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  • NATURE PODCAST

Podcast: 'Sticky' RNA, disorganised taxonomy, and 'intelligent crowd' peer review

This week, 'sticky' RNA causes disease, disorganised taxonomy, and 'intelligent crowd' peer review.

In this episode:

01:03 RNA repeats clog cells

Some genetic diseases are caused by repeated chunks of DNA. How? Research paper: Jain and Vale; News and Views: RNA repeats put a freeze on cells

07:10 Organising the organisers

Taxonomy – the science of classifying species – is in chaos. Here’s one way to tidy it up. Comment: Taxonomy anarchy hampers conservation

14:17 Research Highlights

Why whales are so big, and where all the antimatter is. Research Highlight: Why baleen whales grew big; Research Highlight: Explosive origins for antimatter

15:58 An intelligent crowd

What if, instead of 2 or 3 peer reviewers, there were 100? World View: Crowd-based peer review can be good and fast; Synlett

22:38 News chat

Juno spacecraft cosies up to giant Jupiter, and new mission to explore the insides of super-dense neutron stars. News: Jupiter’s secrets revealed by NASA probe; News: Neutron stars to open their heavy hearts

Never miss an episode: Subscribe to the Nature Podcast on Apple Podcasts, Google Podcasts, Spotify or your favourite podcast app. Head here for the Nature Podcast RSS feed.

doi: https://doi.org/10.1038/d41586-019-03100-7

Transcript

This week, 'sticky' RNA causes disease, disorganised taxonomy, and 'intelligent crowd' peer review.

[Jingle]

Interviewer: Kerri Smith

Welcome back to the Nature Podcast. This week could the review process for scientific papers be made more scientific?

Interviewer: Adam Levy

We also meet the scientists who accidentally hit upon an explanation for a whole family of genetic diseases.

Interviewer: Kerri Smith

And we find out the scientist whose job it is to classify and organise species – their world is secretly in chaos. This is the Nature Podcastfor June the 1st, 2017. I’m Kerri Smith.

Interviewer: Adam Levy

And I’m Adam Levy.

[Jingle]

Interviewer: Adam Levy

Some genetic diseases, including Huntingdon’s disease, are caused when short DNA sequences are repeated too many times inside particular genes. How these repeated chunks actually caused disease has been a mystery. Kerri spoke to a pair of scientists who stumbled on an answer.

Interviewer: Kerri Smith

It all started with the Ice Bucket Challenge…

Audio Clip: Ice Bucket Challenge

Governor, I accept your challenge… Bring on the bucket… [water sound effect].

Interviewer: Kerri Smith

A couple of years ago, videos of people chucking cold water over themselves went viral on social media.

Audio Clip: Ice Bucket Challenge

That was really cold….

Interviewer: Kerri Smith

Interviewee: Ankur Jain

Yes, so we were using DNA as a simple polymer to understand the process of self-assembly.

Interviewer: Kerri Smith

He and his colleague, Ron Vale, were just using RNA as a toy – a building block – to see how it stuck to itself and formed structures. They’d made up some artificial sequences so they could watch them perform in test tubes. And then the ice bucket challenge happened and Ankur happened to look into what causes ALS. He found out that in some cases, the disease has a genetic cause.

Interviewee: Ankur Jain

And the sequences that we were designing started looking very much like the sequences associated with the disease.

Interviewee: Ron Vale

G-G-G-G followed by two ‘C’s.

Interviewer: Kerri Smith

This is Ankur’s colleague, Ron Vale, also at the University of California, San Francisco. That sequence…

Interviewee: Ron Vale

G-G-G-G followed by two ‘C’s…

Interviewer: Kerri Smith

… Is the one associated with ALS, but in other disorders, it’s other strings of letters.

Interviewee: Ron Vale

So for example, in Huntington’s Disease there’s a simple repeat of C-A-G.

Interviewer: Kerri Smith

Most people have just a few repeats of such a sequence…

Interviewee: Ron Vale

C-A-G, C-A-G, C-A-G, C-A-G…

Interviewer: Kerri Smith

It’s only when the repeats reach beyond a critical number that the disease appears. In Huntington’s Disease, that’s about 30 repeats or more…

Interviewee: Ron Vale

… C-A-G, C-A-G, C-A-G, C-A-G…

Interviewer: Kerri Smith

And here’s the mystery…

Interviewee: Ron Vale

Why is there this critical threshold? Why does it seem that individuals that just have a few don’t get the disease but after that threshold the individual becomes at great risk of the disease.

