Speaker 1: 00:00 They are known as cosmic monsters and are some of the most extreme objects known in the universe. They are starred on the verge of collapsing into a black hole, a celestial event. So extreme the conditions, defy physics, and can't even be recreated here on earth scientists, call them neutron stars and they have gotten their first glimpse at one through the NASA telescope. Joining me now is Cole Miller, a nicer team member and professor of astronomy at the university of Maryland Caldwell. Speaker 2: 00:29 Awesome. Thank you very much, Jane. Thank you for having me. So can you explain what a neutron star is? You think about a really big star, a lot bigger than the sun and it lives a fast life. And then when it dies, it dies spectacularly, it collapses, but if it becomes a neutron star, it stops collapsing when it's about the size of a city. So it has a surface and it's hot and nasty. And luckily we're far enough away from these that we can study them from a safe distance. Wow. Okay. Speaker 1: 00:57 And you know, it said a neutron star is a black holes, smaller cousin, right? Speaker 2: 01:01 Why is that? It's because if you think about even bigger stars, which collapsed, they collapsed all the way. They don't stop the size of a city. They'll go all the way down to a point making a black hole. And instead of surfaces, black holes have a distance from that central point such to the, if you get inside of it, you're not coming back out ever. And black holes are heavier. The neutron stars, which I suppose makes them the larger cousins of those neutron stars. Wow. Speaker 1: 01:28 So what relationship do neutron stars have with space and time? Speaker 2: 01:33 Well, neutron stars because they tact such a huge amount of matter and such a small volume work space and time in a way that was originally envisioned by Albert Einstein. This means for example, that if light goes by them, it bends a lot, a lot of other very strange things, but this is precisely the kind of science that we are testing with masses, nicer mission. Hmm. Speaker 1: 01:55 What's your role? Uh, on the nicer side Speaker 2: 01:58 Team, I am the leader of one of two teams, which have analyzed the nicer x-ray data, which have been taken on us select number of neutron stars, where we're trying to use this information to figure out the sizes of neutron stars. And the reason we do that is that gives us a hint about the state of the matter in the inside of these stars, which is a state we cannot probe and laboratories on earth. Speaker 1: 02:22 Why do scientists want to find out what the core of a neutron star is made of? What can it really do? Speaker 2: 02:28 It can tell us about a state of matter that we don't really understand. Not only can we not experiment on it in laboratories on earth, but various series as diverged wildly about it. Indeed, I would say quite generally, because neutron stars represent extremes in matter energy and gravity, any study of them leads to the possibility of truly fundamental improvements in our understanding. Speaker 1: 02:51 I mean, when we've tried to recreate those conditions here on earth, but what I guess I'm wondering like what happened when we got close, we have gotten Speaker 2: 03:00 Close only in a couple of ways. One is that if you think about ordinary atoms and you may remember that these have nuclei of neutrons and protons in them, that's a state of matter, but it's not as dense as you get into the neutron star. You could also slam nuclei together at very high speeds, but that's much hotter than a neutron star. So this is really off limits. The only way we could manage this on earth is if we had some supernatural giant who was able to crush things to an extraordinarily high density. And so far we haven't had any such giants volunteer. Speaker 1: 03:33 So the large Hadron Collider just didn't even get us close. Speaker 2: 03:36 No. And that's because you ended up with matter. That's very hot as well as being very depths for the neutron star. It's very dense, but actually by the standards of these things relatively cold, the temperature doesn't play much of a role. Speaker 1: 03:48 Interesting. So, I mean, so when, when these stars collapsed, what do you, what type of matter do you think they turn to? Do you think they turn to plasma? Speaker 2: 03:56 There is a very good idea that in some case they are considered to be not just a plasma, but one is made up of the components of neutrons and protons. So this is corks and glue-ons and plasma. But what we know for sure is that this satisfies the conditions of the plasma. It's fully ionized. The electrons are just moving kind of randomly without being attached to individual nuclei, but it's okay. Say it is so puzzling about what's going on. Then we need these observational hints, like was nice. Speaker 1: 04:26 And can you go more into what the telescope allows to be seen? Speaker 2: 04:30 Yeah, nicer is an x-ray telescope. And because very fortunately for humanity, x-rays do not get through the atmosphere. It means you must have x-ray telescopes above the atmosphere nicer as one of those it's mounted on the international space station, which has a lot of advantages that the infrastructure for power, for data relay down to earth and so on, it is all very positive. And so what nicer is doing is it's specializing, it's looking at a select number of targets and staring at them a lot. So for this one, it's about 1.6 million seconds of total exposure over two years. And this type of staring at the sources is essential to get the data of the quality we need. Speaker 1: 05:13 And that gives us an idea of what that core is made of. Speaker 2: 05:17 It does, although somewhat indirectly, the key is that by these x-ray measurements and then our own work on inferring, what it means we're able to get a good estimate of the size of neutron stars people have tried before, but these have often been methods that have been subject to possibly very significant bias for various reasons. We think that is not true for these measurements. Knowing the size then gives you kits where we can go to physicists and say, what does this imply? So it allows us to tell things about the nature of the matter, how squeezable it is, for example, but there's still some mysteries that await further data. Speaker 1: 05:54 And what else can be learned from being able to see neutron stars? Speaker 2: 05:58 Neutron stars in general are objects that have many extremes. They have the strongest magnetic fields in the universe. They're the best natural clash in the universe and sign it just as an example of one of the remarkable things that people are working on. You know, that gravitational waves ripples in space time has been seen by instruments such as Lego, but what's not been as publicized is that people are using a raise of neutron stars to use them as these outstanding natural clocks. And there may be getting the first hints and expect to see them within five or so years that we have ripples going on with much longer periods. So actually seeing the symphony of the universe using pulsars as natural detectors. Speaker 1: 06:40 Interesting. What exactly is a ripple in space time? Speaker 2: 06:43 The things that comes out of, I am science theory of gravity, which is general relativity, is that if you have things that are moving, then the normal warp of space time, think about a bowling ball on top of a rubber sheet. If you move two bowling balls around, there will be ripples in that rubber sheet. And in space and time, these ripples are called gravitational waves. If they were to go past you, they would stretch and shrink you, but by my Newt amounts, so we need extremely sensitive instruments. So why does this matter? I think that there are various reasons why this matters. I'll give you sort of the, uh, the high-minded one and that also a practical one for the high-minded one. We want to be able to learn more about matter and energy and gravity. And this is a case where we can't do the studies on earth. Speaker 2: 07:29 And so this is the only way we get that info in terms of practical import is something, a lot of people don't recognize is that the scientific motivation for a particular project, such as this one often requires the development of technology, which is useful in other ways, nicer, for example, is not just being used as study neutron stars. It's used also as a pilot study for using the extremely well-timed pulsars that I mentioned that the neutron stars are did are great clocks to potentially in the future, navigate around the solar system, kind of using those neutron stars as natural GPS. And that's because of the drive toward being really able to time extremely well when individual x-rays arrive to us, that this has become possible. Speaker 1: 08:15 Very interesting. I've been speaking with Cole Miller, a nicer team member and professor of astronomy at the university of Maryland Cole. Thank you very much for joining me. Speaker 2: 08:24 Yes. Thank you very much. Jayda pleasure talking with you.