such as a neutron star however would make an excellent candidate for stellar lensing because it has a high density and low radius, meaning much shorter wavelength radiation is able to go around the star.
This wouldn't be particularly effective at discovering new exoplanets, only observing them in more detail.