A Sharper Image: Seeing Colliding Galaxies with Adaptive Optics

good evening everyone my name is Andrew frack Noi I'm the emeritus professor of astronomy here at Foothill College in Los Altos and it's a great pleasure for me to welcome everyone here in the Smithwick theater and everyone watching us on the web to this first lecture in the nineteenth annual Silicon Valley astronomy lecture series these free public lectures on astronomical developments and discoveries are jointly sponsored by the Foothill College science and math division as well as by the liquor by the SETI Institute the search for extraterrestrial intelligence the Institute the Astronomical Society of the Pacific and NASA's Ames Research Center one of the premier NASA centers in the country we're delighted tonight to be able to welcome the director of the University of California observatories dr. claire max dr. max is the Baughman professor of astronomy in astrophysics at the University of California at Santa Cruz and as I said the director of the University of California observatories which includes the well known Lick Observatory our first mountaintop Observatory in the country and then the Keck Observatory in Hawaii she is the founder and former director of the Center for adaptive optics a science and technology center supported by the National Science Foundation and in her talk she's going to talk a great deal about the miracle of adaptive optics she's a member of the National Academy of Sciences she has won the Ernest Lawrence award in physics and the Joseph Webber award in astronomy in addition to many honors including I just heard that she's going to be one of the new fellows of the California Academy of Sciences as of next week it's very interesting in this day and age to call a woman a fellow but we won't go into that right now we congratulate her on that honor as well in addition to all her scientific work she is the faculty liaison for education and public outreach at the Lick Observatory appro that includes workshops for local middle and high school science teachers she's had a long interest in making science intelligible for the public at large and as witness to that we're delighted to welcome her to talk today about a sharper image seeing colliding galaxies with adaptive optics please help me to welcome dr. Claire max it's a pleasure to be here delighted that such a large audience is interested in astronomy and I hope to tell you about some of the work that we've been doing liqin Keck Observatory so I'm gonna be talking about really two things one of them is this new technology called adaptive optics and the other is how to study colliding galaxies and what happens to the black holes that are in the core of these two galaxies when the galaxies collide so two different topics but related in a way I'll tell you in a moment and the one slide synopsis of the scientific part is that in most galaxies actually contain giant black holes with masses of a million to ten billion times the mass of our Sun in their core black holes are galactic trash bins they suck in gas which gets very hot as it spirals down into the black hole and we can try and learn something about the black hole by watching the emission of electromagnetic radiation light as the gas falls into the black hole and gets very hot but if each of the two galaxies that are in a collision bring their own black hole to the party then the question is as these galaxies collide they're giant black holes may merge together and form even larger black holes and we'd like to understand how that happens and how that influences the evolution of the galaxies themselves in the future after the merger happens and I need to say that in the history of average galaxies in the universe it's had a major merger a big merger or collision with another galaxy roughly once in the 13 billion years of the universe so this is something that happens to most galaxies and it's not just some little side bizarre phenomenon that astronomers love to study I wanted to and that this all sounds like hyperbole but everything I've said here is a scientific statement that actually seems to be true and I hope to explain a little bit how we know that so I'll first talk about adaptive optics and laser guide stars as Andy said and then I'll talk about how we're using them to study these colliding galaxies and I'll give a summary and then I have some extra secret slides that I'll show at the end if I have time so if you see me dawdling raise your hand and say hurry up okay so here's the intro so here's a telescope and it's trying to observe let's say just a star a regular star the light from the star has to go through turbulence in the Earth's atmosphere and that it turns out is what limits the spatial resolution and the clarity of an image that ground-based telescope can take so we all know that turbulence is why stars twinkle my husband's sometimes teases me that my goal in life has to take the twinkling out of the stars but more important for astronomy turbulence actually spreads out the light from a star and makes it into a blob rather than a ideal point of light which it should be because stars are so far away that we can't see that their extended objects they ought to look to us like points and they don't so this is actually fairly serious the biggest telescopes we have today on earth are eight or ten metres across and they have no better spatial resolution than a little backyard telescope that you may have used in your uncle's backyard or do your aunts amateur astronomer night you are not seeing any more clearly with these giant telescopes than you do with an a good amateur telescope and that's because turbulence messes everything up and we're trying to fix that so I should add what it's what a large telescope can do is gather a lot more light because it's got a lot more area so it's used to observe very faint things so here are three images of a bright star here's a long exposure image if I take a picture for a minute it's about one second of Arc across if those for those of you who think in arc seconds but if you took a very short exposure that's so short that it freezes the turbulence in the atmosphere it's a snapshot in the best sense of the word you wouldn't see a nice round thing at all you'd see what's called speckles these little dots and the next time the turbulence changes you'd see a completely different set of little dots and if you add up enough of these different sets of little dots you get something that's more or less round and it's more or less one second of work across and so what we're trying to do with astronomy is to correct for these distortions and you can think of it in one sense as taking each of these little speckles and piling them on top of each other to get something that's just about at the ideal limit of what a telescope could do even if there were no atmosphere so you can use it aft of optics to dramatically improve image quality for many different contexts I'll show you one and the secret slides at the end of the talk but it's used in industry and medicine and various lots of other interesting places these days so I'm going to go into a little more detail this is very short time exposures of a star greatly magnified and greatly slowed down so this is what the atmosphere does through the image of a star it looks terrible right and if you add this all up it's gonna be some great big spot that big and you'll see also that the middle the brightest point of light kind of wanders around on the within the frame so you have to correct not only all these big expect big cloud of speckles but also you have to try and correct the so that the center of the stellar spot stays fixed and doesn't go off and wander off of these different directions so how do we do that here's here's more cartoons here's your favorite star and you want