 Hello and welcome to the OIST podcast, bringing you the latest in science and tech from the Okinawa Institute of Science and Technology Graduate University. This episode we're looking up into deep space as I'm joined by astrophysicist Dr. Samaya Nassanke of the University of Amsterdam's Centre of Excellence for Gravitation and Astroparticle Physics or Grappa for short. She is also a joint faculty member at the Anton Panicook Institute and the Institute for High Energy Physics. Dr. Nassanke was recently a guest speaker at OIST, where she lectured about conducting a scavenger hunt on a truly cosmic scale, using a global array of telescopes to detect the gravitational and electromagnetic waves that get released when pairs of black holes or neutron stars develop binary orbits. Events where two of these astral objects swirl around each other before merging together. But what secrets do cosmic events like these hold? How can we detect them in the vastness of space and how did a neutron star collision upset a family holiday? All will be revealed as I sit down with Dr. Samaya Nassanke. Thank you for coming and joining us and welcome to Okinawa. Thank you very much for having me. Thank you. It's a pleasure. First of all, for people who may not be familiar with you, imagine you have to describe yourself and what you do at a cocktail party. How would you say it? Well, I'd say I probably have like one of the most extremely privileged and fun jobs that one can have. Obviously, this is talking from my own personal opinion, but yeah, I get to basically study the most extreme and exciting events that happen in the universe, essentially colliding and merging black holes and neutron stars and get to study them using gravitational waves as well as electromagnetic radiation. So this is a really new exploding field of research thanks to the discovery of gravitational waves that happened four to five years ago. And so, yeah, it's a wonderful sort of time to be a scientist and to be a physicist and to think about basically the extremes of space time. OK, now you came to OIST today to give us a little lecture about your work on binary neutron stars and how they kind of spin around each other and eventually kind of merge into one object. But can you take a step back for us who aren't quite up to speed on our space tech? What is a binary neutron star? So binary neutron star is basically a pair of neutron stars. Neutron stars are the end states in the lives of massive stars. And typically why we're interested in them, they really are sort of the most extreme matter and space time objects that we know of. And so typically they have masses of one point four to three times the mass of the sun and they're crammed into radii of about 10 to 15 kilometers to the size of basically Amsterdam, where I'm living at the moment. And therefore their nuclear densities are a few times the nuclear density in the cause and their densities are as high as if you basically crammed the entire of humanity into a sugar cube. So they're really the most extremely dense objects that we know of. They have sometimes magnetic fields a hundred trillion times of that of the earth. And so they really allow us to basically have these wonderful cosmic laboratories and by studying pairs of neutron stars that are essentially kind of doing a sort of death in spiral dance around each other due to the emission of gravitational waves. You can really explore what's happening in strongly curved space times where you know really the dynamics are being driven by general relativity predominantly and then also really study how matter behaves in these extreme space times. So they're really sort of unique cosmic laboratories and in some sense astrophysical colliders. This is not something we can really observe through a regular telescope. For example, yeah, so we know we have postulated basically that we should emerging neutron stars should basically be producing, for instance, short gamma ray burst. These are bursts of gamma rays that we've been observing for decades now, which typically last for about two seconds. And so the leading model has always been that pairs of neutron stars merging are producing these as well as actually that these are because of the thermodynamic conditions, you know, the extreme densities, their temperatures, et cetera, the right sort of conditions to actually produce all the heavy elements that we have, for instance, on the earth. You know, they have been long postulated that merging neutron stars should produce a mission in terms of light. So basically gamma rays, optical, the ultraviolet, the infrared. For the first time, we were able to actually sort of confirm this hypothesis. With this binary neutron star merger that was observed in August 2017 in gravitational waves. So tell me a little bit about that day. What what happened from your perspective? Well, so that day basically was very memorable because it was in the middle of August, so sort of summertime in Europe. And we had had a few day workshop in Amsterdam about the future of gravitational wave astronomy. There was a lot of excitement because a year before, you know, that being the announcement of the first binary black hole merger that have been detected in gravitational waves with the two LIGO detectors. And, you know, so there was a real sort of feeling that, you know, there are more events going to