Does not exist. From an astronomical point of view, no one has observed planets outside the solar system yet, because the stars are too bright and the planets are completely submerged in the brightness of the stars. The so-called observed planets are all inferred by indirect methods. For example, measure the brightness change of a star when a planet passes in front of it. Because planets block some light from stars. Although this change is very small, CCD in modern telescope can accurately detect the change of photon number. Of course, the specific signal amplification process is more complicated. If you are curious, simply put, it is to use a photomultiplier tube (PMT) to achieve gain. Of course, there are other ways to measure it. But don't say so much.

I wrote it myself and hope to adopt it.