New Worlds and Yellowstone: How Common Are Habitable Planets?

good evening everyone my name is Andrew frat-boy I'm the astronomy instructor here at Foothill College and it's a pleasure for me to welcome all of you here in the auditorium and watching and listening on the web to the ninth annual Silicon Valley astronomy lectures here at Foothill College these lectures are sponsored by NASA's Ames Research Center the Foothill College astronomy program the Astronomical Society of the Pacific and the SETI Institute and we're very grateful for the support of all these organizations to make these dynamic introductory talks in astronomy possible tonight's talk is by dr. Jeff Marcy of the University of California Berkeley dr. Marcy is the world's leading planet hunter having with his team found more planets than anyone else in the world and in history he is professor of astronomy and director of the center for Integrative planetary science at the University of California at Berkeley and he was one of the youngest scientists to be elected to the National Academy of Sciences our most distinguished national body of scientists among his many honors he has won the Shah prize and was the California scientist of the year in 2003 what's especially exciting for me about dr. Marcy besides his work is his very strong interest in education and public outreach he teaches introductory courses at Berkeley he gives many public lectures around the world and devotes a lot of time to sharing his work with the public at large including his website exoplanets dot-org to explain his work he's appeared on many national and local television programs including the David Letterman Show if he can survive that he can survive any NASA or NSF board he was also the first speaker we ever had when we got these lectures started after nine years it was high time to welcome him back for me this is like being able to introduce Columbus or Magellan or Captain Cook someone who aspired new worlds that none of the rest of us have seen and can tell us in person what it was like so ladies and gentlemen it is for me both a professional privilege and a personal pleasure to be able to introduce to you discussing new worlds in Yellowstone how common are habitable planets dr. Geoff Marcy our universe as you all know is expanding and indeed accelerating and it contains exquisite beauty that brings many of us here tonight and of course the universe also contains extraordinary and baffling mysteries the universe we now know consists of dark energy dark matter and a smattering of luminous owaisi's we all call galaxies in fact we live in the Milky Way galaxy as all of you know and our Milky Way galaxy is itself an enormous place with spectacular mysteries the Milky Way galaxy contains 200 billion stars or so and it's a hundred thousand light-years across which means that traveling at the speed of light a laser pointer or a flashlight the beam would take 100,000 years to traverse the length of our Milky Way galaxy so it's an extraordinary place this galaxy of ours but what I find most compelling and I think intriguing about our Milky Way galaxy is that the laws of physics of chemistry of mathematics that we all learn as schoolchildren apply equally well everywhere within our Milky Way galaxy the laws of gravity electricity magnetism quantum mechanics even and the constants of nature are the same from one end of our Milky Way clear across to the other side and indeed within our entire universe of hundreds of billions of galaxies like our Milky Way the laws of physics and chemistry and math also equally well apply and that tells us something profound I think and indeed beautiful which is that the physical properties of our world the earth our solar system it's the Sun and the contingent of planets probably has properties that are duplicated elsewhere within our Milky Way and the universe at large that is the physics and chemistry of our earth are no different than the physics and the chemistry that apply everywhere else and so we might imagine that there four planets like the earth solar systems like ours might exist elsewhere within our Milky Way galaxy and beyond what we don't know however is whether there are comparable laws indeed universal laws of biology you might ask yourself is there one equation of biology that you learned in high school that you can write down that assuredly applies throughout our Milky Way galaxy and beyond and I would suggest to you that we do not have any such knowledge even conceptually of rules laws principles of biology that we are sure can apply elsewhere so we are remarkably ignorant in the field of astrobiology and in particular there are some questions of biology that you might ask whether or not they indeed pertain throughout the universe one is whether or not liquid water is a prerequisite for life as it seems to be here on the planet Earth you might also ask whether or not the organic molecule that codes for the structure of one generation after the next and to the next DNA is the only organic molecule that can perform this function or whether in fact there might be other molecules that can serve to code life from one generation to the next finally the question of biology that intrigues me the most and perhaps you also is whether or not intelligence is really the pinnacle of Darwinian evolution or whether or not we human instead represents some twig on the evolutionary tree some flew some lucky throw of the dice that occurred on the East African savanna two million years ago allowing the early hominids to become bipedal develop big brains and dexterity so that someday they could write symphonies and build rocket ships we don't know whether intelligence is a normal outcome of evolution in general and certainly throughout the galaxy and the universe so our ignorance of biology is a little embarrassing maybe profound and of course it stems from the fact that we still to this day here in 2008 have only one example of life within our universe and it's the example right here on earth where all the life is based on DNA and so therefore we can't generalize any laws of biology without more examples to draw from and of course we are looking for other examples of life elsewhere in our universe notably just within our solar system the Sun and the eight major planets we have already sent spacecraft to all of them indeed one is about to arrive even at the the recently demoted Pluto and it will search I'm sure for some hints of any life there I'm not very optimistic the remarkable bottom line that all of us know is that despite the great exploration of our solar system that has occurred since the 1960s we still to this day have no evidence of even microbial life never mind advanced life anywhere within our solar system most excitingly I think we will continue to send probes to Mars especially just near the edge of the polar caps where some liquid water might exist perhaps subterranean giving life a chance still there on the planet Mars and in a few other venues within our solar system but I have to report to you to be honest I believe there's no chance of advanced intelligent life anywhere with our solar system there's just no sign of it at the present time and I think we would have seen such intelligence if it were there so we have to look elsewhere to find out what types of planets and venues might be suitable for intelligent life elsewhere in our universe and so I'm going to launch ourselves into the Milky Way galaxy with its 200 billion stars and tell you what we've been trying to do we meaning astronomers in general to get a handle on habitable worlds elsewhere in our galaxy the way that we've been successful so far in detecting planets around other stars is shown in this movie we can't actually see the planets directly even with the Hubble Space Telescope they're lost in the glare of the host star so instead we punt and watch the star itself and you see that stars actually wobble in space as they are yanked gravitationally by the planets going around them so this star in this animation is wobbling around with a reflex motion because the unseen planet is pulling gravitationally as it orbits we should be able to see that motion of the star in response to the planet and the way we do it is to use an effect that all of you are familiar with the Doppler effect in the Doppler effect as you know if you're standing next to a train tracks you hear the train whistle change its pitch you hear the train sound like this you can tell even with your eyes closed that the train is a common or going from the change in the wavelengths of sound as the train comes at you compressing the sound waves and then the train recedes away from you stretching those sound waves and so it is with light waves we can actually watch light waves as a star is coming toward us or away from us and watch the light waves change their wavelengths retching and compressing as the star is a coming and going and we see it in the form of the colors of the rainbow the wavelengths of white light shifting from the blue and to the red and back to the blue again we can actually detect this at the back of a telescope and that's in fact exactly what we do if we can do this then you might have imagined asking well could we detect the wobble of our Sun due to the planets going around our Sun yanking on it and the answer is yes our earth pulls gravitationally on the Sun just as we all learned that the earth is held to the Sun by gravity Jupiter of course Yanks on the Sun even more strongly being a bigger planet and so if