If we could somehow glance down at the entire Milky Way, our home galaxy would look like a spinning pinwheel. In it, some 100 I billion stars are sprinkled across 100,000 light years, accompanied by unfathomable amounts of gas and dust. Together, these galactic components swirl around in a stellar disc, spilling into four giant spiral arms emanating from the galaxy’s blinding centre, the home of a supermassive black hole.
We’ve come to really identify our galaxy with its spiral structure, although its exact number of galactic arms is still being debated. Yet astronomers have long puzzled over
