The Mysterious Star HD 139139 with Dr. Andrew Vanderburg

last week it was announced that a star HD 139 139 was found to be behaving very strangely in the Kepler 2 data it was as though 28 planets all but one about 1.5 times the size of Earth passed in front of the star but at random they did not appear to be periodic as you would expect with orbiting planets today I'm joined by dr. Andrew Vanderburgh one of the scientists trying to unravel the mystery of the star welcome to event horizon with John Michael Gaudi a [Music] in today's episode John is joined by dr. Andrew Vanderburgh he received his PhD in astronomy at Harvard University in 2017 and was a postdoctoral associate at the harvard-smithsonian Center for Astrophysics until he started his Sagan fellowship at the University of Texas in Austin his research focuses on extrasolar planet detection in particular studying the Kepler space telescope data welcome everyone to event horizon with me John Michael Gautier if you enjoy what you hear fall into the event horizon hit the like button and become an active subscriber by ringing the bell dr. van der Berg welcome to the program thanks for having me now doctor you have discovered in the Kepler two data a very very strangely behaving star can you give us an overview of the star that's right we've discovered a star that is called HD 139 139 that we call the random transit er which appears to have dips and it's brightness like the ones you would expect for planets that cross in front of their star but the weird thing is that none of them seem to line up and none of them seem to correspond to multiple orbits of the same planet these dips look like planets right yeah they look just like the dips that you would expect for planets to create they just don't seem to come at the right times which suggests that whatever this is it isn't periodic right right or it's either so complex ly periodic that we haven't figured it out yet now that would require a whole lot of planets though wouldn't it because you only observed with the Kepler team mission for what eighty-seven days yeah that's right we observed for 87 days and we detected 28 dips and as far as we can tell none of them were at most a handful seemed to line up with one another so that would require something like 14 or 15 planets if we were to imagine that all of those were caused by planets do you have any data on how distant they could be from the star if they are periodic I mean could they be very far out and just slowly passing in front of the stars they orbit very slowly or do you have anything any indicator that they might be closer to the star yeah so we have a few pieces of information about each of the dips one of them is the depth of the dip or how much light is blocked that roughly tells us the size of whatever object must be causing this demean and brightness we also have the duration of the dip or how long the dip lasts and this is what gives you some information about how far away it might be from the star because the dip gives you roughly the speed at which the planet is orbiting the star now there are a few factors that can affect this but generally we see dips that last from a little bit less than our up to eight hours and those tend to be corresponding the planets in orbits fairly similar to the ones we see around other stars with planets detected by k2 they don't appear to be really really distant if they are a little bit further out than usual now the star itself this is a type G star so somewhat sun-like how close is this to the Sun it's pretty close we can measure the temperature using our spectra that we took from observatories like Fred Whipple Observatory and McDonald Observatory and we measured that the temperature of the primary star this is a pair of binary stars is about 50 to 80 or 50 to 20 depending on how you measure it plus or minus about 50 to 100 Kelvin and that puts it right around where we know that the sun's temperature is which is about five seven seven and seven Kelvin can you tell if these objects are orbiting that main star or the secondary star in the system no we can't tell they're so close together that in the Kepler data they all fall within the same pixel so it's very difficult to distinguish which star is the source of the transits to make matters worse in this data set Kepler is moving back and forth over time which makes it even more difficult to figure out which planet which star is causing the transits that we see so could that be a solution that maybe you have some sort of bizarre situation where you have some planets orbiting one star some planets orbiting another and maybe that could be causing the non periodic appearance of the star system it's possible but it's still pretty tough to make that work for one thing if you had some planets orbiting one star and some orbiting the other star you still might expect to see periodicities there could be bunches of planets orbiting each of the stars but that situation starts to strain credibility a little bit and the reason is that if all of the planets are some of the transits were on the fainter star the planets which caused those transits would have to be bigger to cause that same amount of total light loss to take place in the system so if they were around the smaller star they would have to be roughly Jupiter sized and if some of them were around the bigger star they would have to be about the size 1.5 to 2 times the size of Earth so that's a lot of coincidences because you now have to have large planets on one star small plants on the other star that all added together when you add together all of the flux from the system give you transits of about the same job so that feels a little bit difficult to make work it's a little bit contrived now that's one of the one of the interesting points of the stars that all the dips appear to be about roughly the