be happening. There may be our first gravitational wave merger that may involve neutron stars, you know, this may be upcoming. Precisely when was very sort of unclear. And in this workshop, I was asked to give a talk about the future of multi-messenger astronomy in the 2030s. And so when I gave stood up to give this talk, I said, we have to talk about what, you know, what will be the state of sort of multi-messenger astronomy in the 2020s. So by multi-messenger, I'm saying where we can observe both the gravitational wave and electromagnetic radiation. From merging black holes and neutron stars. And I made the claim that there would be several of these mergers occurring. In the 2020s, and several people put their hands up and said, oh, this is, you know, very optimistic. I myself, at the lunchtime of that workshop, had a discussion with a well-known Indian analytical relativist, the head of the Indigo consortium there, Balaiya. And he had mentioned to me, oh, you know, he really liked my optimism, but he was doubtful that we would see a binary neutron star before 2020. And I actually took a bet with him, a sort of gentle man, gentle woman's sort of handshake bet and said, well, actually, I think we probably will see one. I don't know what gave me the confidence, but an hour later, I was actually looking at the time frequency spectrogram of the first binary neutron star, where you could clearly see that there was a signal that we predicted, the so-called chirp signal appearing that was due to these two neutron stars actually merging into each other and emitting this burst of gravitational waves. So I remember that day very clearly. It was definitely a moment where I took several kind of deep breaths and it was just like, whoa, that's completely nuts and completely unimaginable. Very good timing for the bet. Very good timing for the bet, but very bad timing, I think, for my family's holiday. So we were supposed to go on holiday the next day. Yeah. And I would say I was not the most popular person for the next few months with my husband and one year old son at the time. I'm sure they'll forgive you in time once they realize the cosmic significance of it all. So I think you're using these these extremely advanced telescope detectors. I guess they're they're picking up on gravitational waves and electromagnetic waves that are kind of coming down from the cosmos and striking them. What what is the kind of broader significance of that in terms of our exploration of space or exploration of physics? What does this mean in the broader term? What questions are you trying to answer? So I think there's a variety of questions that are now being kind of posed as well as we're able to actually answer by having these kind of empirical measurements. And interestingly, they're happening sort of in several diverse fields. So I would say we can use these neutron star binary mergers as well as neutron star black hole mergers systems, basically as standard rulers in some sense to map out the local expansion history of the universe. So using these as kind of cosmological probes. This is one very interesting avenue. The second interesting avenue is in nuclear astrophysics. So understanding how heavy elements are produced in the universe, I think is obviously, you know, a central question that has been driving kind of understanding. Yeah, where we come from this very central question. So nuclear astrophysics as well as understanding, for instance, the equation of state of neutron star. So what happens to extreme matter in extremely curved space times? Another question is obviously, you know, what happens to the in the death of basically pairs of massive stars? So understanding how most massive stars that we know of exist in binary systems in pairs, basically. So understanding what happens in the lives of these systems can be answered by looking at the end states, you know, how these systems are forming, how many where they're forming, as well as just generally understanding the mysteries of high energy astrophysics phenomena. I've already alluded to things like short dam rebus, but these have been really long standing questions over decades. You know, what actually causes, you know, these at the time, and, you know, in some sense, still quite elusive, kind of highly violent, highly transient events. And so really understanding things like how do relativistic jets form, accretion disk physics around black holes, even neutron stars. So these are all questions that are being answered. And also just using these as sort of test beds for testing general relativity, as well as just our standard model of physics, particle physics. So it's a really big sky up there, basically. And you alluded to this in your talk. There's so much out there that you could be pointing a telescope up from like super elevated like regular black holes to perhaps even just gas patches. And how do you find the needle in the haystack of these binary collisions? Excellent question. So I would say that there's been tremendous progress basically in the last 10 years. Not only have gravitational wave detectors actually come online, but in terms of traditional astronomy using sort of your optical telescopes or your radio telescopes that we've grown up with and grown to love. We've now entered this new era of time domain astronomy. So we're no longer just having snapshots of the