to look at this galaxy in detail actually I should say this is your favorite galaxy and happens to have a star nearby and you can use the light from the star to measure the turbulence and that works if the star is close to the galaxy because the light from the star goes through the same turbulence as the light from the galaxy so if you can measure it and calculate the shape on a computer to change the shape of it of a special mirror called a deformable mirror that literally puts Wiggles on the surface of a piece of glass and cancels out the Wiggles that the turbulence was trying to oppose on you and then the light from both the star and the galaxy since they go through the same turbulence are corrected and sent to whatever you want to measure them with a camera or a spectrograph and this is in fact done over and over again so you're always almost correcting the turbulence well you flow behind a little bit because the turbulence is changing and you can't necessarily perfectly keep up but it's basically done continuously and this is this is what you get from the same and the left is the same image that you saw before of the star and this is an image with adaptive optics much smaller much steadier and what this doesn't show is this also much higher intensity in the middle so why is that you have light that's spread over this huge area and you're gathering it together with your adaptive optics so it's just on 2 or 3 little pixels so the intensity of the light in those pixels is going to be much much higher and that's shown this different portrayal so here's the star we were looking at and here's what it looks like if I plot intensity in the vertical direction and X and Y in this direction on the sky here are these little speckles without adaptive optics and with adaptive optics I gather all this area together and put it into this actually three pixels here more or less and they become much brighter than the area than they would have been and that has a lot of advantages you can see more detail of course but also imagine you were trying to observe a faint planet around a bright star so here's a bright star and somewhere in here there's a planet and well is that the planet is that the planet is that the planet these speckles get in the way of figuring out how to image this planet but of course if you gather all the light from the star in a nice neat place you can easily see a planet over here or over here over here easy is kind of a relative term but you have it we have a chance of seeing a planet and there have been I think as of yesterday 26 planets around other stars that have been imaged by adaptive optics of course there are thousands that have been seen in indirect measurement methods such as with a Kepler satellite so here's an example of what this does for for planetary science this is an image of the planet Neptune and new for red light 10 meter tosco great big telescope largest optical telescope imaging optical telescope we have doesn't look like much here's with the hubble space telescope then that same infrared light much much more detail but Hubble is only a two point four meter telescope and if you look at it with a ten meter telescope that's that's corrected very well it ought to see see things four times better the ratio of 10 to 2.4 roughly and sure enough there's lots more detail on these cloud patterns that are on the planet Neptune and we've even used these clouds followed them as Neptune rotates to map out the whole rotate in pattern of Neptune's atmosphere here's another solar system object the planet Uranus with the Hubble Space Telescope and now I'm showing you two different wavelengths of light this is Hubble with visible light and this is Keck adaptive optics with infrared light and of course I cheated right you can't see infrared light with your eyes so what this what Larry Swarovski did when he made this image was to say this is I'm gonna color the short wavelength infrared light blue and the long wavelength infrared light red and just so I can get a good comparison between these two images one invisible light and one an infrared light and you can see we're doing quite well for ourselves ground-based adaptive optics you know large telescopes in the near-infrared has about the same resolution maybe even a little better than Hubble does in the visible and so there have been hundreds and hundreds of astronomical research papers published which used both information from Hubble and from adaptive optics on eight or ten meter telescopes to look at the same detail in two different wavelength bands and you can learn a lot from doing that well okay so how does all this work I told you that you change the shape of a mirror to cancel out the turbulence so this is like a zeroth-order approximation here's your deformable mirror here's the reflective surface and let's imagine that the incoming light has a way front that that should be flat if it's gonna be perfectly focusable to a point it should be a flat wavefront coming in and instead it's met up with some atmospheric turbulence which in this case of course I'm exaggerating and saying that it made a square or not just so I can explain myself a little better it's actually Wiggly in that square but what I've done here is I've made a notch in the deformable mirror that's half the depth of the nuts in the wavefront of the incoming light so what happens is when this whole wavefront bounces off the you're sending the part that's in front a longer distance to travel than the part that's in back the part that's in back only has to travel in and out to here or is the part that's in front has to travel in and out to here and I'm giving the the lagging part of the way from the chance to catch up with the part of the wavefront that was in front and arrange itself into a flat way front again now we all know that nature doesn't make square notches but it's sorry it's more or less the same principle so this is a cartoon of a deformable mirror think of a thin piece of glass think of actuators that are glued to the back but get long or in shorter when you put a voltage on them basically and there's a reflective coating and the part of the wavefront that gets in front here coming in is made to travel farther than the part that was lagging behind and so when the light bounces off the mirror is it's more or less of a flat wavefront that can be focused very well so this is a manufacturer's cartoon of what one of these deformable mirrors looks like here's the front piece of glass it's actually got in real life has a reflective coating on it these are these actuators which push and pull on the deformable mirror they're glued to the back now you all know from fooling around with glue at home that this is not necessarily a precision thing when you say in a precision field you've glued 4,500 actuators to the back of a piece of less you should worry because it's hard to get all the all the actuators glue curing at the same time if you did it sequentially the glue on the first actuator would be long dry before you've got the glue on the last actuator even inserted you have to think very hard about how to do this and then these actuators are based in a rigid baseplate so when they get longer and shorter they don't expand in both directions they're fixed here so they push and pull on the glass in front and for the 30-meter telescope EMT for short which we're hoping to build there are actually almost 5,000 actuators in the deformable mirror so this is really getting up there much much larger number than we've been dealing with so far well this is what a an deformable mirror actually looks like here's the front so the light comes in and bounces off you can see it's a mirror it's reflecting the pieces of this optical bench that are over here now here's the secret if you're being given a tour of a place that has an