you were to make measurements from Tau Ceti of our Sun you would make a graph as shown here the velocity of our Sun measured by the Doppler effect over the course of time 1960 1970-1980 up to 2020 and you would indeed see that our Sun is wobbling changing its velocity high low high low high low with about a 12-year period from one peak to the next 12 years is in fact the duration that Jupiter takes orbiting the Sun once as it does so the Sun does a little Irish jig in space in response and of course you can see that these waves here this change in velocity is not uniform some of the peaks are higher than others and that's because there are the other planets in the solar system also yanking on our Sun and so from a distant star you would be able to infer the presence of the planets orbiting our Sun from the effect they have gravitationally on our Sun so that's the game to play measure the Doppler shift and look for this reflex velocity of course to do so you need the world's largest telescopes to gather the light to measure this shift we are lucky to have access to some indeed of the world's largest telescopes Lick Observatory I hope many of you have visited it's visible from here at Hill College right up in the hills east of here on Mount Hamilton you should all visit if you haven't been to Lick Observatory a real gem of a science institution right in our midst there's also a southern telescope we use the anglo-australian telescope from which we can search for planets around southern stars not visible from the northern hemisphere here and then finally we're lucky to use the world's largest telescope the Keck telescope located on the Big Island of Hawaii perhaps you've been there as well it's located high atop a hopefully dormant volcano called Mauna Kea so with those three telescopes we are searching for planets but the real gem in hunting for them is the spectrometer at the back of these telescopes we remove the eyepiece and replace it with a 10 million dollar set of optics shown here schematically at the back of the telescope right here the light comes down originally white light and it gets spread out by a spectrometer into all of its composite colors or wavelengths of light and it comes to a focus at a digital camera at the back we record the spectrum of colors and it looks like this at the telescope this is exactly what we see at the telescope all the colors of the rainbow from any stars original white light and you can even see some dark areas where the light from the star has been absorbed by atoms and molecules in the atmosphere of That star now this is the digital camera image of the spectrum of a star and the Doppler effect looks like this if you come back a month later to the telescope you might see the spectrum shift another month later perhaps shift again another month shift again if the star is really being orbited by a planet the planet turns the corner and goes the other way and so the shift should go back and over and over again repeat in a periodic way showing you that over the course of months and years there is indeed a planet orbiting that star yanking on the star causing it to do all of this now let me take a moment and tell you that I have fibbed a little bit the actual amount of Doppler shift is something like a hundred thousand times smaller than what I just showed you these dark spectral lines of which you may be able to see dozens or hundreds of them from your seats out there they do indeed Doppler shift back and forth but they shift by only about one one thousandth of one pixel on the digital camera image and you might ask yourself how in the world could you ever see these dark lines or the spectrum in general shift by one one thousandth of just one of the pixels on the digital camera and the answer is shown in the next movie here you zoom in on any one of these absorption lines like say that one and when you magnify it you can see that spectral line Doppler shift to the left and to the right and to the left and to the right and as it does so the amount of light hitting the neighboring pixels that you see shown here by the Pistons the amount of light changes in each of those neighboring pixels as it gets covered up by a dark spectral line and then revealed and covered up again and so the difficult challenge of measuring Doppler shifts and a thousandth of a pixel is met by simply measuring the amount of light in each neighboring pixel extremely precisely and that means you need a lot of light so that the fractional error in the amount of light in each pixel is very tiny so that's the game plan gather a lot of light spread it out into all of its wavelengths and measure this Doppler effect now let me show you some actual results this is one of our stars that we've been monitoring at Lick Observatory just 25 miles from here star 16 signe in the constellation Cygnus you can see it with your naked eye and I've shown a plot here of the Doppler shift measure a velocity of the star this reflex velocity in meters per second over the course of time to 94 96 98 mm up to 2006 he's seeing about 12 years let me show you back in 1994 the measurements that we obtained you can see three data points each dot represents a visit to the telescope we open the shutter we pointed at 16 signe and measured the Doppler effect you can see that these three data points are not in exact agreement but like any good scientist we are showing here the uncertainty in those measurements you might be able to see if you have very good eyes a vertical bar the error bar in those Doppler shift measurements which is our expected uncertainty in the measurement and you can see that this point here is high by a little more than an error bar or two giving us a hint that the star changed its velocity but you really wouldn't be sure from just those three measurements so we went back to the telescope the next year and here's what we got now you see some Doppler shift measurements that are higher than others giving you a suggestion that the star changed its velocity as if something were yanking on it but you still can't tell much and you are not even a hundred percent sure that you should trust this variation in the velocity so you should go back to the telescope again and take even more data and now let me just show you the next 10 years of Doppler shift measurements it's quite striking that the Doppler shift varied in a predictable way if you glance at this you might be able to see with your own eyes a periodicity in the data the velocity measurements go up and then down the star's velocity increased and then the star was jerked downward and over and over again the star repeatedly is being yanked around undoubtedly due to the gravitational pull of some unseen planet and you can tell just by your own eyes there in the what the orbital period of that planet must be from one peak to the next peak is about two years 2.2 years to be exact so we know that there's a planet orbiting this star every 2.2 years yanking the star around and there's another thing you learn right away from these data the amount by which the star has been jerked yanked around this amplitude the amount of velocity variation if you read over here on the graph 50 meters per second half of a football field length per second is how fast the star is moving and that velocity amplitude or wobble immediately tells you how massive the planet must be after all a very massive planet is going to pull gravitationally more strongly on its host star than a small planet will and so that velocity wobble can be interpreted using newton's laws of physics that every freshman learns here at Foothill College and determine I hope and determine the mass of the planet that's doing this yanking so in this case the inferred mass of the planet is 70% bigger than that of Jupiter so this is a big planet not too surprising you can see this star wobbling with your own eye so this is among the larger planets that we can find now there's one thing about this graph that should be really bugging you if it's not bugging you think harder so that you're bugged and and what should be bugging you is that the velocities the velocity of the star ramps upward taking almost two full years and then within about a week the star's velocity is jerked downward and then two more years go by or so and then the star's velocities jerked violently down again and this is not what you would expect if the planet resided in a circular orbit around the star where you would get a more smooth gentle variation in velocity instead this planet must be orbiting the star in an elliptical orbit bringing the planet so close to the star that it Yanks gravitationally strongly and then the planet swings out wide and then the planet comes in close again and so the idea here is that from this shape of the velocity variation you should be able to infer the shape of the orbit within which that planet resides and so you can actually deduce something about the size and shape of the orbit as well as the orbital period and the mass of the planet and here's what you would get by again applying newton's laws of physics here's the host star sixteen signe for reference there's our solar system with an inner four planets Mercury Venus Earth and Mars and then here's our new planet sixteen signe B that you see indeed is in an elliptical orbit it comes close to the star and when the planet is very close to the star it jerks violently by gravity on the star yanking the star's velocity down to a lower value so this is fantastic I mean I can't tell you how excited I am about