From Dr. Becky.
AD – Click this link https://boot.dev/?promo=DRBECKY and use my code DRBECKY to get 25% off your first payment for boot.dev. | Here’s two things that we know to be true about black holes: 1) when a massive star dies and goes supernova, the core of the star collapses under gravity to form a black hole that’s heavier than 3 times heavier than the Sun. 2) There’s a supermassive black hole at the centre of every galaxy, every island of stars in our Universe. And they’re anywhere from a million to 10s of billion times heavier than the Sun. But those two facts, that we have lots of evidence to support, means that we have a gap, both a knowledge gap and a mass gap, where we don’t find any black holes between 100 to 100,000 times heavier than the Sun. The only way we know to make a black hole is through a supernova, making the smaller star mass black holes, so the supermassive ones if they start out that small need to grow slowly through that mass gap until they reach supermassive status. So why don’t we find any of these intermediate mass black holes…?
Chang et al. (2025) – https://assets.science.nasa.gov/content/dam/science/missions/hubble/releases/2025/07/STScI-01K0T9HB0Q878FTVP923EYC7MW.pdf
Farrell et al. (2009) – https://arxiv.org/pdf/1001.0567
Fiorito & Titarchuk (2004) – https://arxiv.org/pdf/astro-ph/0409416
Freire et al. (2017) – https://arxiv.org/pdf/1706.04908
Kiziltan et al. (2017) – https://arxiv.org/pdf/1702.02149
Ma et al. (2007) – https://arxiv.org/pdf/astro-ph/0702012
Titarchuk & Seifina (2016) – https://arxiv.org/pdf/1609.00780
00:00 Introduction
03:57 How we find black holes
08:39 Why IMBHs are particularly hard to find
12:06 The possible candidate IMBHs that we know of
16:16 Bloopers
Video filmed on a Sony ⍺7 IV
Video edited by Martino Gasparrini: https://www.fiverr.com/mgs_editing
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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.