adaptive optics system and you don't have a clue what you're looking at because it's a big mess there are all sorts of optical components all around what you look for is an optic which has Julianne's of wires coming out the back now why is that each of these wires gives a command a voltage to one actuator which is going to push or pull on this little face sheet in front and so even if you have a mirror with only 400 degrees of freedom 400 actuators you're gonna see a cable coming out that has 400 strands in it and you can say oh what a beautiful deformable mirror you have even if you don't have a clue what but you were looking at I've done that don't tell anybody okay so there's a there's one hitch in this which is that you need a bright star nearby so if your favorite galaxy has a star close by it's fairly bright the light from it and the galaxies go through the same turbulence and you can do what we've just been describing but guess what when you look up at the sky at night it's mostly black right not too many stars considering that if you want to look at a random place in the sky where there's a galaxy that was born billions of years ago and this very faint so your eyes can't see it it's not going to have a bright enough star nearby in general less than 5% of the objects in the sky of the positions in the sky have a bright enough star nearby so the star in the galaxy typically will be too far apart this measurement of the turbulence will be fine if you happen to be looking in this term action but it will be useless if you want to look at your favorite galaxy because the turbulence is different so the idea that saved the day here was that if there's no nearby star you can make your own start using a laser now how does that work there are a couple ways to do it this is this is the way that we've been doing it at lick and Keck Observatory so it turns out that at a height of about 90 kilometers in the atmosphere there's a layer of atoms that comes from little micro meteorites burning up in the atmosphere as they streak into the atmosphere very fast they get hot from friction and they blade away and they leave their atoms up there and so there's a region there's a layer where there's increased density of sodium and calcium and iron lots of lots of other metallic like elements and sodium is particularly useful because it has a very strong resonant transition a spectral transition like those yellow streetlights that used to be all over the place those deep yellow streetlights then you couldn't tell what color your car was because everything was yellow so they're they're being replaced by LEDs but that think about that yellow color of light and if you shine that up on these Sony Madam's they remit into all directions and the directions that happen to go back into your telescope you can use to measure the turbulence and it is working quite well I have some anecdotes because in the 90s when this hadn't ever been really tried for astronomy I was physicists at Lawrence Livermore National Lab and they have a lot of expertise in lasers so they had lasers equipment they had people who are expert in using them and building them and they had what's called dye lasers from a program to separate isotopes of uranium to make fuel for nuclear power plants and a dye laser has the advantage that you can make it shine at any wavelength you just trickle it with with the wavelengths that you want to have it lays at and what comes out the other end is that exact same wavelength but much brighter so there was a whole building kind of over here relative to this office building at Lawrence Livermore National Lab which had nothing but lasers in it and it was being that light was being sent into an underground pipe to another building over here which was the lab building where they signed it on uranium gas and tried to make this isotope separation happen so we we sent our yellow light through the same underground pipe but we put a mirror down here in a manhole and just sent it up into this guy instead and it was quite a show this is a kilowatt laser and you could see it for 10 or 15 miles away and we had a little telescope here with which we looked at the sodium guidestar which was way up there and this is the pipe that sent it up into the sky I couldn't even follow a star it was just fixed but we wanted to measure this laser guide star spot in the sodium layer and used it to actually measure the turbulence even if we couldn't correct for the turbulence with with the system we had there were some amusing moments there first of all there was a freeway kind of over here and so my management at the lab said I had to meet the press and announce and explain what we were doing and announced to the Highway Patrol and the local police that we were going to send this laser into the sky a certain night so that if cars stopped in the middle of the freeway the CHP would could get out there and screw them along and so people didn't panic in the nearby towns and so forth so it worked quite well the police loved it eventually they sent a Highway Patrol person with the CB radio to be with us so they would know when we were about to fire the laser and they had they these radio communications with the rest of the police departments in the in the valley the Livermore Valley so my story is about UFOs there was a lady in Pleasanton which is about eight miles away from this every time she saw this laser go up she would call 9-1-1 and she would say there's a UFO hovering above Lawrence Livermore National Lab and it's sending down this laser beam and sucking up nuclear secrets and she did it every time we fired the laser so we would hear these these nice CHP officers next to us say oh no you know here's that lady from Pleasanton again but anyway that's my UFO story it's true so we we first built a laser guide star for Lick Observatory here's the old three meter telescope that has a new lease on life now because of this laser guide star and it's doing great stuff and then we built one for the Keck Observatory in Hawaii which is ten to ten meter telescopes that the University of California and Caltech and NASA jointly run and at the time this was considered to be sort of an oddball thing to do and a little bit far out but guess what now of all the telescope's are gone the summit of Mauna Kea they're all running these lasers so you can see but here's a bunch of telescopes each one is firing its laser and it's become a general in general use now for the largest telescopes in the world so I find that very gratifying and I'm now going to tell you a little bit about what we use this for to learn about the universe and I'm going to focus on this one area that I've been doing work in which is to study colliding galaxies so let's start out by saying what is a galaxy not everybody is familiar with the terminology a galaxy is a large system of stars and gas and it has usually several million to several trillion individual stars bound together by the joint galaxies of the star and Dark Matter that's that's you know in a halo in them toward folk centered on the middle of the galaxy so there are two there are three main kinds of galaxies spiral galaxies like the Milky Way or Andromeda elliptical galaxies and ratty little irregular galaxies which can which are typically much lower mass and look like they've had a train wreck recently and they're one of the very interesting areas of research that's a whole story in itself but I'm gonna focus on what happens when two of these gas-rich spiral galaxies collide and I think I mentioned that all at least these two kinds of galaxies virtually all of them of a decent size have a big black hole in their core it's not so clear if these little guys do so I have to start out by telling you a little bit about what is a black hole everybody seems to know here's a National Post energy