same size so if these are planets there except for one they're all roughly the same size right what could explain that is is there some other explanation like for example say you have a disintegrating planet or something like that could that throw out dust in such a way as to appear that way it's possible so we only know of a handful of disintegrating planets three disintegrating planets around main sequence stars and one around a white door and one of the characteristics that's common to all of these objects is that the depths of their dips change quite a bit they can go from zero depth basically no transits at all to their full depth over the course of just a few orbits and that's one of the reasons why this is a potentially attractive way to explain why there are no periodicity maybe most of the time those dips are just gone you don't see anything coming out and then occasionally there's a poof of dust which causes a transit that then goes away very quickly by the time the integrate and object comes back around for its next orbit and you just lose your periodicity that way the problem though is that you might expect to see dips in between the full depth which roughly would be about 200 parts per million in this case and zero it's maybe possible that there are some of those that we miss just because once you get to a much smaller than about 200 parts per million you're hitting the noise floor of the Kepler data it's just too noisy detects things that are much shallower than that but it's still a little bit hard to imagine based on what we know about disintegrating planets today how can you rule out dust in this case what observations can you make for example can you look at light and see if it absorbs blue light and red light differently and try to determine if this is dust or if it's solid planets is that the next step in observation of the star yeah that's potentially another stuff we could take although there may be some wrenches thrown into that as well if you imagine that dust is causing these dips then potentially yes if the dust particles are small then you would see that the transits should be deeper in the blue light than they are in red light and that's what we've seen for objects like voyage on star but when we've tried to do this for disintegrating planets we haven't necessarily seen this and we've come to the conclusion that maybe the reason that we don't see it is because there are no small dust particles because they were so small that they sublimated a wave thanks to the intense radiation environment so this is a disintegrating planet very close into its star that's very hot that we may not see that color dependence of the dips like we would or something further out like we imagine is going on around poiish on star so would that be like basically big rocks coming off of the planet and any small stuff just gets disintegrated and blown out but you still have chunks essentially of the disintegrating planet yeah it doesn't actually have to be that big of a rock anything larger than a few microns would be very difficult for us to detect of wavelength dependence for roughly the size of your particle is the wavelength at which that dependence starts to turn on so if you have particles that are even maybe 10 microns we just don't have observational resources to make those observations well and see that there is a difference in the depth below the size of that dust particle and above the size of that dust particle now in reading about this start and reading your paper one thing struck me is that there seems to be some sort of fundamental issue with every explanation anybody's thought up so far except one which might be the idea that this star has sunspots on it that are very short-lived tell us about that option yeah so that would be a new thing we know that there are sunspots on our Sun that appear and they live or a few months a few times the Sun orbits appear oh tation periods and then they decay away and we see star spots on this star and the light curve or we infer that they're there based on the light curve because they behave similarly we see this slow modulation of the brightness of the star which is characteristic star spots that lasts a long time so you see these large dip so they're roughly the same depth as the short transit light dips that we're seeing this is pretty common we see this in thousands and thousands of stars in Kepler where we have long-lived spots what would be unusual is if the spots were to appear very quickly over the course of maybe 30 minutes to an hour last for anywhere between 30 minutes to eight hours and then disappear just as quickly that would potentially explain these transits now it's not like anything we've seen on the Sun and it's not like anything we've seen in the other kepler stars so we have that problem to contend with but as far as we know there's no reason why it couldn't be the main reason we include an explanation like that is just because we as you said notice that all of the other explanations we could think of had some flaws and this one doesn't there's really no reason we can think of why this can't be the case but there's also no good reason for us to think that it is the case so it's a little bit out there it's maybe a little bit of a shot in the dark but maybe it'll turn out to be correct well it's kind of interesting because since the star is so sun-like and it's younger than the Sun as I recall it's only one point billion years roughly that might yield clues on the earlier history of the Sun maybe the Sun did produce sunspots like this and it somehow as a aged stop doing so yeah it's possible you would expect if this was something that all stars did that we would have seen more examples of this though before so it seems likely that this is at the very least kind of an unusual star and maybe this is an unusual process if it is something