Interviewer: Kerri Smith

Ron and Ankur figured their artificial sequences could have the answer. There could be some physical property of the repeated RNA strings that’s linked to disease. There are two main theories for how the repeats cause disease. One says that too many repeats make too many proteins and that messes up the function of the cell. The second theory says that maybe the RNA containing the repeats can’t get out of the cell in order to make anything.

Interviewee: Ankur Jain

In ordinary circumstances, the RNA will be made inside the nucleus of the cell and it’s exported out and then translated. If the RNA contains these repeats it gets accumulated in the nucleus itself.

Interviewer: Kerri Smith

Ankur figured he could test with his artificial strings, whether the RNA was sticking to itself and forming a clump.

Interviewee: Ankur Jain

We synthesised an RNA which contains various numbers of these repeats, C-A-G repeated several times. And as a control, we scrambled that sequence to keep the base content the same as the repeating sequence but now the order of these nucleotides is scrambled and what we saw is that the RNA which has the repeats assembles into large clusters which are tens of microns in size, whereas the scrambled RNA is completely soluble. These repeating sequences probably act as tiny Velcro which allows the RNA to interact with one another.

Interviewer: Kerri Smith

That seemed intriguing. But it was only happening in a test tube. So next, they developed a way of looking at the RNA behaving inside cells in real time.

Interviewee: Ankur Jain

And we in fact saw that RNA are interacting and assembling into large clusters behave like liquids inside the cell.

Interviewer: Kerri Smith

This is where they turned to physics and a concept called phase separation.

Interviewee: Ron Vale

Many people will be aware of phase separation – how oil and water separate from one another – that there are certain physical properties that will cause molecules to partition into different phases. So, the whole problem started by asking, as Ankur said: do nucleic gases – can they themselves phase separate?

Interviewer: Kerri Smith

Interviewee: Ankur Jain

Surprisingly it worked really well, however Doxorubicinis fairly non-specific and now we are looking for more specific small molecules which can disrupt base pairing specifically in C-H-E repeats or G-G-G-G-C-C repeats.

Interviewer: Kerri Smith

For Ron Vale, the finding feeds an idea that clumping could be a more general mechanism that causes disease. It’s well known that in other disorders like Alzheimer’s and Parkinson’s, proteins can clump together. Now it seems the RNA is at it too.

Interviewee: Ron Vale

I would say that’s kind of one of the new interesting ideas that the RNA itself may be the driver of aggregation, particularly in these repeat expansion disorders. Neurological disease in some cases may be a protein aggregation phenomenon and what we are saying is that adding to that list, there may be some kinds of neurological diseases that may have an RNA aggregation component as well.

Interviewer: Kerri Smith

Ron Vale, and before him, Ankur Jain, both at the University of California, San Francisco. Their paper is online along with a News & Views: nature.com/nature.

Interviewer: Adam Levy

The Research Highlights are around the corner, looking at big whales and mysterious anti-matter. But before we get to that we’ve got a story all about Taxonomy which is the classification of living things into various groups. So, I’ve got a perfect prop to segue into that topic.

Interviewer: Kerri Smith

You’re holding a plastic in-tray.

Interviewer: Adam Levy

… Shamini’s plastic in-tray.

Interviewer: Kerri Smith

A stolen plastic in-tray.

Interviewer: Adam Levy

Who it belongs to is not the point here. The point is the colour.

Interviewer: Kerri Smith

Okay, well it looks like a kind of dark green, like a bottle green.

Interviewer: Adam Levy

No, no it isn’t.

Interviewer: Kerri Smith

What do you mean, no it isn’t?

Interviewer: Adam Levy

It’s blue.

Interviewer: Kerri Smith

Well, I admit it’s on the blue-y side of green, but I’d definitively say it’s definitively on the green side of the blue-green line.

Interviewer: Adam Levy

Shamini also incorrectly thought that which is why this piece of plastic is the perfect representation of a key problem in Taxonomy: how do you classify things into neat groups when the lines are so blurry? Here’s Shamini Bundell to tell us a bit more…

Interviewer: Kerri Smith

It’s definitely green.

Interviewer: Shamini Bundell

From bird watchers to bug collectors, biologists are often thought of as obsessed with collecting, organising and classifying things: in other words, Taxonomy. One of the basic units of Taxonomy is the species but as a Comment in this week’s Naturereveals, taxonomists don’t necessarily agree on what that actually mean. I called up Les Christidis of Southern Cross University in Australia and asked him, what is a species?

Interviewee: Les Christidis

That’s one of the fundamental questions... I mean, Charles Darwin wrote On The Origin of Speciesbut he never actually answered the question. The problem is, speciation is a dynamic process. We’re looking at a continuum and we’re just trying to put a little square frame about it for each different group of organisms, saying this is a species and this isn’t.

