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so today i want to talk about messier which is another spiral galaxy and as you know they're my favorite yeah it's about 22 to 25 million light years away what is cool about it is that it's what's called a seafood galaxy and it's actually the nearest seafood galaxy to us so seabird galaxy is a class of galaxies with actively growing supermassive black holes so we think in the center of every galaxy basically you have a black hole that sort of sits in the gravitational driving seat right and when you look at the light from those galaxies you'll see that in the center you get like x-ray radiation and radio radiation as well that's coming from basically the super massive black hole
accreting material but what ends up happening is that as that material like spirals around the black hole waiting basically to be accreted like the pressure in that scenario is like massive right and basically the gas heats up due to friction and it like starts to glow in x-rays and then that x-ray gas can then hit into hydrogen gas and then it basically excites electrons in the energy levels so you have like a proton in the center of the nucleus and you have an electron going around it basically if it gets hit by like x-ray radiation it'll jump up to the next energy level and then when it's like i don't actually want to be up here because this is not the place i'm supposed to live it drops back down and then it gives off light and quantum
mechanics says that those energy levels are always separated by the same amount of energy so it always gives off the same amount of energy so the light is always the same color or wavelength and so when we look at the spectra of these galaxies we see these very sharp peaks in the emission now we see also that in emission nebula in our own milky way galaxy so this is like star forming regions you know like the orion nebulae you get the light from star formation also triggering the same process in gases around the nebula and you get emission lines from it they look a lot different though in this in these seafood galaxies so this is a spectrum of the orion nebula and you can see that all the different wavelengths occasionally we get these really sharp
peaks of emission and that's from say this one here is from hydrogen okay and a bit of nitrogen mixed in as well in a couple of peaks that sort of blur together but basically that's always at that same wavelength and we see that very clearly now this spectra over here is of one of these seafoot galaxies so it's a different galaxy i couldn't find this specific one for this one straight away but this is for a seafoot galaxy and you'll see it also has the same kind of emission but you can see actually instead of being very sharp peaks these ones are kind of broadened okay they're not a sharp this is sort of like 400 angstroms wide here where before they were only sort of like 10 and 20 angstroms wide if that in the
1940s when seifert first looked at this he realized that they were different to sort of a mission they believe we saw in our own galaxies and that they were this sort of like smeared and broadened out emission and that all comes from the fact that your gas in your galaxy is actually sort of spiraling around the black hole so some of it is coming towards you and some of it is coming away from you and so some of it's redshifted and some of it's blue shifted and so you get this sort of smearing out to different wavelengths as it spirals around the black hole which is like pretty cool right so the reason i wanted to talk about m106 though is because it contains what we call a mega mazer
which is like the most astrophysical sounding word i've probably ever come across right it's a mega mazer quasar a quasar is the name we give to sort of any growing supermassive black hole ones that are extremely bright in like x-rays or radio so this is a mega mazer quasar which i kind of always want to just push together so that it's just a mazar in your window one word so maser is actually an acronym for something and if you think it sounds a lot like laser you would be right so a laser is light amplification by stimulated emission of radiation and a maser is microwave amplification of by stimulated emission of radiation so basically it's the same thing as a laser but in the microwaves rather than
like optical and infrared that we use lasers for every day so a laser is basically light of all the same wavelength that is very highly like collimated and directional so it's like all going in exactly the same direction and it's extremely bright the same thing is true of a mazer it's very collimated all the same wavelengths and very directional as well emission of light a very specific wavelength now that might sound quite similar to what i was describing before in terms of like the emission nebula that we see and this in the emission lines in the seafoot galaxy spectra that we see as well but it's actually very different so if you have like imagined sort of like a collection of atoms and particles
like hydrogen gas for example okay and you've got you know protons with your electrons around them and just hanging out in this hydrogen gas right if you put energy onto that gas there's like one of two things that can happen so the first one is what we call like random spontaneous emission which is what i described before basically energy comes in randomly causes the electron to jump up to its next energy level and then it will just spontaneously decide to drop back down again so it's what we see when we look at the spectra of like nebula and galaxies and stars everything that tends to be just this spontaneous emission of light from the spontaneous drop down of these electrons the second