intrinsic to the star now uniqueness is always noteworthy within astronomy because if you only see one example of something then it seems a little weird out of you know hundreds of billions of possibilities you only see one but is there anything close to the star that's been noted before other than of course Boyajian star not to my knowledge we've seen a lot of weird transits as you notice as you noted Voyager on star we've seen the differ stars around young stars which showed very similar dips to the one around volition on star but we know that there must be dust in the system from the protoplanetary discs we've seen transits that only happened once or twice that could be caused by planets we've seen some that have happened only once or twice or happened a periodically that are shaped funny that make us look like comets the weird thing about this system is that the transits are otherwise very planet light they're symmetric they're about the right depth or some of the most common planets in our galaxy super Earths they're about the right duration for planets on relatively short period orbits like the ones that we expect to see transiting it's one of these cases where if you didn't look at anything but the periods if you just looked at that light curve by eye you would say oh yeah that's a multi-planet system and only on closer inspection do you see how weird it appears to be the test spacecraft yeah which I know 10 is going to be looking close in but some people say it's gonna be taking data that might be useful for objects further away which for reference this object is what about 350 light years something like that yeah are you gonna be able to use tests to study this not anytime soon so right now Tess is conducting its primary mission where it observes most of the northern sky most of the southern sky it's already finished most of the southern sky and it's about to flip to the northern sky right around now I guess and it's actually leaving out a part of the sky right around where the star sits and that's because test is a satellite not a spacecraft orbiting the Sun like Kepler and Tess has to contend with the earth and the moon and it can't look where those bodies are and this object happens to be very close to the ecliptic plane the plane of the orbit of all of the bodies in our solar system so Tess is actively avoiding looking at this area of the sky for now and it probably won't be able to get there until extended missions in the future when the orbit of the spacecraft is favorable for it to look in this part of the sky and not have Earth or the moon come in and swap the detectors I see now are there any other instruments including coming instruments like the LSST that will be useful in studying this yeah so the challenge with other instruments on the ground is that the transits are very shallow when Kepler detected them it was only about 200 parts per million it's basically impossible to they get that kind of precision from the ground now if the dips were on the secondary star the fainter star then they would have to be much bigger to produce an average depth of 200 parts per million and that actually might be detectable from the ground so one thing that we could do is we could use the ground-based telescope that has better spatial resolution that takes sharper images than Kepler did and we can look for transits of the fainter star and see if there are transits corresponding to large planets on that star and if that's the case then that a tells us which star it's on and B gives us a path forward to maybe unlocking some sort of pattern and the timings of the dips or some sort of periodicity if the transits are on the primary star though then we really have to stick with spacecraft so Spitzer would be an option but Spitzer is about to reach the end of its lifetime in about six months the European Space Agency is about to launch the Chaos telescope which may be our best bet and if we really think we understand something and we can try to predict when we might see a transit we could use something like the Hubble Space Telescope for the James Webb Space Telescope the problems with using those two is that it's really hard to get a lot of time on it and if we didn't know when to look ahead of time it would be very difficult to convince other astronomers that we should spend a month of Hubble time looking at this one star when we don't even know whether we're going to detect anything that will help us understand the mystery it's rather unfortunate I missed the Kepler spacecraft I think we should have manufactured them and sent a whole bunch of them out looking at do an all-sky Kepler survey that would antastic yeah because I doubt of all of the emissions of the last decade Kepler really yielded a lot of mysteries yeah you know very strange stars and and how many exoplanets did it discover like 2,400 something like that oh yeah so it's a resounding success for a commission that really wasn't that expensive compared to others absolutely now with HD 139 139 there is one last option and it's the very last option the bottom of the barrel that you don't want to go to unless you absolutely have to which is SETI is there a SETI possibility with a star is it is it could this be something completely out there I would have to say there's no reason why it couldn't be and you could even tell yourself a nice story about why it might be as you said it's kind of our last-ditch possibility you know we astronomers have a long history of finding something weird like pulsars like Voyager on star scratching our heads over it not having a good explanation and then thinking oh well maybe this is some sort of extraterrestrial civilization and then realizing later no no we have a good natural explanation for this and we can figure out what's going on I suspect that this star will be another one of those cases but in