Interviewer: Shamini Bundell

And how do people try and define a species? What are some of the criteria that we use?

Interviewee: Les Christidis

The traditional one was species were sort of self-contained units, so if they interbred, the hybrids would be infertile or have some other deformities. So that was called the Biological Species Concept.

Interviewer: Shamini Bundell

So a horse and a donkey could mate and have a mule offspring but they are then infertile and they can’t make a new species and merge horses and donkeys back together again.

Interviewee: Les Christidis

Exactly, that’s the perfect example, but there are numerous cases where so-called species will hybridise and form not only fertile hybrids but have hybrid zones and then create a continuum in there. Cases like the hooded carrion crow in Europe – quite distinct – but there’s broad hybrid zones between them so the break between species is sometimes leaky.

Interviewer: Shamini Bundell

There’s inconsistencies also, isn’t there, in the way that different animals and types of animals are divided.

Interviewee: Les Christidis

That’s right, and we’ve also got the issue of different species concepts. So, in mammalogy a classic case is the tiger which is recognised as a single species and at the moment there are five or six sub-species within the tiger. Under a phylogenetic species philosophy, subspecies are not recognised, so we would suddenly have 5 or 6 species of tiger.

Interviewer: Shamini Bundell

And why does that matter? Isn’t this just semantics?

Interviewee: Les Christidis

It makes a big difference then because you’ve suddenly got conservation efforts trying to save six species of tigers. It’s okay to say we need to save the tiger which everyone would agree and if possible let’s try and maintain all the sub-species, but suddenly if we’re saying that the six – now – species of tiger are also in the same category as the snow leopard and the cheetah and the lion, you’ve suddenly increased the amount of funding required for conservation, and in a real sense, does it mean that if we save two species of tiger and lost a cheetah, we’re still okay because we’ve only lost one species?

Interviewer: Shamini Bundell

And is there also a problem with – you know – tigers are pretty cool, we’re probably going to study them in great detail and maybe divide them up more than we would divide up less glamorous animals.

Interviewee: Les Christidis

Oh absolutely, the more something is studied, the more differences you’ll pick up and so you can actually start dividing and defining and calling each one of those things a species. Now, in the past it wasn’t such a big problem but now we have regulations and treaties, so governments then have to change the number of threatened species in their legislation. They need to change legislation so that different forms are covered. You can imagine the amount of legal and legislative changes that are required by a simple taxonomic decision, based on a philosophy.

Interviewer: Shamini Bundell

So this is real world implications for governments and laws and, I guess, individuals and their livelihoods as well.

Interviewee: Les Christidis

Absolutely, and I know that taxonomists love their science and it is a really god and important science but I think they devalue it sometimes by just saying every taxonomist can come up with whatever structure they want and we just let people decide on that. Taxonomists should take responsibility for it and say their decisions have real world implications and maybe some sort of governance and parameters need to be put in to place and taxonomists are the best people to do it. And, yes there’s different viewpoints but the government and the public expect us to do our job properly.

Interviewer: Shamini Bundell

So there’s never going to be a correct answer but let’s at least assign an organisation to make the, sort of, final ruling.

Interviewee: Les Christidis

Well, the International Union of Biological Sciences: that would be our suggestion – a single group that says this is the official listing of mammals, or this is the official listing of birds, and any additions or subtractions are vetted.

Interviewer: Shamini Bundell

Do you think they’ll want to take on this quite mammoth task?

Interviewee: Les Christidis

It would be a courageous decision to take it on but it’s something that needs to be done. There’s two challenges: one is the real one – evolution and we’re trying to pigeon hole a continuum into small single frames at this moment in time which is always going to be difficult. But the other one is the easily solvable one where you’ve got different philosophies – just pick one.

Interviewer: Adam Levy

That was Les Christidis on the phone from New South Wales. The Comment piece that he authored with Stephen T. Garnett is available at nature.com/news.

Interviewer: Kerri Smith

Coming up – one way to make peer review more scientific. That’s after the Research Highlights and this week, a special shout out to our awesome highlights editor and narrator, Corie Lok, who after a decade or so at Nature, in charge of the Research Highlights section, is moving onwards to an awesome new opening.

Interviewer: Corie Lok

Looks like this is going to be my last recording for you guys for the Highlights segment for the podcast. Just wanted to say, thanks for letting me contribute. Here we go.