sky, but we're also continuously monitoring the sky in terms of being able to build up a movie or a multicolored movie. And this is happening now with several telescopes, as well as future telescopes such as the such as LSST, the Large Synoptic Sky Telescope Survey Telescope. And so in terms of actually pulling out the needle of the haystack for this one event, it was actually quite straightforward in the sense that we were very lucky that the first sort of transient that was seen when compared to archival images was actually the real deal. And this was really sort of continuous monitoring and spectroscopic follow up that showed that it was unlike any transient that we'd ever seen. Or unlike any others kind of supernova. But in terms of actually doing it now in practice where the signals are less strong, the sky areas are much bigger sometimes. It is this needle in the haystack problem. I actually used to call it the Wears Wally problem for those who grew up in the UK or Wears Charlie in the US. What's the name in Japan? A Waldo. Okay. Do you know the name in Japanese? I don't know if it's actually made it to Japan, at least. Oh, no, no, it has. Okay. Wears Wally, but I will find that out. Yeah, one for my research. But essentially now a lot of it's happening thanks to machine learning algorithms as well. So basically being able to say what are actually instrumental artifacts that are happening when you are subtracting, you know, real time images with archival images and saying, okay, these are actually astrophysical either galactic events that are happening or else extra galactic supernova. And then you can characterize these using kind of known light curves or machine learning algorithms. So it's really becoming this sort of big date in astronomy problem. And also obviously this impacts just the sort of wider field of time domain astronomy. What's a good day for you and work? What really gets you fired up to get into the lab or into your data sets? So in the last six months from the 1st of April 2019, the LIGO and Virgo detectors began their third science run. So I would say what has kept me up a lot in the last six months are obviously the new very exciting alerts that are being sent out that for systems particularly that may contain a neutron star. So a neutron star or in particular I'm really excited about the prospect of a neutron star black hole merger happening, which we have yet to actually detect both in gravitational waves and electromagnetic waves. And so I think for me, that is sort of the scientific aspect where my group will get inundated with messages from me about what's going on, what's happening and updates from there and also what are the interesting signs that we can potentially learn. And then I think overall it's interacting with my fantastic group in Amsterdam. I have a wonderful group of postdocs and PhD students and master students and definitely discussing science with them is the thing that I think puts a big smile on my face and I feel just super lucky and super enthusiastic and especially on the way home on the train. I have a big smile on my face after those kind of days. So you kind of touched upon this a little bit, but I guess now that you've found this, the next step I guess is to try and locate, you said the neutron star black hole merger. Well, can you describe it a little bit like that? What would, what am I trying to say? So I guess for the neutron star black hole discovery space I think it's going to be very exciting because these systems are in some sense more asymmetric than, you know, a pair of black holes merging or else a pair of neutron stars. You have a mixed system and neutron star black holes. So there's more asymmetry. The black holes themselves may have significant spin. So basically angular momentum, their own intrinsic angular momentum and maybe spinning in different orientations. So as a result, we may from the gravitational wave side actually learn a lot more information about the actual masses, the intrinsic properties such as the spins as well of the neutron star and black hole as well as potentially about the equation of state of the neutron star and from the electromagnetic signature. Similarly, we may also learn quite a lot more just because there's in some sense cleaner systems. And so I think that for me is sort of the immediate kind of thing in the next year that I'm really excited about in a more kind of forward looking sort of five to 10 year scheme. I think, you know, we've really been focused and now for a decade or a couple of decades on kind of the discovery era, what will happen with the first detections. We've had that will happen with the first discoveries, the first few events. But you know, we all have already entered this kind of era where these events are happening routinely, they're being detected routinely. And that I think is just an incredible opportunity for so many different fields. I've already listed nuclear astrophysics, cosmology, extragalactic astronomy. And so I think, you know, that is the era that I'm really excited about is using these systems also as probes, for instance, to understand large scale structure, how the universe itself came into play. And that, for me, is also very exciting, as well as obviously just the fundamental properties of understanding the nature of black holes, yes. So in many ways, a lot of what you're doing