Oh, getting ready to take part in some chats. It's been a little while, hope my typing skills are fast enough.
About My Activity:
Hello all, I’m a winner of I’m a Scientist June 2019. I work with the dust around supermassive black holes and try and use them to find out more about the universe.
I was not an exhibitor at the Big Bang Fair but I have recently taken part in Fame Lab and used popping balloons to explain supernovae.
About Me: A UK/US dual national at the University of Southampton. My life is dust.
My name is Bella Boulderstone (she/her), I’m a PhD student at the University of Southampton. I’m a dual UK/US national. I’m 27 years old. I like badminton, Eurovision, feminism, Star Trek, David Attenborough nature documentaries & the NFL team the 49ers. I have a 1174 day streak (as of 11/03/2020) on Duolingo (I’m trying to learn Spanish). I’m currently training for my first 10k, which I expect will be exceptionally slow.
My Work: The dust around supermassive black holes
So, at the centre of most galaxies lies a supermassive black hole. This is a lot of information to take in and usually prompts a few questions:
- What is a black hole?
- What happens when I fall in one?
- Just how big is supermassive?
And those are pretty good questions. Here are some answers:
- A black hole is essentially a hole in the fabric of spacetime. Which also, is a lot of information. If you imagine that all of space is some big stretchy fabric, then all the planets and the stars and the galaxies sit in what are called ‘wells’, like a dimple. The size of the space dimple (or well) is dependent on how much stuff there is in it – how much mass it has. The way we (as humans) see the Earth’s space dimple is as gravity. Everything that is made up of stuff, has gravity associated with it.
Great. So everything travels on this stretchy dimply space fabric stuff. Even light itself travels along this stuff. Now imagine, that there’s something on the fabric that is so heavy, that things can’t even escape from it. That there’s a hole in this dimply stretchy spacey fabricy stuff.
That’s a black hole. They’re objects that are formed by huge exploding stars (supernovae) which leave behind a central core where nothing can escape. But things do rotate around black holes, and that’s important
2. What happens if I fall in one?
Ok, so you’re an astronaut and you see a black hole and you go, ‘Hey, it would be great if I were to take a quick trip to a black hole, what could go wrong, right?’ WRONG. So many things could go wrong!
You end up as spaghetti. Or, spaghettification, real scientific term for what happens to you if you decide to take a trip to a black hole. You get spaghettified. Which is exactly what it sounds like. If your fellow astronaut watched you as you fell into the black hole, that’s what they’d see.
3. Just how big is supermassive?
Well, a ‘small’ black hole can be 5-10 times the mass of the sun and a ‘supermassive’ black hole can be a million times the mass of the sun. So there’s quite the range. It’s worth noting that the sun’s mass (how much stuff the sun is made of) is about 100000000000000000000 kg. Which is so heavy, it doesn’t really bare thinking about.
But this isn’t really the bit that I do. So, at the centre of these galaxies, the black holes hang out and they can grow by stuff falling into them. This is called accreting and produces a lot of energy around the black hole (Not coming out of it, nothing can come out of a black hole). This stuff that’s falling into the black hole forms a flat disc structure (like a CD, if those even still exist anymore) and swirls around the black hole until it eventually falls in. Being ripped apart and spinning fast and all sorts. This flat hot, spinny bit is called the accretion disc.
The famous picture you may have seen recently of the black hole shows the black hole at the centre and the accretion disc:
Ok, so we have the black hole, and the accretion disc, I gotta do one of these things, right? Sorry!
So, outside of that, there’s some dust. It acts as a way for all the stuff in the galaxy to funnel onto the accretion disc so that it can funnel into the black hole. It’s in a sort of donut shape, but if the donut was made of a lot of little dust clumps.
The inner edge of this donut is set by the dust sublimating – turning straight from a solid into a gas like dry ice. This happens at a specific temperature which relates to the infrared bit of the electromagnetic spectrum.
This dust absorbs the light coming from closer in and then re-emits it, just with a bit less energy. This means that all the variations in the light closer in will be seen in the light further out. Basically, the dust is creating a space echo.
And that’s cool, because then we can find out sizes. So speed = distance / time (the only equation I’ll use I promise) and we know that light travels at the speed of light (which is great, very handy) and we can find the time the light takes to echo, so we can find the distance the light travels to make that echo!
Why do we care about space echos?
So, space has this really awkward problem. How can you tell if something is small, dim and close or bright, big and far away? We work a lot on finding things that we can use as ‘standard rulers’ or ‘standard candles’. This is the ‘scale’ of the universe.
Like in this map of Southampton here, it has a scale so you know how far away things are from each other. That’s what we’re trying to find, the ‘scale of the universe’.