spewing black hole puts on cosmic show for astronomers that's not what a black hole looks like but it makes a great sales pitch it's a region of space so densely packed with matter that nothing not even light can get out so these are the densest places in the universe to give you a sense of scale if you took all the matter in the earth and squished it down to the size of a grape this would become a black hole these are really dense and so how big is a black hole in space here's here's your grape phenomenal one inch great if you took them the Sun or another star like it and squished it down to three miles in diameter it would be a black hole if you took a thousand suns and squished it to three thousand miles the size smaller than the earth but not a whole lot smaller that would be a black hole and if you took a hundred million Suns and squished it to an eighth the size of our solar system that would be a black hole so just that's just for scale and as I said black holes are the densest things that we know in the universe and here's a here's a cartoon to try and explain that not even light can escape from a black hole and that's where the name came from so if you imagine that you're on a planet like Earth you know that if you throw a ball up in the air eventually it'll fall down again from gravity from the Earth's gravity the mass of the earth pulls it back if you imagine in each of these circles you're adding more and more mass you if you throw the ball up with the same amount of force it'll fall down quicker it won't will turn around at a lower altitude and fall back to earth and if the gravitational pull is so big that not eat not only your not your ball but even light can't escape then that that is when a black hole has formed so back hole is so compact and dense that the escape velocity is bigger than the speed of light and we know that things can't travel faster than speed of light so light is stuck in in the region of the black hole well we want to actually look at the reasons around the black hole and and get a feel for how they're going to evolve when these galaxies collide so how do we actually see black holes today of course no light comes from the black hole this cartoon says it's black and it looks like a hole so I'd say it's a black hole but that doesn't get you very far so we want to be able to actually say things about what's happening in the immediate vicinity of a black hole so this is a cartoon showing the very inner regions of a galaxy there's a supermassive black hole maybe a hundred million or a billion times the mass of the Sun it's too small to see even in a cartoon but there are hot gases around it that are slowly spinning around and spiraling in and falling on this black hole and as they fall in they get hotter and hotter they emit x-rays farther out they emit visible light infrared light and since this is a spinning disk if we're looking at this side of the disk the light light approaching us will be blue-shifted it'll become bluer than as emitted wavelength and light on the other side which is moving away from us will be redshifted and if you haven't thought about this too much it's like the Doppler shift of the horn of a train so after you're standing here and a train is going by when the train is in the distance coming toward you you'll hear the two toot of the horn happening at a higher pitch and after it's going away you'll see it happening at a lower pitch that means that the wavelength of the sound is getting longer for the train going away from us and shorter for the train coming toward us and it's the same thing with light so to try and measure for example the mass of the black hole we can measure how fast the material on this side is coming toward us and how fast the material on that side is going away from us and if the black hole is more massive of course the disk will be spinning faster and faster so another terminology point a galaxy core like this with an accreting central black hole or matter is flowing onto it it's called an active galactic nucleus so I may mention the word AGN and that's just think of this picture when you hear me say a GN okay so how does adaptive optics help to see black holes or to see the regions right around them we want to see this region very close to the core of the galaxy we want to measure how fast the gas and stars are rotating around the black hole to weigh it to measure its mass and since we need to see things very close to the black hole we need very sharp images so that's where adaptive optics comes in you can see things that are quite close to a supermassive black hole now I said I'm particularly interested in colliding galaxies these are just to convince you that galaxy collisions do happen these are some Hubble Space Telescope images of colliding galaxies mergers between galaxies it's usually looks like a train wreck after a while like a billion years or so these train wrecks will settle down and they'll become boring elliptical galaxies as I showed you many slides ago but for when they're in this phase they really are producing fireworks in lots of loose gas that can spiral into the black hole and make it shine so it's now known that the size of a black hole is correlated with the characteristics of the galaxies as well I don't have time to go into detail on that here is a scenario that was put forth by Dima Dima Te'o and colleagues in a computer simulation here our simulation simulated two galaxies that are going to collide and they get closer and closer they eventually do collide a lot of this gas falls into the black hole and the black hole starts emitting x-rays and gamma rays and an ultraviolet light like crazy and it's emitting so much light that it actually can drive out a lot of the gas that's originally in these galaxies and so a couple of million years later billion years later you'll just have the stars lying around left over from this collision most of the gas will have been pushed out by the emitted admited radiation from the black hole it's a hypothesis it seems in some cases to really apply very well but we don't know if it applies only to the brightest active galactic nuclei which are called quasars does it apply to weaker ones can we see observational signatures and what happens if the black hole isn't accreting a lot but we know it's there we can measure its effect on its surrounding so that's those are the general questions which we're interested in answering so for the work I'm describing here we looked at a sample of nearby gas-rich galaxies that had had recent mergers so that the two nuclei the nuclei of the two galaxies are close together now you have to think close on an astronomical scale so close in this case is within three thousand light-years of each other that's that's close and these are galaxies that are forming stars like crazy because there's lots of gas around so they're very strong emitters of infrared light and so their names are ulirgs ultraluminous infrared galaxies so if I refer to ulirgs that's what I'm talking about and we're looking at them with the Keck telescopes - Keck telescopes adaptive optics systems so here's an example this is a galaxy named NGC 6240 it's a merger of two gas-rich galaxies this is the gal this is what's left over of the merger it's still in the trainwreck stage it's relatively nearby 300 million light years that's nearby you miss lots of x-rays in the infrared light it's got a double nucleus you can't quite see it here but I'll show it to you in a minute and it's got these big tidal tails which I'll try and illustrate why they happen it also fortunately has a bright star nearby and so we can use either this star or a laser guide start to do adaptive optics correction and look in the middle and we're going to look in a minute at the double nucleus but I want to show you a computer simulation done by