now, assuming that we eventually travel out into the stars will be like the groundwork for very, very long range space exploration. A little bit, perhaps. I mean, it's possibly a little science fictional, but... I've never myself wanted to go into space, but I do, yeah, I mean, I, you know, I think thinking about the universe, you know, it always does make you wonder at the incredibleness, yes, of the universe. And so I think some, yeah. Just a little bit. So, I mean, stepping back a little bit back to the start of your journey into science, was there any kind of an inciting incident for you? Was there something that really gripped you and made you think, I've got to study this? Or was it something that happened more by degrees? What was your story of getting into this field? Yeah, I think firstly, thanks to my father, he was, yeah, he was really wonderful in terms of explaining to me about the solar system and things like this and visiting museums and the planetarium, the science museum in London, I remember going to as a kid. I did a school project when I was seven on the planets in our solar system. I remember that. I was like, wow, this is so fascinating and just being completely excited. I really loved mathematics. So actually I wanted to be a mathematician when I was growing up. But about the age of 16, when I went to high school, I was incredibly fortunate to actually have physics teachers that I'm still in touch with high school teachers. And who were just fantastic, inspiring. They made studying physics, I think, just such a joy. And I did a summer project on, I think, the mathematical models of the universe. And from that instant on, I was like, I really want to become an astrophysicist. I really, really would love to be able to spend my time studying the universe. And so I think that, yeah, from the age of about 16 to 17, I was incredibly fortunate to have found something that I just loved doing. Excellent. Now, 2019 it may be, but we're still very, very far behind in creating a level playing field in terms of gender equality in the STEM field. And I just wanted to get your opinion on what the state of things are now and how you think we could perhaps improve things in the future. Yeah, I think that's a really important question. It's very clear to me, especially now, that having kind of excellence in science and in physics and creativity comes from having a diversity of different minds, different backgrounds and different scientific questions, I think, opposed by having a diversity in terms of scientists. And so it's not only actually gender kind of equality, I think, that I find see as a challenge, but also other kind of underrepresented minorities in physics. I don't think we do a very good job at all. And maybe even worse, because there's still some kind of reluctance and hesitation to discuss certain aspects where I think we are not doing so well in terms of underrepresented minorities, especially in Europe, I see that. But I think the, at least on the gender front, we, you know, the good thing in the last 10, 20 years since I was a student myself has been that the discussion is very open now and that also there are now quantitative studies and that, you know, I think universities at all levels are very engaged in trying to address the issue of gender equality in STEM. And so as a result of this sort of awareness, increased awareness, you know, there are now very interesting initiatives where the kind of prevailing view before had been that, you know, you have to hire maybe a few more women, professors and faculty, and somehow the system would automatically, you know, find a solution. We now know actually, yes, that may happen on the sort of decades, long timescale, but in terms of addressing it in kind of the 10-year timescale, you know, we need to actually be much more active. And I mean, by we, I'm talking about both men and women, physicists at both the senior and the junior kind of level is really ensuring that at the high school level, at the, you know, university level, as well as not just doing PhDs, but going on to the postdoctoral level where I see often a very big leaky pipeline happening is that we have sort of sustained mentoring, sustained support, I think, both on a practical as well as on a professional kind of mentoring level. One aspect, for instance, just an I myself have faced is actually having a young child, you know, does impact one's scientific career and output quite significantly. And I think by having the openness and the directness in these conversations, you know, it does, it is improving things, but it does really require sort of concerted effort. And I see this also now in terms of other underrepresented minorities that however uncomfortable the discussion, you know, it needs to be had because this is how to really achieve kind of excellence in physics. So someone who's definitely at the top of their game in their field right now, do you have any advice for somebody who might be starting out their career in physics or a young researcher or undergrad? Is there any one bit of advice that you have received that you've taken with you on this journey? So I think on a very basic level, I think the most important thing is to always remember the love and fascination that you have in physics or in science, you know, we get a lot of, there's a lot of discussion now about how hard