the way this all worked out when we first started measuring Doppler shifts we had no idea that it would be so illuminating but now you can see you learn a lot about a planet its existence its mass its orbital distance the shape of the orbit and the orbital period all from these just simple Doppler shift measurements moreover the farther the planet is from the host star the cooler it will be in temperature a planet close to the star will be hot a planet very far from the star will receive very little of its host star light and hence it will be quite a cool pond so we can in fact estimate the temperature of a planet from data like these so it's a fantastic amount of information that I'll come back to about whether such planets might be habitable or not in this particular case I think the chances for habitability are quite low if I may be honest it's a giant planet bigger than Jupiter and our own Jupiter as you know is composed primarily of hydrogen and helium gases very little rocky components at all and it seems very hard to imagine single celled life and indeed multicellular life existing on such a gas planet like this one which is almost certainly also hydrogen and helium gas because any life forms would sink in the gases down to the hot dense interior and be crushed or melted to death so I think life on these kind of planets seems like a long shot but there are those who say it's not an impossibility maybe on a gaseous planet you could have life forms that float evolved to swim or fly like birds in the gaseous indeed dense gaseous atmosphere so we shouldn't rule out the possibility of life on gas giants entirely moreover as shown in this artist's rendering by Lynette Cooke giant planets may have giant moons and Lynette Cooke has added one such moon you see it shedding water because occasionally it comes so close to the star that it heats up losing its water to evaporation nonetheless it's possible that a massive enough moon could exist around a planet like this one so massive that it retains its liquid water and there could be lakes and oceans rendering this moon a suitable site for biology as we know it so there are extraordinary questions being opened up by the discovery of new types of planets and the prospects of moons that might be themselves habitable wouldn't it be amazing if it turned out that life in our universe predominantly lived on moons rather than on planets well I now want to show you my favorite star in the whole sky here's a map to help you find this starts its Upsilon andromedae there's a lot of stars here and the way you find Upsilon andromedae it's up tonight by the way very easy to find you you simply drive to the Andromeda galaxy turn left and there's the star you go a certain distance you can find it among all the other stars because it has this this arrow pointing right at it right and without that you have no chance here are the data it looks like a mess as part of the reason I love this star here's a graph again showing the measured Doppler shift derived velocity of the star over the course of time starting there 1987 let me repeat that 1987 all the way through 2006 the current time and you can see that the data points scatter all over the place you can't see any obvious periodicity here at all so we use a technique called a Fourier analysis some of you have heard of Fourier analysis we look for embedded invisible periodicity in the data instead of showing you a Fourier analysis right now and I will show you one in a minute another way of proceeding is to just zoom in on a little tiny piece of data like this little piece in here and if you look very carefully at that piece you see this now you're seeing only seventy days of data velocity measurements and if you look at those 70 days of velocity measurements the velocities went up and then down and then here's another piece where they went down and then up and then down and indeed all of the points can easily be fit on a very wave like so called sine wave of velocity variation indicating that there is indeed a planet orbiting this star the interesting thing though is the orbital period the distance from one peak to the next is only 4.6 days so this is a planet that whips around its star Upsilon andromedae taking only four point six days to go around once one year is four point six days for that planet amazingly close in obviously planet and striking because we never expected originally such close in planets to exist we now know of some twenty of them in fact the first planet found ever around another star by the Swiss team in Geneva found a four day planet around 51 pegasi so these planets are actually fairly common that are in in this case however that planet doesn't explain all of the data if you subtract the effect of this very close in planet around that star Upsilon andromedae what's left over in the original velocity measurements is shown here here in now are the velocity residuals what's left over again in meters per second over the course of time and you see that there is now still a velocity variation that takes about four years to wobble once and superimposed on that is yet another wobble a third wobble that takes about two thirds of a year every two thirds of a year the star wobbles due to some other planet that is to say there are a total of three planets orbiting this star that we've been able to detect a triplet of planets and here's the civil engineers sketch of the system you've got epsilon and dramedy you've got your inner planet your middle planet your outer planet of course we know their orbits the orbital shapes and the masses of those planets the outer one for Jupiter masses the middle one - Jupiter masses and the inner one a mere 60 percent of our Jupiter by the way I should stop here and mention something that's a little sad we don't have names for any of our planets we've never named them and we're looking for some naming scheme maybe somebody would like to have a planet named after them for example but we just don't have any names for any of our planets yet and and we're looking for some strategy or some technique by which some type of a you know poets or musicians or great scientists or something by which we can name the planets so it's it's kind of an interesting challenge how would you name the now 250 known planets around other stars I should say that I get letters in the postal mail however suggesting names for our planets and about a year ago I remember getting a letter from a 12 year old girl in Idaho and she said dear professor Marcy I'm a seventh grader in Idaho and I learned about your new planetary system in our textbook I don't know if you've named your planet so I'm still reading here she said but I have suggestions for you about how to name your planets around Upsilon andromedae okay so I keep reading and she says I think the outer planet should be named for Peter and she said I think the middle one I'm still reading should be named to Peter pretty and she said the inner one I think you should name that dinky and there's great suggestions I get like that from whole classes of kindergarteners who tell me what types of pizza the aliens like to eat on each of the planets it's always pepperoni every single time the other thing that's kind of I remember getting a letter about a couple years ago from a retired math professor and he sent me a postal mail also didn't use email I guess and it says dear professor Marcy I'm a retired math professor I've come up with a mathematical proof that there's no intelligent life on the inner planet in the Upsilon andromedae system kind of a mathematical proof how could this be so I keep reading he says what intelligence species would want to pay income taxes every 4.6 days mathematica fruit so here's what Lynette Cooke thinks the system looks like there's Upsilon andromedae there's a for Peter and two patern dinky and and then you Lynette cook with her artist's license grip extra hard in her hand has added something into this rendering for which we have frankly no evidence at all namely a ring around this planet of course it's a very logical addition on Lynette's part indeed all of the giant planets in our solar system not just Saturn have rings around them you may not have realized that so it's quite imaginable that moons comets etc get gravitationally ripped apart and turned into a smear of ring material around most of the giant planets in the universe quite logical so that would be quite a spectacular concept imagine someday we humans send spacecraft to other planetary systems and observe for the first time the ring systems the moons comets and asteroids around those planetary systems and how they differ from the same constructs in our own solar system well here is some data that we just released a couple of months ago and I wanted to share it with you this is a star in the constellation cancer star 55 you see again velocity over the course of time and now you're seeing data again going back to 19 well 88 some 20 years ago we started observing this star here at Lick Observatory just up the road and you see the data points now if you look with your Fourier analysis glasses on you can see a periodicity a very long period planet may be taking some 14 years to go around the star and if you've good eyes you can imagine these velocity measurements must also be going up and down so fast that you can't even see the up-and-down wobble of the star and so indeed we use a Fourier analysis and I wanted to share with you what we actually look at here is a Fourier analysis of those velocity