Josh Barnes of how a galaxy might end up looking so disheveled with summer city so here's a simulation of two galaxies that are going to collide they pass each other by but all the gas is being ripped out as they do that and they go into orbit around each other and what's left is these big tidal tails and that's that's what this galaxy that I've been looking at yes so we're gonna zoom in now on the nucleus here here's Hubble's picture in visible light here's Hubble's picture in infrared light so now you can see the two nuclei for sure and here's kext picture in infrared light lots more detail one thing you can see right away is all these little bright emitting regions each one of those is a newborn star cluster was only born ten million years ago with lots of young stars so these collisions also make young stars like crazy and the question to ask ourselves is we've got these two nuclei I told you there were two black holes here you can see them in their x-ray ignition where are they is that the black hole is that the black hole is that the black hole is that the black hole you know if we want to learn what's happening around the black hole we first have to figure out where it is so we can look a little more closely here I've blown up the image of each nuclei nucleus that didn't help right I mean where's the black hole so fortunately in in many cases you can get information from other astronomical observations other types of astronomical observations and in this case each of these two nuclei was emitting radio emission that's completely characteristic of what is seen from these disks around black holes and so we can use the radio emission here's the North nucleus here's the South nucleus the we know these are coming from regions right around the black hole they have a very characteristic spectrum and superb spatial resolution unfortunately unfortunately Gallimore and Bestwick made this image in radio emission at a frequency of 5 gigahertz and so what we can do is just plop down the contours from the radio emission on our two nuclei that we can see a Keck with adaptive optics and this one falls right on one of those point sources in the North nucleus this one is actually a little farther north than we would have thought and it turns out there's lots of dense dust in this region and it's hiding the black hole even an infrared light but now that we know where the black holes are we can start asking questions like how fast is the gas spinning around the black hole and using that information to measure the mass of the black hole so how do we do that we are using something called an imaging spectrograph the name of the spectrograph is osiris so what is a spectrograph a spectrograph measures a spectrum which is the light intensity as a function of color or wavelength of light and an imaging spectrograph is actually a series of images and and it's you can get an image of a galaxy in blue light and then a gallon in the same galaxy in green light the same galaxy and yellow light the same galaxy and red light or another way to say it is you have an image of the galaxy and at each pixel in the image there's a whole spectrum of light that's coming from the galaxy at that exact place now why do we want to follow the colors of the light because we want to measure the Doppler shifts of the spectral line so remember I had this picture of a disc and I said that you can measure how fast this part of the disc is moving toward us by measuring how much bluer the light is on this side then it started out and you can measure how fast material on this side is going away from us by measuring how much redder it is and so that's exactly what we're going to do and the shift in wavelength of light is directly related to the velocity at which the gas in this case is traveling here C is the speed of light the change in wavelength divided by the wavelength is the change in velocity divided by the speed of light so it's very straightforward and here's one way to portray the data so this is X&Y on the sky here's the data here's a model and it's color-coded so blue is material moving toward us and red is material moving away from us this is a model this is the actual slightly Messier data but you can see there's the black that the position of the black hole in this case and by looking at the patterns of this motion of the gas around the black hole we can measure its mass and in this case we use two different methods and it's about one to two billion billion billion times the mass of the Sun so these are big hefty supermassive black holes and now that we know their mass we can try and make sense of many of the other observations that are telling us about the region right around the black hole and I'll tell you about this what that is in a minute so just a quick summary of what we found we can locate where the black holes are we can measure their masses by mapping the velocities of the gas and stars that are zooming around them spinning around them these guys really are supermassive a billion times the mass of the Sun that's getting up there I think the record is about 10 billion times the mass of the Sun so we didn't in this case we didn't hit the record but there are lots of heavier ones and the next question we want to think about is will these two black holes each one brought in by one of these galaxies ever merged together and if so as black holes merge they emit huge amounts of gravitational radiation gravitational waves I'll try and touch them touch on that very very briefly because those waves have now been seen so one of the things that can influence whether these black holes here's another computer simulation here distant galaxies there's they're going around each other and in this case there's lots of gas lying around and they eventually do spiral in and merge but if there were no gas in the nucleus there's this famous thing called the last parsec problem a parsec is 3 light years it's a astronomical measure of distance so if there's no gas in this central region here you can end up in a situation where the two black holes are just spinning around and around each other forever and since there's nothing to slow them and have them lose angular momentum and get closer and closer together they're just stuck so this is called the last parsec trouble they would just spin around forever and it's been shown in simulations like this that if there are giant gaseous disks around the black holes in the middle the black holes can slow down by by technically it's not quite friction but friction with the gas they get they move slower they lose angular momentum and they actually can hurt so we started out to say okay well we can see this region very well we have high spatial resolution with adaptive optics let's see what happens are these disks there and it turns out they are 417 galaxies that we looked at as of a year ago there are big nuclear dissin all of them their radii up to about 2,000 light-years they're moving at hundreds of kilometers a second in rotational velocity in most cases there's so much gas that their visit vigorously forming starts and that has interesting implications so two binary black holes can lose angular momentum in several ways one of them is they can scatter off stars in the nuclear region and just slow down because each time they scatter off a star they go a little slower and if they but they may have kicked out all the stars around them in which case they get stuck in this last parsec problem and we want to ask not only can they be slowed down by gas but what about stars can they can we somehow Rhian jects tars into the nucleus so if we have a reservoir of gas from these big central disks the gas can get in and slow them down so the black hole down but they can also start kicking stars randomly into the nuclear regions so the black holes can slow down by