What is Causing the Mysterious Dimming of Betelgeuse? with Dr. Andrea Dupree

[Music] you have fallen into event horizon with john michael gautier in today's episode john is joined by dr andrea jupri dr andrea dupree is a senior astrophysicist at the smithsonian astrophysical observatory which forms part of the harvard smithsonian center for astrophysics in cambridge massachusetts dr dupree received a ba in astronomy from wellesley college and a phd in astronomy from harvard university her research focuses on cool stars like the sun and their planets to understand how they are born and how they evolve with particular emphasis on the analysis of spectra she and another member of the kepler team ron gilliland obtained the first image of the surface of a star betelgeuse using the hubble space telescope dr dupree has published several hundred scientific papers and articles and edited several books she is a past president of the american astronomical society and has served on and led many committees of the us national academy of sciences nasa and others to determine the future course of astronomical research in the united states and other countries she held the position of associate director at the harvard smithsonian center for astrophysics the first woman and youngest person in the position and served as head of the solar stellar and planetary sciences division of the cfa dr andrea dupree welcome to the program well thank you i'm delighted to be here now doctor among many things you study the giant star beetlejuice in orion that we all know and love from its red color well not long ago beetlejuice started behaving a little bit oddly and very visibly dimmed and no one really knew what was causing it why it did that but then again beetlejuice is a variable star and has been known to be such for a very long time but this was sort of out of character even for beetlejuice and at the time there were a bunch of hypotheses floating around of what might be happening here including a run up to a supernova are we closer to understanding exactly what caused that first dimming event with uh beetlejuice well we think we have some strong indications from our hubble observations about what went on but i also must underscore that the constellation looked so unusual this january in february i mean this star which we know and love you know the bright red star and the shoulder of the orion constellation just vanished it got really dim and the constellation just looks completely abnormal but i think i think we have an idea of what's happening and this comes from a program that i led on the hubble space telescope now hubble is an amazing instrument because uh it's above the earth's atmosphere so it doesn't uh subject any of the the data the information to blurring and things like that and it also has a very small field of view with its spectroscopes now a spectroscope is an instrument that takes light and from the star and breaks it up into colors and from that light we can tell what the star is made of we can tell what what the star is doing what different layers of the star are doing are they moving in are they moving out what what's happening with the star and the fact that betelgeuse is close that makes it also big and the fact that we're also looking in the ultraviolet part of the spectrum where betelgeuse is even bigger than what we see with our naked eye or in the optical part of the spectrum meant that with hubble we could actually look at the spectrum look at the colors of the light from different parts of the star we could move hubble across the image of the star and find out what's happening in different parts of the star whether the north was moving in or out or whether the south was moving in or out and what we found was very interesting we've been looking at bail juice starting at the beginning of 2019 and we observed it we made a visit in january and another visit in march and everything looked fine and normal and nothing surprising was present but then when we got back to betelgeuse in september because you know that because the earth moves sometimes betelgeuse gets very close to the sun and we're not able to see it from the earth but when september arrived we could point at the hubble telescope back at the star again and what did we find we found that in the southern part of the star this is the southern quarter of the star there was a huge bright hot mass of material that was just moving out and we could tell this by looking at the shapes of the lines we could measure the shapes we could measure the velocity and we could see that there is hot material we could also see that it was very dense it was much denser than the other material on either side or in the north or in the east or the west so in the south for september october and november we saw this enormous cloud of dense hot material moving out now that gave us a clue especially since at the end of december we used an imager at the european southern observatory in chile and we were able to actually take a picture of of betelgeuse in the optical region you know like in the light that that you see normally and with you know with your own eyes and we found that the southern part of the star was faint it was dim it was if there was something in front of the southern part of the star and then it got worse the light of the star as you know betelgeuse got fainter and fainter and fainter reaching a minimum that's three times fainter than it normally is at the beginning of february and as a matter of fact this is historic you know people first started making um written records and observations of betelgeuse back in 1840 sir john herschel in england started measuring it and it has never been as faint as it was in february of 2020 so what happened