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all right professor what do we got today from the messier catalogue messier 88. well that's a pretty one it is gorgeous spiral galaxy have we missed that one until now that's great yeah it's good to save a few of the good ones up in that really this is one of the ones that messier himself found in fact he had one really good night in march 1781 i think it was where he found nine objects in one night of which this is one of course it didn't look like that to him no he would have seen it as a bit of a fuzzy blur if you look a bit more closely at it there's something a bit peculiar going on right because it's not actually symmetric you can see it's diffuse and fluffy on this side but actually quite concentrated on
that side so it doesn't have a perfect symmetry to it and there is a good reason for this and actually it's the same reason why messier got lucky and found all those objects in one night which is that this is in the virgo cluster so the whole load of galaxies in the same bit of the sky and this is a spiral galaxy which is in the process of falling into the virgo cluster and in fact the reason why it's sort of so squashed on this side is because it's sort of heading in that direction so that's the side that's feeling the impact of the wind that's kind of crashing into it so here's a paper where they were looking at ngc 4501 which is another name for messier 88 and looking for this sort of the effect
of the material getting stripped out and sure enough when you look at the atomic gas here so this is the hydrogen gas in this thing you can see there's this high density region on the that leading edge and then sort of lower density material on that side so then you can move on and look at the molecular gas as well so there's yet another paper and ngc 4501 is one of them and again when you look at the molecular gas not quite so clear in this picture it's quite truncated on this side where it's all getting squashed up and it's more kind of diffuse on that side boring you with all the data here but the last thing you can look at is what fraction of the gas is molecular versus atomic right how much of it is
atomic hydrogen how much of it is molecular hydrogen so this is the ratio of the two and what you again find is on this leading edge there is more molecular hydrogen and less atomic hydrogen and that's basically again this effect of compression that as you squash the material together obviously it all gets kind of closer together so you end up with more gas there but as you squeeze atomic gas together you start actually turning it into molecules start producing molecular hydrogen as well so the reason why astronomers are very interested in molecular hydrogen is that's usually the density of material that turns into stars if you just let molecular gas form naturally then you
end up making lots of stars if you really force the molecular gas to form by compressing it very hard you form those stars in this case it's sort of the star formation rate measured in that area is down by about a factor of two so it's clear that the it's getting sort of squashed a bit which is suppressing the star formation a bit but it's not so violent a phenomenon that it stops stars forming altogether so most of the hydrogen out there is atomic it's not h2 it's just h yep mostly atomic hydrogen just because most of the gas in the universe is so diffused that hydrogen atoms just don't bump into each other very often so you end up not producing molecular hydrogen because here on earth
you would almost never find atomic hydrogen would you yeah but and it really is because most of space is very close to a vacuum and so the really the densities that we're typically looking at there are very much lower than what you'd find in the lab so this leading edge where all this compression is happening when you first started talking about it i was imagining it was going to be a really bright energetic place but because there's not much star formation there is this actually a darker part of the galaxy you've produced this molecular hydrogen so you are actually making stars there so if you look in ionized hydrogen for example hydrogen alpha which is the gas that you see where there are very bright
young stars that are ionizing the gas there is some there so there is star formation going on that leading edge but not maybe quite as much as you would expect from the amount of molecular material there just because this process of squashing that gas together has sort of suppressed the star formation i mean you'd be hard-pressed to say it's a you know it looks a bit brighter right and i think that's basically reflecting this star formation that's going on there but there's two things going on there right because partly it's brighter just because it's got squashed and so the stars are closer together so you end up with a kind of a higher brightness area but also there is a degree of style formation going on there
as well what would it be like to live near that leading edge on a planet around a star there compared to other neighborhoods of the galaxy i doubt you'd notice to be honest it is one of those weird things about galaxies that are mostly empty space you know in terms of if you were actually so close to it that you were living on one of the stars within that galaxy you know the next nearest star would still be light years away so you probably wouldn't notice very much different there to compare to any other part of the galaxy does m88 have a cool name it looks good enough that it feels like it should have a cool name it should do isn't it not that i'm aware of no you guys got to catch up with naming these
there's just too many things out there that's trouble too many cool things to look at you can't give them all names how old are they and perhaps something we call the destruction time scale which is quite a doomsday thing to talk about so once they have form there's a couple of things that can happen you get star interactions in a global cluster so you have like flybys of stars
