撒哈拉沙漠上空的仙女星系
2022年7月11日 Andromeda over the Sahara Desert Credit & Copyright: Jordi Coy Explanation: What is the oldest thing you can see? At 2.5 million light years distant, the answer for the unaided eye is the Andromeda galaxy, because its photons are 2.5 million years old when they reach you. Most other apparent denizens of the night sky — stars, clusters, ...