measurements that I just showed you it's actually fairly to interpret these let me show you how you do it here are prospective orbital periods for planets we don't know whether they are or are not they're on the horizontal axis 10 days a hundred days a thousand days 10,000 days and then in the Fourier analysis we are able to compute the amount of power the probability if you will that such a periodicity exists in our velocity measurements and you can see sure enough here's a lot of power at 14 years yes you saw that with your naked eye a 14 year wobble of the star and now here lo and behold is evidence for a planet taking only fourteen point six days in this very tall spike of power that tells you that yes the up-and-down motion of that set of velocities was due to an inner planet taking two weeks to go around the star 55 Cancri so there are two planets orbiting that star we published this we were very happy and smug and we moved on the problem is that when you build a model on the computer and predict what the wobble of the star should be based on these two planets you get an answer that does not agree with our actual data points and so you can look at the velocities that are left over these residual velocities that I mentioned a minute ago and do a Fourier analysis of them and it turns out when you do that you find that the leftover velocities have power at a period of 44 days a third planet in this system okay fine we published that you and then build on the computer a model a computer model of three planets yanking on the star look at the velocities that are left over and do a Fourier analysis of them and lo and behold there is now power at two point eight days 2.79 five days to be exact a fourth planet in the system this one here is just a ringing effect of the periodicity that's actually here so there's in fact a fourth planet orbiting the star 55 Cancri now if you build a compute with all four planets yanking on the star and look at the velocities that are left over between what you observe and what you predict from the computer you see one last periodicity right here with a period of 260 days and in fact we were so shocked at this fifth apparent planet that we observed this star 55 Cancri both at Lick Observatory and in Hawaii at Keck at the Keck Observatory and we see this same fifth planet and all of the other four planets as well at both telescopes and at that point a couple months ago we felt confident to publish the paper Debra Fischer was the lead scientist on this so this is an exciting result we were rather surprised that it happened it's a system of five planets orbiting 55 Cancri the first quintuple planetary system ever found and here's what it looks like the 55 Cancri stars in the center there are four planets packed in fairly closed within about one earth-sun distance and then the fifth planet which is fairly massive about four times the mass of Jupiter out here and I thought you'd like to see how that planetary system compares to our own home solar system here's our Sun Mercury Venus Earth Mars Jupiter and Saturn out here and so what's remarkable is that both of these planetary systems have four inner planets indeed they're fairly small and the 55 Cancri system less than a Jupiter mass and then a gap and then after that gap one massive gas giant planet and who knows maybe 55 Cancri has yet more planets that we simply don't have enough data to infer yet so it's rather interesting that we're seeing what you might call kin of our solar system among planetary systems elsewhere in our Milky Way galaxy giving us a suggestion that indeed the laws of physics and chemistry have reproduced another planetary system that has some kinship with our own now here's what the system looks like in Lynette cooks from her paintbrush you see 55 Cancri an inner planet a second one a third one there's a fourth one that I can't it's right in here you can barely see it and then the fifth one here they are magnified star inner planet second three four and five five planets going around the star by the way one fun thing you can do don't do this at home though take take a hammer and smash all of these planets and smear out their material and you can smear them out into the original platter of gas and dust out of which the planets themselves originally formed the proto planetary disc out of which they formed and therefore we can reconstruct the original material around the young star 55 Cancri when those planets first formed so this is giving theoretical astrophysicists a lot of tools to understand the planet formation process now nasa loves this system too so I thought I would show you an animation of what NASA thinks this planetary system looks like so I'm gonna take you on a trip here here's the constellation cancer with 55 Cancri in here and now you're gonna take a flight through our solar system then out toward cancer and you'll see the 55 Cancri planetary system here's our solar system and here's 55 Cancri you'll see all five planets in succession notice that the planets have colors that one's blue that one's brown we have absolutely no idea what the colors of these planets are none whatsoever that didn't stop NASA one bit to be fair Neptune is bluish Uranus is somewhat bluish Jupiter and Saturn have a yellowy brown tint to them and we know why there are molecules in the atmospheres that give the planets their color when light scatters off of those molecules so it's not ridiculous that the planets would have these colors but frankly we we just don't know we to this day don't have any pictures of any of the planets that we've discovered so this is exciting we're seeing kindred planetary systems and this leads me to I think the most exciting topic that is really capturing my attention in my own research and that is how many earths are out there in our Milky Way galaxy I have to report to you with our current technology we cannot yet detect earth-like planets we can estimate how many there might be and here's how you would do it remember that our Milky Way galaxy contains 200 billion stars our survey has shown that about 10% of those stars have large planets like Jupiter and Saturn and Neptune that we can detect so if you multiply 10% of all the stars by 200 billion you very quickly realize that our Milky Way galaxy contains some 20 billion planetary systems at a minimum because of course we can only detect the Jupiter Saturn and Neptune's who knows how many smaller earth-like Mars like Venus like planets are out there perhaps more numerous and indeed I would suggest they probably are more numerous the small planets are than the larger planets so right away you can estimate that there are tens of billions of rocky earth-like planets out there among the stars just within our Milky Way that then leads to a very important and difficult quest among those tens of billions of Earth's how many of them are suitable for life at least life as we know it how many of the Earth's are habitable well that begs the question what do you mean by a habitable planet what are the properties the environmental conditions of a planet that render it habitable in the first place well we don't know too much but we're learning and it's the biologists not the astronomers who are telling us the answer and what the biologists have done is very clever they have ascertained the habitability of the earth our own earth by going to the least hospitable place on the planet Earth and among the least hospitable places on our planet is in fact the great National Park Yellowstone it's inhospitable because the water is coming out at boiling temperatures during the winter Yellowstone is covered by tens of feet of snow as it is right now and moreover the water comes out highly acidic so the biologists have gone to Yellowstone for about 20 years now studying how it is that life can survive in this hideous inhospitable environment and you might go yourself and take a look and see how life survives here's one example of a geyser spewing out boiling water coming off in this stream here and you'll see in most of the streams in Yellowstone different colors of the water well of course it's not the water that has different colors it turns out there are different species of critters microbes bacteria that live in the water and as the water comes off it cools off at different rates and so there are different temperatures streams in each of these curves and there's a different species of bacterium that thrives in that temperature domain and so you see dark green yellow bacteria red bacteria orange and brown bacteria these are bacteria with different pigments that only live in a little niche of temperature and so you can actually see the specificity of their environment within which they thrive and remember the water is coming out very hot you can bring a thermometer to Yellowstone and measure the water it's you know 150 degrees Fahrenheit 170 degrees Fahrenheit the bacteria thrive with no trouble and moreover the water as I said is highly acidic to prove this to yourself if you don't believe biologists go back to your high school chemistry teachers lab steal some of the I mean borrow some of the pH paper that you remember using in your high school chemistry class and take that pH paper and dunk it into the water there in Yellowstone and you can do that when you do so you find out even as an amateur biologist the pH is 2 on a scale of 1 to 14 so in fact the water is battery acid like in its acidity and yet there are bacteria like this beautiful angel hair like filamentous bacteria thriving as well