What Did the Milky Way Look Like Before It Was the Milky Way?

I’ve been reading through the papers and notes behind every episode, and members can download those research notes, with every source, on Patreon. If you’d like to read alongside the episodes, they’re waiting for you there. 👉   / thesleepyphysicist1   What did the Milky Way look like before it was the Milky Way? This video goes looking for how our galaxy formed, using the stars that remember it. Short answer: messier than you’d think. The oldest stars born here, a population astronomers call Aurora, barely spin at all as they circle the center, as if the galaxy hadn’t started turning yet when they formed. Then there’s the “poor old heart.” About 18,000 faint, metal-poor stars, picked out in 2022 from two million giants near the galactic center, still drifting where the galaxy began. And the swallowed galaxies, one after another. Shiva and Shakti. Kraken. Heracles, hiding under the dust. Gaia-Sausage-Enceladus, which astronomers are still arguing about (how big it was, and even when it arrived). Some of this is solid. Some of it is very much up for debate, and I’ve tried to be honest about which is which. Near the end, Webb gives us a glimpse of a galaxy like ours at the start: the Firefly Sparkle, ten little clusters of stars, seen 600 million years after the Big Bang. I have to admit, this one was special to make. Of everything I’ve researched for this channel, it’s among the videos I enjoyed most, and I kept finding one more paper I wanted to read. So let it play, low and slow, and drift off somewhere back near the beginning... before anything turned. Timestamps 0:00 Before Anything Turned 6:29 1962, a Single Falling Cloud 11:44 Clusters That Refused a Pattern 16:44 Ten Percent From One Lost Galaxy 22:37 Hidden on the Far Side 27:07 How Old Is a Star? 32:39 Aurora’s Restless Crowd 38:57 The Spin-Up 45:07 The Poor Old Heart 51:23 Weighing What Remains 56:30 Shiva and Shakti 1:02:53 Kraken in the Clusters 1:08:51 Heracles Under the Dust 1:14:40 A Disk at 800 Million Years 1:19:08 The Shape of a Sausage 1:26:11 Four to One, or Eight? 1:32:16 Fuel From the Wreckage 1:37:16 The Splash 1:42:11 Moving Backward 1:46:51 Wrinkles Too Sharp to Be Old 1:52:26 Older Than the Disk It Lives In 1:58:26 One Path Out of Many 2:03:09 When the Bar Formed 2:08:23 A Galaxy Seen at Six Hundred Million Years 2:14:07 Eight Hundred Seventy-Seven Twins 2:18:29 The Last Galaxy Still Falling In 2:24:01 Where the Sun Began 2:28:20 Still Being Written