well our speculation is that what we found with hubble this big cloud moving out move further out in the atmosphere of the star and you know it gets cooler as you move farther away from the surface of the star and we believe that this hot material cooled down and then condensed and formed dust you know like soot or something so it's like a dark cloud in front of the southern part of the star and that's why we believe that betelgeuse appeared faint and even fainter the cloud may have developed and then finally it dissipated so that by the time april came around betelgeuse was back to normal now what would this sort of material being ejected from the start look like is this like very tiny submicron dust like carbon or something or is it bigger material what what's it like well there's different things and when it when we're moving we're close to the surface of the star we're above the photosphere of the star the visible surface it's a hot gas so it's a it's a very very hot gas and then as it moves out it it really goes into sort of grains i mean uh you know material like like dust like soot and what it's made of is something that we're trying to calculate right now we have many images of it taken through the late winter and early spring and some of my colleagues are trying to model this using all the information we have about how how how it varied uh what the color of it might be and trying various models of various compositions to see if they can reproduce the observations that we see beetlejuice is a noteworthy star because it's close and it's huge therefore we can image its disc did we get any direct images of the disc of beetlejuice while it was dimmed like this in the southern part of the star yes yes we did we did using an interferometric instrument on the telescopes in chile that are run by the european southern observatory it's an instrument called sphere like a like a like a ball sphere and we could actually image of the star and this was put out on actually on valentine's day and you see the bright top of the star it looks and and the but the bottom is just very very dim and we could compare it to something we had taken earlier in the year in january when the star looked perfectly normal it looked round and maybe there was a bright spot in the north and um uh it looked perfectly as i said normal but in december and subsequently this this cloud developed over the southern part of the star now the star invisible light obviously very much dim in other areas of the spectrum what did it do i mean was there sort of any infrared or ultraviolet or anything else that um well yeah that was the clue that we got from hubble which is an ultraviolet spectrum in in the fall in september through november we had ultraviolet spectre from the hubble space telescope and that's what gave us the clue to this hot material that was moving out we could see that it was moving out we could see that it was very hot and it was very dense we couldn't measure this from the ground because the the spectrum that one measures on the ground generally is more of the surface of the star it's not of the layers above the surface of the star so we think that something happened during the summer uh and you know you mentioned betelgeuse's pulsating well you know there's something very interesting not only was betelgeuse moving out the atmosphere the surface was moving out from january through november or december of 2019 but at that time we believe there was a huge convective cell we have imaged betelgeuse uh previously years ago and we know that there are these very big convective cells i mean they take up maybe a quarter of the star and they appear and they disappear it's hot material on the surface that's boiling around and moving around like a chocolate sauce connecting and boiling around in your on your um on your stove and we could see that um by going to the ultraviolet region of the spectrum with the hubble space telescope we could probe these hot layers above the surface where we could see the material moving out now this convection that goes on at beetlejuice is also it's the reason it's not going to survive very much longer um in geologic terms of course time scales but there's always a question yeah beetlejuice is going to go supernova eventually 100 000 years something like that or maybe tomorrow could this be an indicator that beetlejuice is about to explode i know you're not the first person who's thought about that as a matter of fact if you went to social media in february i love that somebody wrote my calculations show that the star is going to explode tonight and then he wrote hashtag hide now i'm not sure where you hide exactly under the under the table under your desk you know the very interesting thing is we don't know how a supernova behaves right before it it uh explodes we don't know whether suddenly it gets fainter as the the surface layers are collapsing in on the core or whether it just suddenly gets brighter the reason is that that people don't have the resources to follow every star in the sky every night and then reconstruct and look back to see what happened with the supernova when a supernova occurs now people do know maybe oh six months before a year before two years before how a star behaves but if you really want to go hide under your desk because something's happening tonight we don't know what to look for if the star did explode [Laughter] we would see that pretty prominently right oh yes some people even say you'll see it in the daytime and it will cast shadows we shall see i don't know if we will see in our time our lifetime but uh it certainly would put a damper on nighttime astronomy because you'll have something that's brighter than the full moon very obvious in the sky and you