[Jingle]

Interviewer: Corie Lok

For every particle of matter, there’s a corresponding anti-matter particle. Electrons are constantly running into their antimatter counterparts called positrons, but how the positrons are generated has been a mystery. Researchers now say that most of the antimatter in the space between stars could be created in the explosions of white dwarfs which are the inert remnants of sun-like stars. According to the researchers’ calculations, when white dwarfs between 3 and 6 billion years old merge, the resulting supernovae can generate radioactive titanium 44 which then emits positrons at the observed rate. You can find out more from the journal Nature Astronomy.

[Jingle]

Interviewer: Corie Lok

Blue whales are the biggest animals on earth. How do they and other baleen whales get so big? Researchers used a model to study the evolution of the mammals using data on body length for living and extinct whales. They found that baleen whales that are more than 10 metres long diversified about 3 million years ago. This was a time when shifting winds started to draw colder water, brimming with prey, up from the deep ocean. Larger whales were probably more efficient at moving between and feeding on isolated patches of food than their smaller counterparts. Find the study in theProceedings of the Royal society.

Interviewer: Adam Levy

The wonderful Corie Lok there. Thanks again Corie. We will miss you. You can find the highlights each week at nature.com/news.

Interviewer: Kerri Smith

Sending off your paper for peer review [sound effect]may spark off a conflicting set of emotions. On the one hand your precious manuscript is now in the hands of trusted experts [sigh] deemed the best minds in the land to pick over your work and offer constructive, objective comment [applause]. On the other hand, they are human. What if your reviewers read your paper and think…

Interviewer: Jayshan Carpen

Huh, I just don’t get it…

Interviewer: Kerri Smith

Or worse…

Interviewer: Jayshan Carpen

Eurgh, a paper from my competitor.

Interviewer: Kerri Smith

After all, these decisions can shape careers. Scientists have been arguing about peer review ever since there’s been peer review and there’s been peer review in some form for a couple of hundred years. Usually it’s just a handful of scientists – you ask for their opinion. But how would you feel if this handful became a crowd and a hundred people were asked to pick over your work? Would that be an order of magnitude messier? Quite the opposite according to Benjamin List. He’s the Editor-in-Chief of a Chemistry journal called SYNLETT and he made his case for intelligent crowd reviewing to reporter Geoff Marsh.

Interviewer: Geoff Marsh

What do you see as the problem then with the current peer review system?

Interviewee: Benjamin Lister

First of all, often peer-reviewing just takes a long time. Often, our referees also are busy. They are just travelling the world and they do other things and then once it comes to somebody refereeing it, he might be biased or he makes mistakes. It’s weird if you think about it; in order to be published we have this weak bottle neck where just less than a handful of people propose their personal opinions. It’s totally not a scientific method, I would say, in how we handle scientific manuscripts.

Interviewer: Geoff Marsh

So let’s hear then about your new proposition which you’ve called intelligent crowd reviewing.

Interviewee: Benjamin Lister

Our idea is not that we just put it online and everyone can comment on a manuscript but we have a selected group of referees and it’s a larger number, a much larger number, than the 2 to 4 referees that is normally used. When you have a biased referee now, this will immediately be corrected. Imagine you have a hundred referees – one referee is your buddy and he writes, ‘this is an outstanding manuscript – the authors should win the Nobel Prize,’ then there are 99 other people who are much more objective and they say, ‘wait a minute there’s a few mistakes here,’ and so on. There’s just something – as far as I know, which has not been really utilised in the past, at least in a convenient fashion.

Interviewer: Geoff Marsh

Now, as a scientist, Benjamin, obviously you’re not expecting us all to just take your word on this system. You set up a framework – or actually your undergraduate student, Denis Höfler, set up a lot of this framework to actually test your theory and I believe he joins us now.

Interviewee: Denis Höfler

Hello Geoff.

Interviewer: Geoff Marsh

Let’s briefly talk numbers then. Traditional peer reviews: somewhere between 2 and 4 expert referees. How many did you recruit, then, to constitute your intelligent crowd?

Interviewee: Denis Höfler

Our first test, we started with around 60 and these scientists were of very diverse backgrounds, so we had postdocs, student professors, PhD students, people who we can trust.

Interviewer: Geoff Marsh

How did they interact with the manuscript?

Interviewee: Denis Höfler

So, in the centre of the platform we uploaded a manuscript and they were actually able to highlight parts of the manuscript of which they could comment on and everybody in the crowd is then able to see which parts have been commented on and everything is happening completely anonymously so people can actually be quite frank with each other.

Interviewer: Geoff Marsh

How did you test the relative merits of this system versus the old?