the meantime I think it's perfectly acceptable to consider the SETI hypothesis absolutely and it reminds me when you and this is entirely speculative but it reminds me of Luke Arnold's paper with you know he described back in the 2000s this idea of transiting structures that are just obviously appear artificial like a louver or something like that that can be picked up in a light curve right now my thought is well what if you make the appearance of an impossible star system would you know presumably alien astronomers see that with their Kepler spacecraft and say that can't happen in nature that has to be artificial is that a possibility here I think it's possible I think that the Arnold paper focused on unusually shaped objects which would give you transits that don't look like planets in this case they actually do look like planets to the best of our ability to tell maybe with even higher precision data than what Kepler was able to give us we could have noticed some unusual behavior at the very beginning or the very end of the transits which could have distinguished circular planets from I don't know triangular or star-shaped structures so it would have to be a little bit different from that hypothesis as well yeah I could imagine that this kind of thing could be some sort of like signaling beacon if you can build stuff like that it would probably be a lot cheaper to leave that in orbit for a long time than it would be to continually broadcast radio signals yeah specially if you have brought you're blasting out omnidirectional signals in a couple a contact and you know that just takes a massive amount of energy but if you just made something look weird you know whether it's just a star system that physically shouldn't exist without technology or something like that so but but there's no indication of that yet we're not to that stage yet but it's interesting to think about yeah for sure now another striking thing about this is the randomness of the star system as though it these planets were passing could have been generated by a random number generator how does that play in yeah really that is just a statement of our inability to find any period a lot of things can approximate a random number generator and this thing approximates it very well but we only have 28 dips so it's not very strong for us to be able to say that it is random probably there is an underlying pattern we just can't find it with only 87 days one other question regarding the study possibilities if it were something like that what would you look for to try to determine that's what that was it would you look for some sort of pattern long term you know in other words study the star for a year and see if there was anything there or would you try to get spectra of whatever these objects are how about how would you go about determining or say they were planets actually say say there were planets and you you wanted to study the planets themselves and try to work out what their atmosphere might be like how would you go about doing that with a star so the first thing that I would do if I had the resources to do it would be to build a new Kepler to go and observe the star for much longer than 87 days so in the original Kepler field we had data on stars for four years now after the mechanical failure that ended the original Kepler mission we only were able to observe stars for about 80 or 90 days at a time I think that if we had been able to observe the star or maybe for years we might have been able to detect some patterns we might have been able to figure out what was going on so I had the resources to do so I would just keep monitoring the star record all the times of dips and just keep doing the tests that we did in this paper until some signal starts to emerge from the noise then if their planets and we think we have the period you can come in with more powerful instruments like Hubble or James Webb you can look at the spectra of their atmospheres to try to figure out what was going on it's just very difficult to deal with objects where you can't predict the next event it makes everything a little bit less efficient instead of being able to come in with James Webb and spend maybe a couple of hours when we know the trance it's gonna happen you would have to spend you know days on average there were about three days between each transit which is pretty if you want to spend a lot of time with James Webb you have to observe for several times that to guarantee with some high probability that you would find in events one thing that went speaking of chaos eight four six two eight five two that star they crowdfunded observation time on I suppose private telescopes yeah is this possible to do it with HD 139 139 it's possible we could try to observe it from the ground using the same telescope Network as voyage on star unfortunately the small depth of the dips would hurt us there as well if we found out that the dips were on the fainter star then that would open up that possibility quite a bit and we could do something exactly like voyage on star and try to just pin down as many dip times as we could and maybe eventually quite in the period now in terms of these dips being shallow how much four percent is the drop in overall light I know with Biogen star it was like 21% or something like that but in this case it's much smaller so percentage-wise what's it like it's about 2% of 1% it's also very dim so yeah very very area 200 parts per million I see now how big are these the SI their planets how big are they I mean are these earth-like sized planets and I know if they're around one star they're gonna be Jupiter size but say they're on the other star how big are they gonna be and are they within the habitable zone of the star if you can tell yeah roughly they would be about one and a half to twice the size of Earth which is a fairly common size for