Telescopes are time machines, allowing us to experience the universe as it existed long before humans arrived.
The Deer Lick group of galaxies at top right is anchored by NGC 7331, a spiral galaxy 40 million light years away that’s almost identical to the Milky Way in composition, shape, and mass, with a similarly-sized supermassive black hole at its core. Photons from that galaxy traveled at 300 million kilometers per hour for 40 million years through the vacuum of space before intersecting our Milky Way galaxy, our solar system, the Earth, and my telescope. Their journey started 25 million years after an asteroid struck Earth 66 million years ago, causing the extinction of all non-avian dinosaurs.
But the galaxies above NGC 7331, called “the fleas”, and most of the galaxies in the cluster at bottom left are much further away – about 265 million light years distant. Those very old photons were emitted 25 million years before dinosaurs started to evolve from ancestral reptiles called archosaurs to begin their 175-million-year dominion over our planet.