realize of course that because of the fact that light takes time to travel from that star to us that if it has exploded it's already exploded and the the message is on its way okay because uh betelgeuse is about 750 years light years away and so if you subtract you know 750 from 2020 i think you get something back around 1300 a.d so maybe it already exploded who knows sort of interesting that about the time that someone was seeing the supernova that would eventually form m1 crab nebula about that time beetlejuice might have been exploding something poetic about that but i think it would be really sad because we number one we'd lose beetlejuice and orion wouldn't look right anymore i know i know did you go out and look at it because oh yeah i was i was well i've been an amateur astronomer for over 30 years and i i have never seen anything like that i mean i've seen variable stars but this was unbelievable especially i know i know the whole constellation just looked wrong i mean it wasn't right at all right and it was i mean i'm looking at it and i mean stars that normally should be far dimmer than beetlejuice became the prominent stars of the constellation briefly as beetlejuice dipped now we can we're just now getting to where we can study beetlejuice again and it's coming out of the sunlight and at least from space anyway and it looks like it's dimming again any thoughts it well it is first of all we did see betelgeuse when it was close to the sun and let me tell you how we did that it turns out that the earth of course where our position was looking betelgeuse it was too close to the sun it wasn't behind the sun or near the sun's glass you couldn't see it however we have a satellite that's in the earth's orbit but it is behind the earth in its orbit by about two and a half months so what this means is that when we could not see it from the earth in june the satellite didn't think it was june at all and thought it was mid-march and had no problem so we were delighted to find that the satellite folks this is a satellite um uh called stereo which is trailing the earth right now in its orbit and we used a camera on boards this satellite stereo in order to take several images of the field and we did this in june july and august and we could see that it was getting fainter and it's it's too soon for it to be getting fainter so uh we're not quite sure what's happening whether we're getting another another episode of dust or whether it's just teasing us and it's going to get brighter again we don't know could it be like an aftershock from something related to the original event well you you bring up an interesting point and we're thinking about this now because you know when we observe the sun which of course is a smaller star and and phenomena are are similar in some ways but also different in other ways we find from the sun that there are these phenomena called coronal mass ejections where after the magnetic field it reconfigures material is suddenly ejected from the sun this is a very fast process it happens over you know minutes to hours but then it leaves behind sort of an empty space a place where the temperature may be lower and the density may be lower because all this material has suddenly been ejected from the sun and and that leads us to think what happened with betelgeuse because in betelgeuse this area was much much larger than the equivalent of a coronal mass ejection on the sun i mean remember that betelgeuse has a size it's about a thousand times bigger than the sun and this occupied about a quarter of the of the size of the diameter of of the area of of betelgeuse so this is really really really big we're talking a thousand times the size of the sun and all of a sudden the material vanished and we we don't know what happened we're working on this this requires more than hand waving i think and and so we're trying to think what would happen in other words perhaps there really is a very low density region or a region that's much cooler and and you know at the left left behind because all this material vanished um but it's it's it's an interesting and exciting problem to think about now has anything like this ever been seen with any of the other similar stars to beetlejuice these red just super giant stars not with red supergiants however there's a a flavor of star called uh our corona borealis stars now these stars are also super giants but they're warmer they are they're they're much warmer they're warmer than the sun have a higher temperature in the sun and and they are known to eject a lot of material that turns into carbon carbon dust very very quickly and it causes these stars to lose oh three and four and five magnitudes i mean we're talking factors of a hundred not factors of three and this can happen within days so we see other stars not the red supergiants but these are more like yellow supergiants that do eject a lot of material that substantially changes their brightness and vary so we know the phenomenon exists on a much larger scale than what we've seen with with betelgeuse now another thing that's interesting is where this material came from the star because it looks to us from hubble as if it came from the southeast part of the star and from studies with hubble and with alma which is the radio telescopes in uh in chile we know the rotation we know the axis of rotation of betelgeuse we know how it's the star itself is rotating and and we know that the axis and the pole emerges in the southwest of the star not the southeast of the star and and we suspected and theories frequently suggest that maybe materials should only come from the polar from the rotation axis and we you know we see jets from very young stars and their the jet material is ejected along the axis of