Uploads from Dr. Becky

Currently Playing: Did the Milky Way have a merger with another galaxy 12.3 billion years ago?! #shorts

How do you figure out how many mergers the Milky Way has had in its past? Well what Massari et al. (2026) did was look at the speed and properties of 39 globular clusters. And then they then fitted their data with different models that had either 2, 3, or 4 separate populations of globular clusters coming from different merger events in the Milky Way’s past. And their best fit model was 3 distinct groups of star clusters. So the black points all have similar properties and Massari et al. claim these are clusters that have formed within the Milky Way itself. Whereas the cyan points all have similar properties to the Gaia-Sausage-Enceladus. But there’s also a separate group shown by the red points, which have distinct properties. So if this is from another merger with the Milky Way when did it happen? Well it’s by looking for the youngest cluster in each group that you can put an estimate on when the merger occurred, since any clusters that formed after that would’ve then been part of the milky way in the black group. But Massari et al. only studied 39 globular clusters, so there’s probably more that they’ve missed from these populations. So they modelled what the likely relation between age and metallicity should look like if you could observe them all, and find a 1.8 billion year difference in the youngest age of the clusters compared to the Gaia-Sausage Enceladus. Massari et al. have interpreted that as evidence for another merger happening in the Milky Way’s history, 1.8 billion years before the merger that created the Gaia-Sausage Enceladus, or 12.3 billion years ago, when the Universe was just 2 billion years old. They’ve dubbed the galaxy that merged with the Milky Way back then the Low-energy-Kraken-Heracles system, or LKH for short. And one of the reasons this is so interesting of a finding is that simulations trying to recreate the Milky Way’s current shape and properties often predict a merger happening at this time for the Milky Way.... Video filmed on a Sony ⍺7 IV Video edited by Martino Gasparrini: martino.freelance@gmail.com Video produced by Marina Hui & Dr Becky Smethurst --- 📚 My book, "A Brief History of Black Holes", out NOW in hardback, paperback, e-book and audiobook (which I narrated myself!): http://lnk.to/DrBecky --- 👕 My merch, including JWST designs, are available here (with worldwide shipping!): https://dr-becky.teemill.com/ --- 🎧 Royal Astronomical Society Podcast that I co-host: podfollow.com/supermassive --- 🔔 Don't forget to subscribe and click the little bell icon to be notified when I post a new video! --- 👩🏽‍💻 I'm Dr. Becky Smethurst, an astrophysicist at the University of Oxford. I love making videos about science with an unnatural level of enthusiasm. I like to focus on how we know things, not just what we know. And especially, the things we still don't know. If you've ever wondered about something in space and couldn't find an answer online - you can ask me! My day job is to do research into how supermassive black holes can affect the galaxies that they live in. In particular, I look at whether the energy output from the disk of material orbiting around a growing supermassive black hole can stop a galaxy from forming stars. http://drbecky.uk.com