scattering off the stars as well as scattering off the gas so we think we've come a pretty good way to showing how these supermassive black hole can eventually merge and this last parsec problem is a great theoreticians problem but in real life life is messy as you saw in these pictures and we think it's not that big of a deal so why do galaxy collisions matter well it turns out we're gonna have our own galaxy collision we have the Andromeda galaxy right now is pretty far away but people who study the relative motion of our Milky Way galaxy and the Andromeda galaxy predict that in a few billion years we will actually our galaxy will be colliding with the Andromeda galaxy so this isn't something that you should stay away at awake at night worrying about but it kind of wakes you up to think that we may actually crash into each other here okay so I want to now go on to the secret extra slides which is to use adaptive optics to image the living human retina so people studied how the eye works for many years by taking dead animals I'm sorry about this but that's what they did they cut out their retina and they studied the retina after it wasn't able to see anything obviously and how much better it is to actually study the retina as it's functioning and be able to use adaptive optics both to learn about how vision works and also for medical applications to look at what retinal disease does to the configuration that you can see in the retina so the first thing you should be asking is why don't why do I even need it after of optics to look at the retina my doctor takes looks with that funny gadget in my eye and presumably she's looking at the retina and what's the big deal well it turns out that I'm sorry for the crudeness of of my cartoons but I've been told by my ophthalmology friends that this isn't too bad of a representation you know you have the white of your eye and then you have in the middle you have the pupil which is where the light gets in and at the edge and there's a lens that focuses the light on the retina and it's it's in the region around the pupil and at the edge it's attached to the rest of your eyeball so you know in bright light the pupil is much smaller than the size of the lens see when you go outside and you're all dazzled by bright light your pupil gets small so it won't let in so much light that you're unable to see anything but at night or when the doctor gives you that annoying eyedrops which they do in order to see your retina in the incoming light passes through these regions at the edge of where the pupil where the lens and cornea are attached to the rest of the eyeball and that's not perfectly engineered so to speak this is not a perfect attachment there are optical distortions at the edges of where your pupil is attached to the rest of the eyeball and literally when the pupil gets big at night or when you have those drops you're uncovering the optically bad imperfect attachment around the edges of pupil and you're looking through it so the results are poor night vision how many of you at night when you're driving look at see flares around street lights or halos around incoming oncoming car headlights it's very annoying that's because you're looking through this imperfect attachment of your pupil to the rest of the eyeball so it's annoying for us to drive but it also means that the doctor or the researcher can't image the retina very clearly if they're looking in through that distorted region as well and so that's where adaptive optics comes in this is actually pretty bad the these are perfect eye what a perfect eye would see as the pupil goes from being very small only a millimeter across to wide open seven millimeters across so a perfect eye would see things more and more clearly better and better spatial resolution as the pupil gets bigger it's like with a bigger telescope you see you're supposed to see more clearly but that's not really what happens here's what happens so as the pupil opens up you're looking through more and more of this imperfect region in your eye and the image of a point source gets worse and worse and so what adaptive optics is doing is trying to take you from this sort of ratty image of a point source up to what it really should be if the optics in your eye were perfect so this started out being kind of a clumsy way to do things here's adaptive optics systems this adaptive optics system looked exactly like the ones we used for astronomy this is like twenty years ago note the size of the computer but the point is you can put a human being here looking into an adaptive optics system and have a camera that takes a picture of the retina and get much better images of the retina than you could before nowadays these things are like that big but they're so crowded with optics that I couldn't show you what the details are so I pulled out this old picture to be able to explain better so here's a retinal image this is without adaptive optics this is with adaptive optics you can see individual color photoreceptors called cones these are what detects the color light this is the shadow of a blood vessel the blood vessels are in front of your retina and you can even get the 3d structure of the retina and add exquisite spatial resolution that retinas pretty thick and you can look at every this is just looking at one layer but you can look at every layer in the retina in great detail including the nerves and the blood vessels and lots of other good stuff you can also ask what about color vision what each of these cause is sensitive to a different range of color we have red cones green cones and blue cones meaning they're sensitive to red light or green light or blue light and it turns out that perfectly ordinary people with with perfectly normal color vision as measured by your eye doctor or by those annoying charts that they show you so these people have normal color vision and look at this this guy this person who I don't know if it's a guy or a woman has far fewer red sensitive cones than this one about the same number of blue sensitive cones and way more green sensitive cones than this person yet they would both look at a wall of a white wall white light is made of all color so you're looking at all colors of light on a smooth wall and they would see a smooth wall they don't see blotches green blotches and red blotches so this is fascinating it means that your brain is doing lots of practicing and smoothing and interpretation of what your complicated color detection system in your eyes is sending to it and there's lots to be learned here I want to close with a movie I said that you could image you can image with adaptive optics blood vessels so here's an image of capillary and you can actually see the white blood cells zooming through this capillary I love this it's squirming now we know how to stabilize these images better but when when Austin were to first discovered these white blood cells he had a grad student who he told to count the white blood cells as they went through because he thought they could use it to characterize how healthy the capillary was if capillary was blocked you wouldn't see so many going through in a given amount of time so unfortunately they don't do it that way anymore but this grad student got a great PhD thesis anyway that's the end of my talk I don't want to thank you very much and if you'd like to learn more about how you can support UC observatories and adaptive optics Natasha is sitting right here is the person to contact and thank you this is a great audience I'm gonna make a sociological question comment first which probably will get me in trouble why is it that men always ask the questions and there are no women in line okay now I've put my foot in my mouth and I will extract it and anyway I encourage women to ask questions to know answer that question dad I've been wanting