rotation of the star but but what have we observed in betelgeuse is different in other words it seems to be coming from the southeast from a different side of the star suggesting that stars can lose substantial amounts of material from anywhere it's it's not so simple so this is introduce sort of another wrinkle into how we understand stars their evolution the mass loss and the structure and the the character of the winds that they're that they're um enduring when i one has to also note the creation of carbon which is very important to life of course well stars make everything you know i mean it's not only carbon but iron and calcium and sodium i mean everything that we know and love to you know to make life and us we are star stuff um yep any possibilities of i know beetlejuice is not that old but is there any possibilities of exoplanets around it or would they have just been gobbled up well uh if they were within uh the orbit of jupiter you realize betelgeuse if you put it at the center of the solar system the surface would extend out to jupiter okay if there were any planets within they've long gone long gone as a matter of fact that brings up another puzzle about the star it seems to be rotating more rapidly than we think we have some idea of as stars are formed and and they start out life on the main sequence and then they they evolve and they become red giants and they swell up um we have an idea of how the rotation should change and they might start spinning very rapidly when they're born and then they slow down well betelgeuse is spinning more rapidly than we expect and actually we had suggested some years ago when we found this we said well maybe it swallowed planets we were thinking of something that would add angular momentum to the star and lately there have been some simulations where people are supposing that betelgeuse started as a binary star and maybe the primary this star swallowed up its companion and that's what makes it spin so rapidly or more rapidly than expected and certainly if planets got in the way they are long gone but it's not clear that they would add enough angular momentum to the star to to spin it up to to what we what we see now that that that brings up something interesting is that you know beetlejuice being as enormous as it is covering the entire orbit of jupiter that ejection that causes dimming was enormous it would have taken up a large chunk of our solar system or at least our inner circle that is correct watch out yeah you gotta i mean first just the titanic scale of such an event imagine if you were up close i know i know i know well it's also interesting because one of one of the current issues in astronomy today is exoplanets and what is the environment that an exoplanet lives in because if you're if an exoplanet is in the middle of a very brisk rapid massive stellar wind this is going to blow the atmosphere of the planet away there's be no hope to have an atmosphere such as we have on earth so we're very interested in knowing where stars lose material and how they lose material i mean if for instance all the material is coming out at the poles and the exoplanets are in the equator just as similar to to what we see in our solar system then there might not be a problem but if the star can produce material and and send off a wind in a bursting outflow from anywhere on the star well watch out because it could certainly affect what's happening to the atmosphere of of an exoplanet and we know that some of them have atmospheres i mean that we we've been able to measure and see that there are evaporating atmospheres on some of these uh some of these exoplanets so it's all tied together i mean we might think we're studying how stars evolve but it has many implications throughout astronomy and astrophysics so it has a bearing unlike as you mentioned like evaporating super jupiters and things like that where you see a tail coming off of the planet and eventually what's left you know oh yes no they have they've seen um expanding helium atmospheres um using some very good diagnostics in the near infrared and then what happens is as the exoplanet passes in front of his host star you take spectra very very rapidly and this is back to spectra again which when you take the light and break it up into colors you can find out all sorts of wonderful things about about what's happening at a distance and so then they actually can see the evaporation of the helium atmosphere from the um from the atmosphere of the exoplanet this of course weighs into a debate that's heating up lately about looking for techno signatures around exoplanets gases and things that shouldn't be there like cfcs i know i know there's also room for lots of imagination i must tell you well imagination but at the same time if you if you see cfcs it's i mean there's not much of a way to make that other than a civilization although i we'll see well didn't frank drake's he sent out signals from arecibo years ago and beamed them towards m31 i believe with all sorts of coded signals of of dna and hydrogen and who knows what else and uh they're still listening we haven't we haven't had any answers someone was saying what they're really hearing is howdy duty from our 1950s television sets or something well with the with the arecibo signal i worry that that's someone else's wow signal because we didn't repeat it some alien civilization out there thousands of years in the future will intercept it and go well we need to study that oh it's not there anymore we'll see we'll see so what do you expect for beetlejuice um this coming year i mean it's surprising already so just is do you get a sense that this is sort of but on on monday night this is friday in three more days we're going back to it with hubble