Go to https://brilliant.org/drbecky to get a 30day free trial and the first 200 people will get 20% off their annual subscription! Everything we know about the Universe suggests that supermassive black holes in the centres of galaxies should merge together, BUT the maths tells us that supermassive black holes will never merge together; instead forever orbiting each other at a distance of around 1 parsec (3ish light years). How are we going to crack this problem? That is, if it even is a problem at all...

My previous video on why we think there's a SMBH in the centre of every galaxy:    • How do we know there's a black hole i...  
My previous video on why LIGO can't detect gravitational waves from supermassive black holes merging:    • Why can't LIGO detect mergers of supe...  
My previous video on the gravitational waves detected by pulsar timing arrays:    • Astrophysicist explains big GRAVITATI...  

Hopkins et al. (2007; correlations between SMBHs and galaxies in simulations) https://arxiv.org/pdf/0707.4005.pdf
Kormendy & Ho (2013; correlations between SMBHs and galaxies in observations, REVIEW) https://arxiv.org/pdf/1304.7762.pdf
Chandrasekhar (1943; dynamical friction PART 1) https://articles.adsabs.harvard.edu/p...
Chandrasekhar (1943; dynamical friction PART 2) https://articles.adsabs.harvard.edu/p...
Chandrasekhar (1943; dynamical friction PART 3) https://articles.adsabs.harvard.edu/p...
Begelman, Blandford & Rees (1980; final parsec problem outlined, BEHIND PAYWALL students should be able to access) https://www.nature.com/articles/287307a0
Iwasawa, Funato & Makino (2006; a third black hole solves the FPP) https://arxiv.org/pdf/astroph/051139...
Berczik et al. (2006; more realistic galaxy model solves the FPP) https://arxiv.org/pdf/astroph/060169...
Milosavljević & Merritt (2003; recycling of stars solves the FPP) https://arxiv.org/pdf/astroph/021245...
Mezcua et al. (2014; dual AGN decomposition in mergers) https://arxiv.org/pdf/1401.5920.pdf
Hardcastle & Croston (2020; review of radio galaxies) https://arxiv.org/pdf/2003.06137.pdf
Thorne & Braginsky (1976; gravitational wave detector proposal) https://articles.adsabs.harvard.edu/p...
NanoGrav PTA research papers https://nanograv.org/news/15yrRelease
EPTA & InPTA research papers https://www.epta.eu.org/eptadr2.html
Parkes PTA research papers https://www.atnf.csiro.au/research/pu...
Chinese PTA research papers https://iopscience.iop.org/article/10...
AmaroSeoane et al. (2012; eLISA proposal) https://arxiv.org/pdf/1201.3621.pdf

00:00 Introduction
00:56 Why do we think supermassive black holes merge together?
02:23 What physical process brings supermassive black holes close to each other in a galaxy merger?
05:18 What is the final parsec problem? Why SMBH binaries stall at 1pc separation
09:12 What observations can help us work out if this really is a problem? (Dual AGN, radio galaxies & LISA)
13:56 Brilliant
15:17 Bloopers

Video filmed on a Sony ⍺7 IV



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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.


http://drbecky.uk.com
https://rebeccasmethurst.co.uk