Scattered dots of light can tell us a lot! If you find a photon of a frequency that's only produced by, say, a CO2 molecule, you can prove that CO2 existed 50 million years ago. Ok wow, probably not too useful. Collect a bunch of photons, count how many indicate CO2 and how many indicate O2, and you can figure out the composition of Earth's atmosphere. All of this using single photon detections!

Theoretically you'd just need an enormous telescope to collect enough light to resolve an image. Though based on the features that modern telescopes can resolve on the moon ~1 light second away, it'd probably need a telescope on the scale of a galaxy