as many hundreds of types of bacteria and algae thriving in this boiling acidic water that gets snowed on every winter in fact I got to tell you my most favorite place I brought a couple of slides of it in Yellowstone this is called churning cauldron you have to take a hike for about a half an hour to get to this place look at the water gurgling and gurgling up as it's boiling to the surface I wanted to measure the pH to check on my biologist friends of this thing churning cauldron but I didn't dare plunk my finger anywhere near that water lest I maybe pull out a stump so instead I tied the pH paper to a black metal clip and tied the black metal clip to a string and I tossed the pH paper into the water and here's what you pull out when you do that little exercise there's what was a black clip it's no longer black and the pH paper indeed shows to a battery acid like acidity and then as if to laugh in our human faces algae was drawn up on the string right here the green algae thriving wonderfully within that hideous boiling water there are dozens of species of back that also live in churning cauldron they are partying in there and indeed if he'll ever does freeze over I think there will be species of bacteria that will find that perfectly Pleasant as well so they're partying while we would shudder at the notion of such living conditions but the message these bacteria are sending us the message is extraordinarily profound for astronomy because these species are telling us that no matter the temperature what the acidity or alkalinity whether there's sunlight beaming down on them or whether they are in darkness they will still thrive there will be some species of bacteria through Darwinian evolution find that niche and thrive in that environment as long as there's liquid water wherever there's liquid water on the earth you'll find species that take advantage of it so there's no question I think in most biologists mind and I have to admit even in my own mind that in our Milky Way galaxy maybe within 10 or 20 light-years of us our planets that harbours bacteriological single-celled microbial life thriving in whatever conditions are on that planet as long as there's water and a very good reason to suspect because water is such a popular molecule in the universe that there's plenty of liquid water on many of the terrestrial planets elsewhere in our Milky Way so the only remaining question is whether or not Darwinian evolution normally and inexorably leads to intelligence is intelligent life a normal outcropping byproduct of evolution starting with simple life now this is a question we can't answer very well I'll walk you through the very simple argument that tells us that intelligent life ought to be common as well and here's the argument you know now that there are 20 billion planetary systems within our Milky Way many of them are quite old compared to our Sun remember our Sun is only 4.6 billion years old and our galaxy is about 10 billion years old so must be some Earth's out there that have been around for a billion or two longer years than our own earth has been around and so that leads to the question of all of those Earth's that are out there what fraction of them spawns intelligent life eventually well nobody knows the answer to this you can ask evolutionary biologists at Harvard University whether or not single celled life will normally evolve into critters with big brains and who are arrogant like us and you you they can't tell you the answer um the least optimistic answer I've ever heard is that intelligent life is a one in a million throw of the dice okay if it's one in a million you can do the math one in a million out of 20 billion tells you immediately that our Milky Way galaxy must contain thousands indeed probably tens of thousands of civilizations and indeed many of them advanced by millions or maybe even billions of years beyond the technology of our own civilization so we would expect thousands of these great civilizations out there just within our Milky Way galaxy alone this result is I think no surprise to any of us it's certainly no surprise to the science fiction writers and the science fiction film makers who've been telling us for decades that the Romulans and the Klingons are so numerous out there that they need stoplights to avoid running into each other and you know you got to go out go out there with some caution less maybe they're hungry so that's the premise that we've all grown up with as children the problem though is a profound one if our galaxy is in fact teeming with thousands of advanced civilizations with their great probes that scatter and investigate our whole galaxy where are they why hasn't any of them apparently come here left a camera on the moon an obelisk some seismometer some sort of a instrument that we would recognize as technology there are to be sure footsteps on the moon but there are hours no one else's that's puzzling without any erosion on the moon we are the only footsteps there similarly we've photographed Mars to quite fine detail no scientific instruments no obelisks no sign that any advanced species came left some trace of its existence and I think the greatest galactic flytrap that we know of is the earth clearly an advanced civilization many light-years away would have taken a picture of the earth seeing that it's a shangri-la with palm trees beachfront property set up a golf course here or a resort hotel this could be a great vacation destination for the folks at Tau Ceti but they didn't they never came here it's true that the humans you know we humans might represent such a precious commodity that maybe they're protecting us but we've only been here on the earth for a blink of an eye the last 2 million years in all of the 4 billion year history of our earth no other advanced species came and set up a resort hotel on the earth nor left any trace that they ever came here none that we all agree on scientifically anyway came here UFOs aside so it's very puzzling that a galaxy teeming with intelligent life has left essentially no trace the Romulans and the Klingons and even the Galactic Federation according to Star Trek power their spaceships with matter antimatter engines where's the gamma ray exhaust that we would see with our gamma-ray telescopes we don't see them the night sky shows no great spaceships criss-crossing our solar system we don't see even robotic probes sort of orbiting Mars or orbiting the earth watching what we do century after century it's a little puzzling that a galaxy so teeming with life has hidden itself this apparently so successfully and as Jill tarter will discuss in the upcoming Foothill lecture series the SETI searchers the search for extraterrestrial intelligence scientists have looked very hard for four years and let's all hope they continue looking for another century but so far not detected any radio or television transmissions picking up their spillover military or telecom communications from one civilization to the next one spacecraft to the next we haven't picked up any of that transmission so there's a growing list of what you might call non detection z' of the advanced civilizations that we imagine we could have detected were they actually there so we need to be honest we need to suggest that perhaps Gene Roddenberry didn't quite have it right maybe the number of advanced civilizations is not as great or maybe indeed space travel is not as easy as is depicted in science fiction and it's still puzzling despite all of that as a possibility that they've been overly optimistic because of course we humans have already sent small robotic probes that have left our solar system pioneer Voyager they're leaving and they're going to go out for tens of thousands of years and if we humans continue to send out a probe every couple of years that leaves our solar system we ourselves will be populating let's say our galaxy with probes if the galaxy is filled with advanced civilizations why aren't some of them at least doing the same thing they could have and we would see their effects so it's puzzling that the Galactic ants have not come to our kitchen yet now one possibility for the absence or the apparent absence of advanced civilizations is that if you indeed expect thousands of them to have existed in our Milky Way galaxy during the past let's say five billion years then of course in order for one civilization to overlap in time the next civil and the next civilization they have to last long enough for one civilization to overlap the next one and if you do the math a thousand civilizations spread out over five billion years means that civilizations better darn well last a few million years in order for one of them to overlap the next one that comes along and that begs the question how long does a civilization last that has high technology the ability to build radio telescopes spacecraft and of course weapons so we don't know whether or not in fact our galaxy had been populated with civilizations long gone and that we just are not lucky enough to be overlapping one at the present time perhaps our galaxy is like some sort of galactic Christmas tree where the lights flicker on flicker off another light flickers on flickers off and it's rare for two or three of the Christmas lights to be on simultaneously at any given time so that may serve as some kind of a challenge for Humanity we have a very serious challenge to somehow last long enough to overlap and therefore be able to communicate with our galactic brethren with that rather depressing note there is an