to know the answer to this for a long time which is okay so we're in Silicon Valley we used to have these things called hard drives and they would move that's a great that's a great question first of all you can use LCDs as deformable mirrors what the LCD does is changes the index of refraction in each pixel so you can actually slow down and or speed up the wavefront the problem is that they tend to want light of a single color and astronomers are greedy they want to go all the way from the ultraviolet and their relatives they're too slow right now so they've been getting faster but northern mechanical yeah yeah you have to these are what's in these it's pixel is these long molecules and they have to reorient it just take some time yeah so ideally what you could do is have a perfect detector measuring the way of measuring measuring the wavefront look at the star and or maybe just look at your object that you're imaging and if you can take an image faster than the turbulence is changing you ought to be able to use software afterwards to reconstruct what all that turbulence did to your image and that's called speckle imaging and it it works but unfortunately we don't yet have noiseless detectors so you have to be reading out a thousand times a second every time you read it out engine noise into the image so you have to be looking at a really bright star or something a bright source so we did this many years ago for the planet Neptune before our adaptive optics system was working and it worked well but Neptune is very bright and if you want to look at a faint galaxy at the other end of the universe you can't do it that way yeah good question yeah my question is similar what kind of response time adaptive system has and I understand they're getting faster and faster and also would like to ask what the characteristic times of the atmospheric perturbation I understand there are several modes and what kind of modes and maybe you may not correct for all of them yeah all good questions so I'll give a practical answer we have to run the Keck adaptive optics system doing the measurements 500 times a second and we think that's a little too slow we should probably be doing it a thousand times a second of course it changes from night to night because the speed at which the turbulence changes is partly determined by the wind that's blowing at turbulence across your telescope so on a windy night you'll have to go faster than on a still night what was the second question like moans oh yeah good so if you if you you can decompose all the junk that the atmosphere puts onto your image of the star say into various kinds of perturbations of the of the wavefront and there are big ones that that just change gently over the mirror of the telescope and there are very short wavelength ones which change many times across the mirror of your telescope and the big ones tend to change more slowly than the little ones so an adaptive optics system typically only tries to correct up to you know they they correct all the slow ones and some of the medium ones and none of the really jiggly little ones and and if you want to do adaptive optics at shorter and shorter wavelengths right now we just do the infrared if you want to go into the visible you have to correct even more of these small scale modes which means your adaptive optics system has to run even faster than a thousand times a second so it's the modes are related to how fast you're going to run your video system all right thank you over the years of hearing discussions like this they always talk about a lot of gas circling a star or what have you I've never heard them actually talk about like what density how many molecules per cubic meter or how is it measured when it is considered a lot of gas in that environment okay it's all relative none of these densities are what we would call high in the Earth's atmosphere is one of the xix molecules per square centimeter that is extraordinarily high for astronomy and maybe in the innermost parts of one of these accretion discs you get up to that but mostly the creation disk is much less dense than that and in the matter between the stars it's more like dances like a hundred molecules or atoms per cubic centimeter and low-density is like 0.1 so there's not much matter out there thank you space is big and there's not that much out there yes how close does current al get to the diffraction limit I'll say a 10 meter telescope at visible wavelengths so the diffraction limit is just what a perfect telescope would see if there were no turbulence and right now a CAC in the infrared at a wavelength of 2 microns we can get quite close to the diffraction limit we've got a nice central peak lots of good stuff in the visible not so much so I think there's a there are two air force telescopes that have very fancy adaptive optics systems that can do adaptive optics in the visible but even they struggle a bit ok thank you what was the time frame out that when you're doing experiment it's out there Lawrence Livermore yeah I want to say the early 90s is that mid 90s something like that for galactic core collisions and we've done the measurement of the neutron star collision with the LIGO and I'm wondering what the potential is using light go to measure this object yeah I was I was hoping you would ask so gravitational waves which are these distortions of space-time the the wavelength of the gravitational waves depends on the mass of the black holes is going to merge so the ones that the LIGO interferometer --zz have measured these are big installations in Louisiana and Washington Italy and now India and Japan they have measured mergers of black holes that are tens of solar masses 10 tens 30 times the mass of the Sun if you want to look at mergers of black holes that are thousands or ten thousand times some intermediate-mass black holes you have to use this Lisa which is a space gravitational wave interferometer same principle as the ones on the ground but in space and there's the the different parts legs of the interferometer are separated not by a kilometer but by a million kilometers and so they can look at much longer wavelength waves that are much lower frequency that's changed more slowly and if you want to look at these supermassive black holes you can come back to earth and you can have an array of radio telescopes all around the earth called a pulsar timing array each of these radio telescopes is timing the pulses from a pulsar a neutron star in the local neighborhood of the earth extremely accurately and a very long wavelength gravitational way that's so long that it extends farther than the distance of two pulsars from each other you'll see the timing of the Pulsar changing relative to each other as the wave goes by and unlike this space-based interferometer which is going to go up in 2035 or something these this pulsar timing array is now called the International Post our timing array it's got telescopes all around the earth and they're getting pretty close to being sensitive to billion solar mass black hole mergers I wouldn't be too surprised if in the next couple of years they saw one so when you get down below a billion it gets harder but we're getting close thanks very much for indistinct talk dr. max I was wondering are there relative advantages and disadvantages to having the adapt the the surface that is active to having it be the primary versus a secondary mer yeah good question so in principle you'd love to do this with a big primary mirror telescope but they're heavy so even the Keck telescope which has hexagonal segments that are about that big across their segments are about that thick and so you're not going to be able to bend them in any realistic way that if you were to bend then the fourth that you'd have to apply is so big that they'd probably break the glass but what you