planets we've found with the Kepler telescope that these super earth sized planets are some of the most common planets in the galaxy based on how long it takes for the transits to happen what the duration of the transits are I would guess that most of them are probably too close in to be in the habitable zone but maybe some of them could be in particular there's one dip that lasts at eight hours that's getting to the orbital speeds that we expect for a planet in the habitable zone now one odd aspect of this is that if you were in this star system HD 139 139 and you turn to your Kepler spacecraft towards the Sun you would see our solar system transiting right which would put it that's right sitting like half a percent of of the galaxy that's correct it's interesting it's that's one of the things that you could use to make a really nice steady case if you wanted to yeah they look and they see this beautiful exoplanet earth and they're like well it's orient something towards them and send them a message yeah out of how many stars within Kepler's second mission field of view how you know is this one out of how many that you saw that showed patterns like this yeah in the second mission there were probably three hundred thousand stars observed and as far as we can tell there wasn't there were no other stars like this it's a little bit hard to say that for sure though because this was not found by computers this was found by humans citizen scientist looking through the data by eye and what's great about humans is that they learn as they go along but that doesn't necessarily mean that they were looking for this very early on in the mission maybe they wouldn't have seen it if they come across it so it's possible that there are other objects like this in the dataset that the citizen scientist may have passed over the first time they saw it and then as they learned more about the data and what was interesting may have passed it along to professional astronomers like myself when they saw it at the rel very fairly close to the end of the KT mission when this object was observed now what was the citizen science project that found it was at the planet hunters that I know they found Biogen star yeah so this is a group working independently I believe they all started out on Planet hunters and they learned very quickly what was interesting and soon the planet hunters online interface just wasn't enough for them and they started writing their own tools they have this freeware package called Elsi tools that lets them very easily click through like curves very quickly and look at them and zoom in and measure things it's a very impressive operation and there's about ten or fifteen these folks who just do this and whenever they find something interesting they shoot astronomer select myself an email and say hey look at this I think it's a I think it's a wonderful thing because astronomy has always been something where the amateurs could help the professionals back in the day with people searching for comets with telescopes a lot more just amateurs with with telescopes yeah and now in the computer age we can do much much more and that sort of symbiotic relationship continues so one last question before we go say that this if you had if you had to make a bet what explanation is the best the the sunspots and if you had to make a bet is that do you think that's really what it is if I had to make a bet I would go with my first and state when I first saw this like her I said this is a multi planet system and even though it seems really hard and contrived to make that work the transits looked too normal for me to believe that some sort of dusty thing we've never seen any indication that the star spots can appear and disappear the way it would need to in this case none of the other explanations feel writes me other than something to do with the transiting planet there may be a twist there may be a binary planet I don't know some sort of weird architecture maybe some sort of glitch like a flare and the star that happens at the time of transit which made us miss one something weird may have happened but my guess somehow the final explanation will end up looking like a normal transiting super earth around the primary star should the various study programs turn their radio telescopes to this star I think so SETI is by its nature a high-risk high-reward observational program I would say that looking at stars like this has very little downside for them if they find nothing then they mark that star off the list there are lots of other stars but I think this one has a much better reason than most other stars in the galaxy for them to look at it so I would say why not if we find it if we find something there then it's you know the greatest discovery in the history of our civilization so what is their loose nothing to lose and even if we don't find it we still have one very interesting star system that's going to teach us about something new absolutely well thank you for joining us doctor and good luck with your research thank you for having me this has been a breaking news story from event horizon be sure to subscribe for updates on this as well as regular guest interviews every Thursday [Music] [Music] [Music] [Music]

Channel: Event Horizon

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Rating: 4.864471 out of 5

Keywords: tabbys star, 8462852, alien, seti, extraterrestrial, wow! signal, hd 139139, megastructure, astronomy, science, godier, event horizon, kepler, drake equation, fermi paradox, universe, space, NASA, oumuamua, exoplanet planet, mystery, technosignature, biosignature, dyson swarm, EPIC 249706694, The Mysterious Star HD 139139, saul rappaport, Dr. Andrew Vanderburg, event horizon john michael godier, bizzare star, The Random Transiter

Id: Ml8BsjSdPWo

Length: 30min 36sec (1836 seconds)

Published: Tue Jul 09 2019