optimistic point of view and the optimistic point of view is that life is probably common in our galaxy and elsewhere in the universe at least simple life because the petri dishes exist in the billions the building blocks of life are abundant we certainly know that water exists in comets in between the stars in galactic clouds and water exists on many different planets even within our solar system often in the form of ice and sometimes liquid water so there's no question that the elements that life depends on are abundant the power exists in the Stars geothermal energy of course tidal energy so I think there's no question that life is a common property of other planets other moons at least primitive life maybe cockroaches and so on are common but what we don't know is whether or not habitable planets spawn intelligent life so we're beginning to look now seriously for truly earth-like habitable planets and the best way we're going to find habitable planets is with a NASA mission that is being built about five miles from right here at NASA Ames Research Center the Kepler mission will launch in one year February 2009 what that mission will do is look at nearby stars to see if they dim as the planets orbit in front of those stars blocking some of the Starlight what a clever idea just watch the stars and see if they dim when an Earth crosses in front and this Kepler telescope will have a digital camera in the back watching to measure the brightness --is of stars to look for earth-like planets we hope to find somewhere between 200 and 400 earth-like planets with the Kepler mission the first Earth's ever found that will be very exciting in addition at Lick Observatory on the top of Mount Hamilton we're building a new telescope dedicated to finding earth-like planets here's what it looks like right now with snow on the ground at Mount Hamilton have you been up there this winter here's another close-up view of our new telescope this will measure the Doppler shifts of nearby stars so precisely and so frequently that we'll be able to detect earth-like planets orbiting the stars yanking gravitationally on them here's a simulation of what our data should look like velocity over the course of one summer here in the San Jose area and we'll see the stars wobble here's the Fourier power spectrum we'll see the Stars wobble as a planet of a few Earth masses Yanks on that host star so with both the Kepler mission and this telescope on Mount Hamilton we're pulling out all the stops to find out if other Earth's are common in our galaxy and what their temperatures are their orbits whether they have any similarity to our own earth that begs the most exciting question of all if you find an earth what do you do well it's pretty obvious what you should do get all of your friends who have radio telescopes and radio dishes and point them at that earth and try to pick up the summer reruns of I Love Lucy coming from that planet thereby telling you that there's no intelligent life there at all but maybe there will be something more intelligent than that and in fact the SETI Institute located right here a few miles away in partnership with UC Berkeley is building a vast array of radio telescopes funded by Paul Allen of Microsoft funding the construction of dozens and hopefully hundreds of these radio dishes with one primary purpose point them at a nearby earth-like planet and try to pick up radio or television transmissions from any civilization that might be there it's very I think tear-jerking ly compelling to imagine that within our lifetimes we may learn of other advanced civilizations that are out there wondering whether there's any civilization here on the earth and I'm sure that Jill tarter will describe their efforts to use this radio telescope at that next lecture that she's giving and we can only hope that by exploring the issues of biology along with astronomy maybe within our lifetimes we'll learn some of these answers so I'll stop there thanks knights dr. Marcia now dr. Marci has indeed agreed to answer questions we do ask you to ask questions and not make speeches and there are microphones in the middle of the hall where we ask you to line up and then I'm gonna ask dr. Marci to recognize them fairly in turn one and the other and we'll continue for a while with formal questions so thank you so much for an alumina talk we were delighted to hear all the latest news including Jupiter and for Peter and now I thank you over to the audience yes has the Fourier analysis has that been done in detail for our solar system have you detected evidence of the shift from other planets after you take out the effect of Jupiter yes all have to be accounted for in our measurements because just as he suggests Jupiter and the other planets yank on our Sun and indeed yank on the earth so when we make Doppler measurements of other stars we have to first subtract away the effect of all the motion of our own earth some of which is caused by the pole from the other planets before we the Jet Propulsion Laboratory by the way is the source of that information for both the Kepler mission and the Doppler shift what effect does the plane of the orbit of the planet have an effect on on your measurements toward us it's the orbital plane is tilted 20 degrees or 40 degrees or 60 or even worse 90 degrees Faith's on an orbit then the star and the planet wobble in a plane that is up and down or left both and we don't see any approach or recession of the star at all and so we would miss the detection of any such planets it's exactly right in the case of the Kepler mission it's even worse because in their case for Kepler the planet has to be in a plane exactly lined up or nearly exactly lined up with the our earth so that the planet actually sits right in front of the star if the orbital plane is tipped just a little bit the planet won't block the Starlight so you indeed the Kepler mission will be studying 100,000 stars with the full knowledge that only about one in a hundred of the planetary systems will be adequately seen I have been to your lecture a couple of times before and the new telescope at Mount Hamilton is the new element you said before that with your Doppler shift method you can't really get down to the earth-like planets so has your algorithm been improved and also how can you build something better than Keck for one thing our technology is the Doppler shift of a star the speed of the star to plus or minus one meter per second so I can tell you whether a star is moving this fast it's rather amazing a star 100 light-years away we can tell you whether it's strolling toward us or away from us so that's one thing the real advantage of this dedicated telescope at Lick Observatory is that we own it ourselves the University of California owns it we will observe stars every single night a single star will observe it every night we'll have a host of 50 stars observe them every night and the advantages is really wonderful if there's an earth-like planet in a closed in orbit taking say 30 days to go around the star you need to watch that star every day every night I should say for 30 straight nights and preferably 60 or 90 nights we only get a few nights on the Keck telescope so as large as the Keck is we have to share it with so many other people that we can't watch with high enough cadence to detect clothes in Earth's and that's the advantage yeah dr. Marcy you indicated about a tenth of the stars that you observed might have large planets that you can detect I wonder to better understand on a given night say at Lick Observatory if you if observing time wasn't a question how many stars are above your intensity threshold and basically how many planets like do you think you could detect on from the from that sky and how does that compare to like would there be a thousand visible stars to the naked eye yeah you actually you hit the nail on the head at the Keck telescope we can observe stars as faint as 8th magnitude for those of you who know the magnitude system and there are several thousand stars brighter than a the two that are normal hydrogen burning stars amenable to the Doppler measurements so we wish we were monitoring all of the several thousand stars that are bright enough as you say to to allow these Doppler measurements to occur moreover we wish we could make the Doppler measurements once a week twice a week or at least two or three times a month in fact we don't get telescope time that often which is part of the reason we're trying to build this new one so typically the bad news is most of the stars and we are monitoring 2,000 of them most of them we are able to observe only twice a year so any planets that take a few months to go around the star we will miss most of them because the planet goes around around and we've been gone and then we come back to the telescope and get a snapshot of the Doppler shift so you know your your bottom line answer is we are starved for let's go resources to find The Neptunes and indeed the Earth's that we otherwise could find if we had more telescopes at our disposal and in the end its funding if we had more funding we could build more telescopes like this new one at Lick Observatory that finally will give us a chance to find Earth's thanks very much it's been theorized that life on Earth was possible because we have gas giants in our solar system right that block off intense bombardment over a long period of time the fact that you have found gas giants and other solar systems would encourage the fact that there may be habitable planets because