M89 - How round is this galaxy? - Deep Sky Videos

my kids need to credit in this I've stolen stolen so many things from their toy box three different videos today we're on Messier 89 which is a galaxy in the Virgo cluster it was discovered by Messier on one very productive night the most productive night of his hunting for Messier objects he discovered eight galaxies in the Virgo cluster and a globular cluster all on the single night what's remarkable or a little different about it is that it's perfectly round or appears to be perfectly round on the sky so it's the type of galaxies that we call an e zero or an elliptical class zero object so this goes back to a very famous classification that was first devised by Edwin Hubble we call it the Hubble tuning fork diagram and this is a completely empirical way of classifying galaxies so this is just Hubble taking all the galaxies he can see and putting them in some sort of system according to what he thinks they look like and so we've got the two classes we've got the elliptical galaxies and then we've got the beautiful spiral galaxies that we always think of and they go out in two branches because one branch has an extra feature that's a bar but otherwise they get sort of more loosely bound spiral arms and smaller bulges in the center and then as we go from the along the elliptical branch we've got the really flattened elongated galaxies the e7s all the way down to the perfect apparent circles that are the e0 now the reason I'm using words like apparent and appears is because we don't know the galaxies three-dimensional shape from an image this is one of the intense frustrations of being an observational astronomer that you see a universe that is three dimensional projected into two dimensions and whether it's talking about the shape of an individual object or the structure of the entire universe along the line of sight we can use tricks and physics to try to infer some of that extra information that third dimension but we never know for sure we can't turn the universe around we can't wait hundreds of millions of years for our orientation to change I thought red shift and blue shift to solved everything for you and you knew how far away everything was could then plot it three-dimensionally using that well that's the next video back to our galaxy so I've set up a little experiment here and if this goes correctly it's a little unfair because these are galaxies made out of play-doh and light shining from them and you're getting extra information that way if you look with the camera or if you look with just one eye so that you don't have stereoscopic vision hopefully what you'll see through your viewfinder is that you've got three galaxies that all look very similar they all look very round okay and so this is this is what we might see in an image and this is what we're faced with with m89 the question is is it really a round spherical object seen from all three dimensions or in the case of these galaxies is it something different so here's our round spherical galaxy and it looks the same no matter which angle that you look at it from but these ones look quite different this one is roughly the hot dog yeah we call it a prolate galaxy it's meant to be kind of rugby ball shaped and that's the galaxy that maybe has some rotation the Stars or rotation preferentially symmetrically about the long axis so that's the cigar shape but seen end on it still looks round and then the other possibility is a galaxy like this this is an oblate galaxy and it's the same idea this time the stars might have a preferential wrote with rotation around this direction that's a baby Boujis yeah so it's flat but again seen from the right perspective you wouldn't be able to distinguish it there's another class which is a triaxial galaxy in which there's no preferential axis of rotation there's you know there's there's three axes to the shape but but no no symmetry in the rotation and so that's basically where we are which which get which galaxy is m89 I can't tell you for sure you might make the argument that you're more likely to it's more likely to be this one because you can see that shape from every other angle but then there's physical explanations that say a low redshift that we might be more prone to seeing oblate galaxies we might have to just wait a few hundred million years to find out which one it is you can make sort of statistical arguments on classes of galaxies because you can say right well it will be they'll be concentrated surface brightness for prolate galaxies if you're giving them this way whereas these ones will be more concentrated because you're seeing more stars along that axis if you look at a whole population you might be able to infer if you've got more of one than the other the other interesting thing about this is that although in in the image that you might see it looks like just a really very smooth very very round very symmetric boring looking galaxy if you looked at the right way as so often happens you see some interesting things so this was one of the first galaxies to be determined to be have shells around it shells of stars the way this was found was using very very deep imaging on photographic plates with telescope in Australia and those very deep images revealed some very faint stellar structure around the outside and so this is an image from a paper published in 1979 in the journal Nature by an astronomer and famed Astro photographer David Malin and you can see where as the original image was just some small little round thing it's much smaller than the scale of this image this really deep image shows structure extending hundreds of thousands of light years away from the central region you can see little edges and shells you can see this structure around here and you can see a linear structure which they called a jet but which is actually likely the distorted remnants of some little dwarf galaxies that's being pulled apart by the gravitational force now we know that if we look at many elliptical galaxies like this if you look faint enough if you look carefully love you see the remnants of shredded galaxies which is how we think these things are built up in the first place by mergers by cannibalism of smaller galaxies and this is sort of seeing it in action oh wow you didn't tell me it was this cold look at this like Indiana Jones right now just so you know I don't actually need this light I just think it looks cool

Channel: DeepSkyVideos

Views: 92,721

Rating: 4.9558535 out of 5

Keywords: astronomy, messier 89, galaxy, elliptical, hubble

Id: ySqqRoKpuTI

Length: 7min 6sec (426 seconds)

Published: Fri Mar 31 2017