so i will find out what what i expect i don't know it may be with with the uh stereo observations we could see that it was getting dimmer and it it's this is before we expected it to get deeper so it it it we had five measures and and it was dimmer and then the last two seemed to be similar as if it had stopped getting dimmer again um but but it's still fainter than average in other words usually it's about oh i don't know half a magnitude 0.5 or something it was down around 0.8 and it may have stopped i we're not sure yet because a lot of the ground-based uh observations are very still very very difficult to make we lost it with stereo stereo you know it moved too close to the sun for stereo to take an image but the ground is beginning to have access to it and hopefully in the next come back come back in a month and we'll have some answers for you now regarding the spectra of beetlejuice and under normal circumstances with the stars big convecting cells do you see changes in composition diamond does it evolve do you see certain elements dredging up as opposed to others um no no really no the time scale is too short for us to for us to see that we we see mainly uh temperature changes density changes and changes in motion in other words we could watch different parts of the star moving to the east and then to the west two months later and things like that watching the sort of swirling motions in the atmosphere but we we do not see any changes in the um in the uh chemical abundance that's that's actually very very hard to measure because you can have changes in physical conditions changes in temperature and changes in density which might might create a change in the emission but it's really not caused by an absolute abundance change it's caused by a change in the physical conditions that change the excitation and ionization of the atoms and ions that are in the atmosphere amazing now doctor i have one other question for you before we finish up when we were uh preparing for this interview we came across how you started your career on a coin flip tell us about that well i went to a liberal arts college where one had to have distribution requirements this is wellesley college an amazingly wonderful powerful women's college in massachusetts and i remember sitting the summer before my freshman year and you had to elect your courses for the year and the first thing a student wants to do is let's get rid of all the requirements right we know we have to take certain things so let's just you know buckle up and do it right now and one of the requirements was a laboratory science and you had to have a year of a laboratory science meaning you had to you know get your hands dirty and wet and build things or explode things or look at the stars and i remember looking at the choices and they were the typical choices there was physics and chemistry and biology and i always went to college with the idea i was going with the idea that i wanted to learn new things things that i knew nothing about because that's why you go to college and i looked at all these laboratory courses and i thought well i had four years of science in high school so i had a little physics a little chemistry a little biology and i thought well there's two things that i really know nothing about geology and astronomy i mean we just didn't have that in high school i went to a public high school in massachusetts and uh we didn't have geology and astronomy and and i didn't know how to decide and i flipped a coin and it came up heads astronomy and then it turned out that i really loved it because it was it was real in other words you could could catch the light from a star or you knew that there were galaxies out there and it was real and and uh it was just a perfect match um so i was a physics major and an astronomy major and it it it's worked out well i still have an adventure or spirit to find out what's going on in our universe i wish you great luck in your continuing uh study of beetlejuice and um i will it's gonna be interesting to see what that star does this year that's right well as i said come back in a month and we'll tell you what's happening it's like it's like mark twain's old adage about the weather in missouri if you don't like it that's right thank you doctor and i hope you'll come back and see us sometime thank you so much okay bye-bye what's that noise oh that's just the new and improved jun but mark ii yeah john pot mark ii like we needed another one i had some funds left over from last quarter so i put them to comical use you had extra funds and didn't tell me i went without beard wax for all of august um about that john hello i am john box anna is great john is not the possum is okay what he doesn't have a beard i know i ran out of money well they are rather expensive now that you say that yes they are we've been footing your beard bill for the past three years i will use the possum as my beard i don't think he's gonna like that wow well that's the end of johnbot number two and on that note join us next week with a chat with the director of the vatican observatory brother guy consolmanu yes they do astronomical research see you then [Music] you

Channel: Event Horizon

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Keywords: betelgeuse, supernova, variable star, betelgeuse supernova, crab nebula, jupiter, betelgeuse dimming, John Michael godlier, Event Horizon John Michael Godier, Event Horizon, when will betelgeuse explode?, Is Betelgeuse Going to Explode?, Why is Betelgeuse Dimming?, ASMR, Andrea Dupree, NASA, astrophysics (topic), Hubble, harvard, smithsonian, What is Causing the Mysterious Dimming of Betelgeuse?, betelgeuse update

Id: riImcGreWSk

Length: 33min 55sec (2035 seconds)

Published: Thu Sep 03 2020