of that would you expand on that yeah it's a brilliant comment and just to fill in the some of the details we now believe that when our solar system first formed there were thousands of times more comets and asteroids than there are today but in the intervening four and a half billion years Jupiter the big gravitational bully in our solar system slingshot out by its gravity most of the asteroids and comets or indeed maybe sucked those asteroids and comets into Jupiter flung them into the Sun there by cleansing the solar system of that early solar system debris if that were not the case if Jupiter didn't exist we would be bombarded by comets and asteroids every few months as was the case in the early part of early era of the solar system and indeed most of you know that the dinosaurs were probably wiped out by a giant impact some 60 million years ago or so so indeed it's probably true that we owe our existence and indeed most of the mammalians on the planet Earth at least the larger ones Oh their existence to the presence of Jupiter so as you say the fact that we found a fair number of Jupiter's out there gives us hope that similar cosmic vacuum cleaners are out there to do their job yeah yeah I wanted to follow up on your question about the off-axis orbits and are there ways you can even that are the pictures we see in the common crest think the one she showed up here say always a for mass Jupiter but that's really sort of that if there's no way to tell us off access the minimum mass and all these pictures of what the layout looks like and similar it is seems to me I got taking a lot of a leap of faith I'm saying that it's an access view if it's off max that's all they'd be much larger much larger and changing or are there signals there that tell you that it is on axis versus being various tempted so you're overly pessimistic but you're on the right track so let me let me try to give you my sense of it all you're absolutely right that because we don't know the tilt of the orbit we actually only learn the a lower limit to the mass of the planet if the planets orbit orbital plane is tipped 30 degrees the planet's mass will be a little bit bigger 20 say percent bigger than what I was quoting and in fact the average tilt about 45 degrees tells you that the masses of the planets we've found on average are about 30% more massive than that minimum mass just from statistics of the various orientations of the orbital planes that's not too bad you're welcome to multiply all of the mass as I mentioned increment them by 30% and instead of 1.8 Jupiter masses they're 2.3 Jupiter masses or something so that's not a big problem the other thing that you mentioned though is is too pessimistic the actual sizes of the orbits and the shapes of the orbits those we learn unambiguously independent of the tilt of the plane so in brief that information and indeed the temperature of the planet owing to its distance from the star we learn unambiguously as well so everything except the mass is nailed down and even the mass even if it's off by 20 or 30 percent it doesn't matter that much yeah I have a comment on where the aliens are I was I was mission scientist on Apollo 14 and the command module pilots do Russa and I tried very hard to get the landing site moved from from arrow to a limb of the moon near the near of the limb and the reason was that we'd asked ourselves where would the aliens leave the obelisk I hardly obvious answer was in the middle of orientale the great bullseye which is just around the corner he'd never see it from the earth we wouldn't know it was there until we got Space Flight but if once you see it it covers most of the disk of the moon but unfortunately the landing the lighting conditions require that the Apollo landing sites met that it was always in the dark during every Apollo mission and force 2 and I were trying to get them to shift it so that that re intolerably lit up and he could take some photographs of the center of the place we we didn't get it done we were too embarrassed to tell them what we're real reason was and the the result wise on your part the result of that is that we still don't have pictures of the center of our entire and anything like the resolution that he could have taken so we don't know that's fascinating I I'm very appreciative of your comment and I think if I may just expound on this we certainly do want the most detailed pictures of the moon down to a resolution of a few inches in case the seismometer is left by the aliens you know our pocket-sized and similarly for Mars which I consider a little more compelling we don't have very high resolution images of the entire surface of Mars at the sort of one foot or one inch level so there's a real reason to have Rovers on Mars two pictures of Mars to look for any evidence of some past civilization that came you know and left their picnic basket there yes what's the maximal tilt that you could that your methods would work to detect planets sorry what's the tilt of the electic oh how can we determine the tilt of the orbital plane no what's your if it's if it we're faced on then we can't see any yeah I just wonder how far could it be where you can still detect things we're using your methods well the wonderful thing about this Isis pyramid yeah well the wonderful thing about the Doppler shift method is that no matter how far away the star is if you can measure the Doppler shift repeatedly you can determine whether there are planets so the real restriction is brightness stars that are too faint don't give us enough light enough photons to fill up the pixels with enough light as you saw in that animation to measure the Doppler shift very precisely so stars that are fainter than tenth magnitude with the Keck telescope we labor we struggle we take fifteen or twenty minutes time is ticking by we could be doing other stars fainter stars still we don't bother with them because they're so expensive of telescope time that it costs us too much time to observe that faint star so the answer to your question is we could do tens of thousands even hundreds of thousands of stars in our galaxy and watch for planets if we had enough telescope time to do them but in the end we restrict ourselves to the brightest and hence the closest of the stars so the brightness is the limitation the brightness but we're bright enough even for eighty percent that's right exactly okay thanks yeah I have two questions one is do you pre select stars so that you use very stable stars because a lot of stars pulsate and they will have periods just due to the atmosphere move movement that's my first question oh I'll answer it yes we avoid pulsating stars our Lyra Cepheid variables even giant stars so-called red giants have surface motions undulation z' that mimic Doppler shifts with some kind of periodicities in them so we avoid all of those stars and that's why you heard me say parenthetically we concentrate our study of just stars that are nearly sun-like somewhat more massive than the Sun somewhat less massive but normal hydrogen burning quiescent stars that are indeed not undulating as you say yeah makes sense and the second question is in order to get the Doppler shift such small shifts in wavelength a thousandth of a pixel right whenever you take a spectra you need a reference source you have to have an extremely stable reference so in order to measures what do you use yeah iodine iodine whole part of the story it's a great question we actually insert into our telescopes Lick Keck anglo-australian telescope a glass bottle filled with iodine gas at a fixed temperature 50 degrees Celsius and we forced the Starlight to pass through that iodine gas and the Starlight that emerges has spectral lines in it not just from the star but also from the iodine those iodine lines do not participate in the Doppler effect and so we use them as the reference lines of known wavelength as just exactly as you said against which to measure the Doppler shift of these stellar spectral lines thanks yeah I noticed in one of your slides that was indicating the Fourier spectrum of the planets right that there seemed to be a pretty strong set of side lobes on one of the planetary peaks that's right I was wondering what is that indicative of it could that be some second-order of you know fact you know what it is it's a stroboscopic effect that we're all familiar with if you've ever watched hubcaps of a car driving along with florescent bulbs you sometimes see that the wheels almost seem to be going backwards what happens is we measure the Doppler shift every night night after night after night the stroboscope is the nightly cadence of our measurements analogous to the flickering of fluorescent lights that strobe on and off and so if the planet has an orbital period of let's say 3.4 days and we only observe it every night we actually see the orbital phase of the planet the actual position of the planet when we make our measurements at certain instants of time and it might almost appear that the orbital period is a little different than we think it is or in other words other apparent periodicity z' can emerge from the data that are artificial and due entirely to this stroboscopic effect of our forced nightly observations and so that the other peaks that you saw there as you called them correctly side lobes are due to our nightly observations and also monthly observations we tend to observe you know at the same phase of the moon frankly near new moon because our stars are bright enough to handle it so we have a nightly cadence