it is to find a kind of career or permanent job in science, but I think it's really important just to remember kind of the general joy of doing science, of asking questions. One piece of advice I would have is to really say, never stop asking questions. Yes, however basic they may seem, they're not. Yes, always go back to just, you know, your scientific curiosity, what I think makes a lot of people go into science is just this question that my three-year-old is now becoming very good at just saying, why, why, why? Almost several hundred times a day, but it is true, I am beginning to once again remember, yes, that was how I was too, you know, why? Why does this work? Why does this happen? Our whys become more sophisticated. Our whys become more sophisticated, but at, you know, the kind of fundamental level they're the same, so to keep that. Secondly, I would also advise to seek out mentors. I was really fortunate that not maybe in my own field, but in other fields of astronomy and cosmology, I had the privilege and the good fortune to meet really impressive both women and men, physicists and scientists, and many of them, well, several of them really had a defining impact on my own view of my career. I think, you know, there were several times before gravitational waves detected were discovered that, you know, it was looking very unclear as to whether I would find a permanent job doing gravitational wave astronomy. And I think determination is also very key, yes? Do not kind of lose hope and love what you do, I think. And also, yeah, sometimes research is tough. Yeah, there will be months sometimes where you are just stuck and it's really frustrating and, you know, you get, you feel a bit down in the dumps, but that is part of research. And then, obviously, they're completely compensated by the moments where, you know, you suddenly understand something or you observe something or you just see, you know, you make empirical measurements, for instance, in this case of binary neutron stars merging, and it's just absolutely incredible, yeah? Brilliant. And just to wrap us up, I'd like to ask this of people that we interviewed. Is there a question that you really wish someone would ask you? And if so, what's the answer to it? Is there a question I would really wish someone to ask me? Yes. Oh, I don't think I've ever kind of thought about that, yes? And I don't think I have an answer. I'm always kind of open to having, yeah, I think that's the nature of science, is that you want questions that you haven't thought about, yeah? And that you want to maybe not know the answer, because that may be sort of the next adventure in your scientific career. So I think in that sense, no, I have never had a question I've wished people have asked me, because, yeah, I love being asked questions, and I also love actually not knowing the answer, because often I go home and will spend, you know, time, I don't know, yeah, at night, or I don't know, in the bath, thinking about it, and it starts me thinking, oh yes, that's true, I've never thought of it this way, this, you know, and that kind of thing. Okay, one alternative then. What's a question that's keeping you up at night at the moment? What's the question that's keeping me up at night at the moment? I guess, fortunately, I have a three-year-old. So no, so I really value my sleep, so in that sense, I do manage to sleep quite well, because I'm normally pretty exhausted after a couple of years of sleep deprivation, but yeah, I guess, you know, do we understand physics, you know, things like general relativity, the standard model of physics, particle physics, things like lambda, CDM, our cosmological model of the universe, you know, there are kind of interesting suggestions and hints that, you know, we don't have a complete picture, so I think, you know, what's exciting is to think about how gravitational waves may play a role in answering some of these questions, so I think those are probably the things that I do like to think about, just taking a few steps back from kind of my everyday job. Okay, right, so just about to wrap up, but is there anything else you'd like to talk about? Yeah, I think essentially, you know, I've been delighted to be visiting OIST, I mean, my mother is Japanese, so for me, it's a real privilege to, whenever I come back to Japan, where I spent many, many summers growing up, to come and visit Japan professionally, and also to see what's happening at places like OIST, where there's just such vibrancy and dynamic kind of interaction, the students and postdocs that I met at lunch were, you know, really fantastic and open, and so that gives me, yeah, I think that really, um, as someone who's half Japanese, I really see, you know, the scientific environment in Japan, thanks to places like OIST, it's really also changing and very exciting for the future of science. Samai Anasanki, thank you very much. Thank you. Thanks for listening to the podcast. It was recorded and edited by me, Andrew Scott. Special thanks to Dr. Samai Anasanki and to Professor Reko Toriyumi. If you enjoyed this episode, why not subscribe to get more as soon as we release them? And we always love to read your reviews, so why not let the world know what you think of the show? You can also find us on Facebook and Twitter, or send us an email to media at oist.jp. Thanks again for listening. See you next time.