Declaring that I’m an astronomer at social events never fails to cause a sensation. Sat next to a starry-eyed historian at a College dinner last night, he asked: “how do we learn about stars?” as he picked through the salad vegetables on his plate. Starlight which we observe using telescopes, I said, encodes a wealth of information about the star’s temperature, gravity, and chemical makeup. Telescopes collect parcels of light, called photons, like a bucket collects rain. In1610, Galileo used a simple tube with lenses which he called a spyglass to observe the sky and collect more light than his eyes could. Telescopes have developed a lot since then….