From Dr. Becky.
AD – To try everything Brilliant has to offer for free for a full 30 days, visit https://brilliant.org/DrBecky and you’ll also get 20% off an annual premium subscription. | Just like in biology, astrophysics has its own “what came first, the chicken or the egg?” question. In this case it’s “what came first, the galaxy or the supermassive black hole?” Because as we look at the Universe around us today we find that at the centre of every galaxy is a supermassive black hole, and what’s more is that how heavy a black hole is, is tied to how heavy its galaxy is. The two are correlated. So we interpret that as galaxies and their black holes growing together, evolving together. If you grow one, you grow the other, along that correlation line. But if we think about what would happen if we rewound time, back to the early days of the universe when stars were just beginning to form, did the black hole form first, and then the galaxy of stars form around it? Or did a galaxy of stars form first, one of them die and go supernova and become the central black hole? To work that out we have to look back in time, because light takes time to travel to us, as we look at more distant objects the light has taken longer to get to us and we’re seeing them as they were billions of years ago. So the further back we look, the further we rewind time and get closer to answering that question of chicken or the egg; galaxy or black hole. Thankfully, we now have the James Webb Space Telescope, that has been designed to detect the faint light from very distant objects, and since its launch in 2021 there have been high hopes JWST would help crack this age old question…
Geris et al. (2025) – https://arxiv.org/pdf/2506.22147
van Dokkum et al. (2025) – https://iopscience.iop.org/article/10.3847/2041-8213/addcfe
Agarwal et al. (2016) – https://arxiv.org/pdf/1510.01733
Bowler et al. (2017) – https://arxiv.org/pdf/1609.00727
Bogdan et al. (2024) – https://arxiv.org/pdf/2305.15458
Harikane et al. (2023) – https://arxiv.org/pdf/2303.11946
Maiolino et al. (2024) – https://arxiv.org/pdf/2308.01230
00:00 Introduction
03:45 Paper 1: The lowest mass supermassive black holes spotted with JWST
09:03 Paper 2: A direct collapse black hole with JWST?
13:50 Which came first: the galaxy or the supermassive black hole?
14:14 Bloopers
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👩🏽💻 I’m Dr. Becky Smethurst, an astrophysicist at the University of Oxford (Christ Church). 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.