and a monthly cadence and a yearly cadence because the stars go behind the Sun for half of the year and because of those those stroboscopic effects we get some of those outlier peaks that we can dismiss by modeling them I see I just okay only those that are now standing I'm told yes okay so let's assume that I am a member of an observatory on a star in the Pegasus system okay and I'm looking back at our solar system this way right here and I detect our Jupiter right as a as a large planet and I'm also fortunate to be able to detect Venus Earth and Mars I cannot tell if there's life on any of those and right back to you know two out of three don't have life that's right so we didn't find out that there was no life on Jupiter absolutely on Venus and Mars until recently right in my own lifetime right so to be able to determine that there's a habitable planet that has life it seems to be very remote yes let me let me comment though to give you some hope there there - two things we have to do one I mentioned point radio telescopes and look directly for advanced life but Morris I think stepwise is to build a space born telescope and indeed NASA wants to build it it's called the terrestrial planet finder a space born telescope like the Hubble but it would probably have several telescopes all attached working in tandem an interferometer to take pictures of those earth-like planets notice we have no pictures of any of our planets if you can take a picture of a planet you can use the light analyze it with a spectrograph a spectrometer and look to see if there are signatures of biology on that planet chlorophyll for example has a distinct spectral signature you might look for methane given off by the by cows flatulence and so on on that planet so there are ways that you might spectroscopically analyze the chemistry of another planet and at least make a reasonable guess as to whether there's life and what type of life might be there so that's the real future in the 10 or 20 year time frame a space for in telescope that takes pictures of and spectra of earth-like planets yeah 55 Cancri planets have names okay this a very good question the five planets around 55 Cancri have no names at all isn't that sad I think you should try to come up with some names and send me a letter and then in my next lecture I'll tell the audience what names you gave those five planets okay all right that's good yes good question is there beneath any planets discovered around binary or trainer ESA's yes there are about twenty planets now known around binary stars one of them I even showed 16 signe B has a stellar companion it was even shown in Lynette Kooks rendering sixteen signe a and it's a system where the two stars are so far apart that in fact the planets can orbit one or the other star and the two stars don't gravitationally perturb the planets oddly by the way sixteen signe B has the Jupiter that I showed in that sawtooth velocity curve sixteen signe a has no planet at all that we can detect no Jupiter's anyway so it's kind of odd the two stars formed at the same time out of the same material one has a planet the other one doesn't yes I've been have I've been having a hard time imagining gas giant planets inside the orbit of mercury lasting four to four billion years do we know that their gas giants could they be rocky cores metallic cores any ideas you know what we are absolutely positive that they are gas giants and you might find that surprising to be so sure but the reason is a few of these close in giant planets have a mass about that of Jupiter by luck some of them indeed cross in front of the star blocking some of the Starlight and the amount of light that's blocked tells you the diameter of that planet we already get the mass of the planet from this Doppler effect and the wobble of the star knowing the mass and the diameter of the planet allows us to determine the density and it turns out that most of these giant planets have densities very similar to that of our own Jupiter about one gram per cubic centimeter about that of water it's actually gas under high compression so there's almost no doubt I mean literally no doubt that these are planets composed of hydrogen and helium with self-gravity compressing them down to densities very much the same as our own Jupiter and Saturn yeah amazing yeah well related to that question what keeps the gas yeah well they left planet just the gravity alone yeah I mean that was the other implied part of his question and thank you for reminding me of it you might worry as I think you were worried that a close-in giant planet would be so close to the star that it would be the planet would be blow-torched by the star to a very high temperature that's true and that it's such a high temperature the molecules would be racing around due to that high temperature so fast that some of the molecules would achieve escape velocity and leave the planet allowing the planet to slowly but surely evaporate away and the terms that you can do that calculation that's second semester physics in most colleges and you can actually determine how fast the molecules are going at their equilibrium temperature and what the escape velocity of the planet is turns out the hydrogen and the helium does not achieve escape velocity the vast majority of it will just stay gravitationally bound to the planet and so the planet actually remains intact for billions of years despite its high temperature and it's gaseous nature yeah you said there was a we saw a slide of an elliptical orbit of a planet and you said that you didn't believe that there would be life on right but so how common are spherical orbits and you you also said that the laws of our biology that we have on earth might not apply doesn't that mean that there could be life yeah litical yeah it's it's a really creative question and I have to I didn't mention this the vast majority 85 or 90 percent of the planets we have discovered of the 250 found by us and the Swiss team 85 or 90 percent of them reside in these elliptical elongated orbits not circular orbits as we find in our own solar system so that's a a little frightening and puzzling and as you suggest it suggests that the temperature of the planet will very hot cold hot cold as the planet gets close to and then far from the star and when there are such wide temperature swings you might imagine that biology would have a difficult time surviving the water freezing and then boiling and then freezing again and so on so that that is an issue with regard to the laws of biology being perhaps different elsewhere I can only say you may well be right we have a long history we humans do of thinking that our little niche in the universe is the way the whole rest of the universe is you know the folks in Kansas for a long time thought everybody was white and Christian but it turns out that elsewhere not everybody is white and Christian so we may be similarly arrogant right now in thinking that biology elsewhere is even remotely like biology is here on the earth and so we have to be very conscious of our own arrogance and self-centeredness and throttle centrism you might say biocentrism that maybe life elsewhere is more like the Horta in Star Trek based on silicon and so on so that's that's a that should give us a little pause for thought and a little humility last question the you were looking looks like you're looking primarily at visible light would it be that wavelengths way above or below might give you more why are you looking at visible light and what is it about other wavelengths yeah that's a good question the first answer is stars like our Sun emit most of their light at visible wavelengths blue green yellow and red but there are other stars the cooler stars indeed the small stars in the galaxy the M Dwarfs emit most of their light in the infrared and there are several groups in the world very rapidly designing and building spectrometers for the backs of their telescopes that will take spectra of stars in the infrared for exactly the reason you said so that then they can measure the Doppler shifts of these cooler stars that emit most of their light in the infrared and we have a hard time observing those little stars in the visible light that we use because those little stars emits so little of that visible light so if you want to know who is on these other planets come back April 23rd for Jill tarter please everyone drive carefully we'll see you next time

Channel: SVAstronomyLectures

Views: 36,164

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Keywords: Astronomy, science, space, exoplanets, extra-solar planets, planetary science, other Earths, Doppler shift, astrophysics, telescopes, SETI, alien life, life out there, earth-like planets, hot Jupiters, jovian planets, Geoff Marcy, Extrasolar Planet (Celestial Object Category)

Id: -7ChJUyoKDA

Length: 92min 28sec (5548 seconds)

Published: Sat Oct 05 2013

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March 5, 2008 Dr. Geoff Marcy (University of California, Berkeley) Astronomers have discovered hundreds of planets orbiting other stars. In this talk, the scientist who discovered more planets than anyone else in the history of the world discusses what kinds of planets we have found so far, and what a new generation of telescopes might find in the future. Could discoveries of planets that resemble the Earth spark a new era when we could someday begin communication with alien life? Dr. Marcy and his co-workers pioneered a key technique for finding planets around other stars. Category