can do is the light comes into a conventional telescope it bounces off the primary mirror and goes up to a secondary mirror and then comes down again to your instrument and people aren't making adaptive secondary mirrors and there are several big telescopes that have them and a bunch of us are eager to put them on the Keck telescopes and on a thirty meter telescope so I think that's going to be the next ten years story is these adaptive secondaries and those are right now the biggest ones are 900 millimeters across so a little bit less than a meter across thank you yeah they're nice so I think you may be partly answered my question but I'm really curious how you make the adapters in here it's like how thin are they and how do you ensure that yeah so you have to bount you people do these calculations before they go out and build on of how thick it should be as a function of how much you want it to move up and down in a local place so if it's too thick you'd have to push really hard on it in order to make it rise a certain amount and that puts stresses on the glass and also it means that if you push in one place you'll be moving the mirror relatively far out if you make it too thin and you push on it you'll just get a very local region poking up and then the rest of the mirror won't even know that the actuator has pushed so that you have to balance the thickness with how far the what's called stroke is gonna be how far each actuator has to move and how far they apart they are so there isn't any one answer for each deformable mirror that gets built somebody's out there doing the engineering of how do you balance those different things good yes well what'd happen if black holes collided with like one of them sucker one of them just keep closing in closing in and closing in closing in yeah it's a good question so if you have if you have a small black hole and a big black hole merging you could you could say that the big black hole sucks up the little one and gets a little more massive and it's one big black hole if it's two equal mass black holes it's it's not so easy to describe in terms in the terms that we would use from day to day but they do merge together and form one that's twice as big so yeah they really merge unless they get stuck going around around each other forever we think that doesn't happen yes I had a question about your inept I think it was your Neptune image huge images you showed earlier can you pull those up is it possible to pull might have been Jupiter but I think it was nothing okay tell me when to stop this is Uranus that's enough - yeah this one right here okay was curious about is I think so it's thing that's the objective optics on the far right yeah and the center one was the Hubble image yeah but it looks like there's a contrast difference so ya see the polar caps with a little bit but you get it seems that more contrast you can't see the polar caps the adaptive I wonder if there's a contrast issue with ah or do you get better contrast or yeah for contrast different so the reason this is black romo sorry the reason this is dark and this is darkest because methane and the atmosphere is it low in the atmosphere is absorbing the light of the Sun so this is all reflected sunlight and if there are no high clouds the fun light goes deep into the atmosphere and gets absorbed by methane and what these are high clouds so the light gets reflected before it ever goes through all the methane and has a chance to get absorbed so the contrast is higher here it's like that picture I showed you of one star toward the beginning of the talk where you gathered all these little ratty looking speckles together and got a really sharp peak and that made higher contrast so you're this light here is actually coming from these bright regions and it's just not all getting collected in one narrow place because it's only a two point four meter telescope but the spatial resolution right same thing here are they capturing the same wavelengths yes take to form a black hole okay so there are many ways you can form a black hole that the most immediate one is to take a massive star and it reaches the end of its life and it blows up and the central part of the star falls in and makes a black hole because it doesn't have any way to support it so it doesn't have any pressure anymore and so it just keeps falling in and in and in and eventually the light can't get out but there also we think black holes that were started at the beginning of the universe and that grew bigger and bigger as billions of years went by and probably lots of other ways to form Superman big black holes as well and one of the big questions is if all the black holes early in the universe were relatively small how did they get to be 10 billion solar masses that's really big so they're more there are a lot of collisions that it did that suck in on these intermediate-mass black holes it's it's not well understood it's a good question to ask okay one more one more telescopes that are out in space like Hubble don't have this problem as I understand it is that true so the James Webb Space Telescope which is six and a half meters across instead of 2.4 meters Hubble is made of segments and so segments can be a little bit floppy especially in space the supports kind of float around a little bit and so they have what they call active optics which is they're always measuring where one segment is compared to its neighbor and so they do the measurements and and web was designed a long time ago so they measure it they send the measurements down to earth there's a computer and a human on earth who tries to figure out what the actual positions of the segments should be and then days later they send the signal back up to the telescope about how to readjust the segment positions so that is that is adaptive optics but as very slow and you can imagine if they were making 20 meter telescopes in space you'd have to really do that quite a bit hopefully under question I'm trying to get out I guess to understand is it seems like there's a trade-off between the cost of putting a telescope out in space versus the complexity of trying to do adaptive optics on earth is there some point at which it's just better to go out in space and spend the money with rocket ships and do it that way there there isn't it and that point evolves with time so I guess the current thinking it's not quite clear where the line is you know where is that point that there's a new generation of 20 to 40 meter telescopes which people want to build they're called BLTs extremely large telescopes and today there's a general consensus that you just could not do that in space it's you'd have to assemble things in space or make segmented mirrors that unfold many times as opposed to James Webb which only unfolds once and it's just beyond us that's not to say it's always going to be beyond us maybe you know I wouldn't be too surprised if we're doing it in 30 or 40 years but right now that's the line is sort of short word of 20 meters and people aren't talking in NASA about launching eight meter telescopes 10 or 12 years from now and I think it's sort of up in the air whether they'll be adaptive up at adaptive or not active or not thank you yeah thank you very much thank you light I wanted to say that for so many years people on the ground have had an inferiority complex compared to space-based telescopes and you've been a one-woman therapy session for all the ground-based astronomers so thank you for all you do and thank you all for coming [Applause]

Channel: SVAstronomyLectures

Views: 13,667

Rating: 4.877193 out of 5

Keywords: astronomy, science, astrophysics, science news, optics, adaptive optics, galaxies, colliding galaxies, Claire Max, Lick Observatory, observing

Id: stAGLke6XDU

Length: 76min 2sec (4562 seconds)

Published: Tue Oct 30 2018