thing that can happen though is that the light comes in is so energetic that more than half of the atoms in your hydrogen gas have the electrons jump up to the next energy level right so you've got like a really sort of loaded gas right and what then that means is that more energy is still coming in the form of like x-ray photons for example from you know the gas around the supermassive black hole and then what can happen is that as that photon comes past the atom of the galaxy with the electron already excited it actually stimulates the electron to drop back down and in doing so the electron gives off light with the same wavelength as the light that came in and also in the same direction as well so you end up with
this actual like cascade of light that ends up being very directional so all the same direction on all of the same wavelength as well so it's very collimated like a laser but with the radiation that's coming off supermassive black holes they're so energetic that these things are a hundred times brighter than anything we see in our own milky way hence megamazer so m106 is megamazer is a h2o vapor megamaser which means it's basically electrons that are excited around water molecules and all the energy comes from the x-ray radiation from the supermassive black hole a lot of people have studied m106 with radio telescopes and have tried to observe the spectrum of this emission from this h2o megamazer because then two things you can do with
your mega mazar like a biggest arm again so there's two things you can do with your megamazer observations so this one was miyoshi in 1995 who basically first of all measured the mass of the black hole using one of these mazes so this plot here is the spectrum that they get of this mazer in m106 what you can see is that yeah it's not one single peak it's lots of different peaks that are first of all well above like the generic sort of level of light you're getting from the galaxy but there are all different wavelengths because they've been shifted depending on where they're seen in the galaxy so there's sort of like different clumps of the gas around the black hole it's like not like a smooth thing there are clumps that are emitting
um that have enough energy to produce this mega mazer and so you get the light from these different clumps and all those are moving at different speeds around the center of the galaxy and so they're shifted depending on what speed they're moving around the galaxy so we see all those peaks so this paper that came out in 1999 they worked out that with this same data you could actually work out how distant the galaxy was purely from the geometry of where those clumps were around the center of the galaxy so they have a cool little sort of infographic that you can see here's the same plot that they had in that previous paper which is just the spectra of light and basically sort of
stuff on this side you can attribute to clumps of h2o vapor with your mega mazer on this side of the galaxy and stuff on this side is these clumps over here and the bright stuff in the middle is the stuff like sort of right in front of the the central supermassive black hole so i think those contours they're showing there are like the x-ray or radio data from the supermassive black hole and this is sort of the warped disc model that they've come up with to explain these clumps of these mazes so if we think about what the geometry of this system actually looks like right it would look probably a little bit like this okay so this is the black hole at the center of the galaxy right and you have one of these
clumps of like mazar emission over here that is a distance r from the center of the galaxy and possibly it's going round the black hole like that if we're sort of observing down here this is my nice eye on planet earth and we're observing that black hole on that mazer then first of all it's going to be a distance of d away from us and then also this light here is going to come out to us a different angle than d and so that's going to be sort of separated on the sky by that angle as well right we're also then going to measure the rotational sort of velocity it's coming towards us at so this is sort of the velocity that you measure but in reality it's actually sort of going round at like a rotation
velocity like that which we don't measure that's also obviously then going to be at some angle in the galaxy as well so you've got to think about like what we know and what we don't know so we know the mass of the supermassive black hole from the previous paper we are trying to find this distance right we know this and we know that using all of that information and the fact that you've got a load of those different clumps that you can model you can then use that to cancel out the things you don't know and actually find what the distance to the galaxy is which is how we know that it's like 22 to 25 light years away which might not sound very precise but that all depends on you know what model of the universe you
assume as well to do that um but it's actually one of the most accurate measurements of a galaxy we have like it's we know that it's sort of right within like three percent which i mean we have measurements that are more accurate than that in our like own local group of galaxies so the milky way andromeda and like the magellanic clouds but outside of that's the most accurate distance measure we have and so these mega mazes are really useful in giving us a sort of step on what we call the distance ladder in cosmology like determining even greater distances you know how do we calibrate redshift with distance in the universe most useful for the observations that we do is to extend
that project that system of longitude and latitude onto the celestial sphere expands out plot every single integer negative and positive