Interviewee: Denis Höfler

So we took 10 manuscripts. All of them were traditionally peer reviewed – so by selecting 2 to 4 people. In parallel, with the consent of the authors we did our crowd reviewing experiments.

Interviewer: Geoff Marsh

And so, back to Benjamin. First of all, what did the authors think of this new process?

Interviewee: Benjamin Lister

They were all delighted at how fast the refereeing process went but also about the quality. In the majority of these cases which were ultimately accepted, the authors could massively improve on the original submission.

Interviewer: Geoff Marsh

But isn’t it a fair concern that perhaps authors might be a bit worried about sending out unpublished, exciting, new findings to maybe a hundred anonymous fellow scientists?

Interviewee: Benjamin Lister

You should be aware though that this of course is always a problem with any type of peer reviewing.

Interviewer: Geoff Marsh

But it definitely sort of amplifies that risk a bit doesn’t it?

Interviewee: Benjamin Lister

Yeah, it amplifies it and that’s of course, in principle, a problem but if we ever have one person misbehaving in the slightest way, he’s out of the crowd. The other aspect I’d like to point out is that the refereeing process is so fast that it’s done in two days. Nobody can take your idea and then quickly do it in his lab and publish a paper independently.

Interviewer: Geoff Marsh

What about the work load then on peer reviewers because that’s what we started off by saying. It is an unpaid, potentially laborious job. Now if they’re part of this crowd, presumably that means they get called upon much more often?

Interviewee: Benjamin Lister

This is indeed the case, however, and here come a very important point; you only comment when you’re inclined to comment. All the burden that rests on your shoulders, that you are responsible now if this work gets published or not, is shared by a hundred other people.

Interviewer: Geoff Marsh

Okay, and if anyone were doubting your commitment to this new system, I should point out that your journals are now transitioning over to a fully intelligent crowd based reviewing system.

Interviewee: Benjamin Lister

That’s the plan at least. We are not yet there, but this is happening right now and I would expect maybe by the end of this year, or let’s say in one year, we’re all using crowd reviewing.

Interviewer: Geoff Marsh

When you say ‘we’re all’, are you talking about…

Interviewee: Benjamin Lister

My associate editors and I.

Interviewer: Geoff Marsh

The whole world will be…

Interviewee: Benjamin Lister

No, no.

Interviewer: Geoff Marsh

Well – but on that point, what do you expect for this new system?

Interviewee: Benjamin Lister

Well, the bottom line is, in our experiments we found it simply works and it works really, really well. It’s much faster than traditional peer reviewing but the quality doesn’t suffer at the same time so we get more information. And I think there’s great potential, not only for synthetic chemistry, but, you know, why not in other fields?

Interviewer: Kerri Smith

That was Benjamin List joined by his student and editorial assistant at SYNLETT, Denis Höfler. They were speaking to Geoff Marsh. Well, intelligent peers, what’s your judgement on Benjamin’s proposal? Maybe you work in a controversial field where a hundred experts would implode the internet if they were all given a say, or maybe you work in a field where there aren’t even a hundred experts to ask. We’d like to know the Nature Podcast’scrowd’s thoughts on the matter so let us know on Twitter. We are @naturepodcast.

Interviewer: Adam Levy

Time now for this week’s News Chat and Lizzie Gibney has popped down to the studio. Hi Lizzie.

Interviewee: Lizzie Gibney

Hi Adam.

Interviewer: Adam Levy

Now, one of my favourite things on my news feed this week were some pictures of Jupiter that have been taken quite recently, right?

Interviewee: Lizzie Gibney

Yes, so this is NASA’s Juno Spacecraft. So, it arrived there last year and it’s been doing these elliptical orbits and finding out some fascinating things about Jupiter.

Interviewer: Adam Levy

I think we maybe discussed on Backchat once that space missions are the perfect diversions from some of the things that are happening on this world and these pictures are a perfect example of that but presumably they’re not just beautiful little baubles to distract us from what’s going on here.

Interviewee: Lizzie Gibney

That’s very true and actually what’s interesting is that a lot of the most interesting findings are not about these swirling clouds that we see on the surface but the very fact that Juno can see beneath the clouds. It uses a microbe instrument so we’re actually finding out what’s going on beneath the clouds and then even what the core of the planet seems to be like.

Interviewer: Adam Levy

Are there any surprises so far or is it kind of just confirming how we thought Jupiter was?

Interviewee: Lizzie Gibney

It seems like every mission like this – you go there and actually it’s bigger, crazier, weirder than you thought. Yeah, so we found that instead of ammonia being diffused throughout the atmosphere, there’s actually only a little bit of ammonia in most places, but then these big plumes that are coming out around the equator. We also found out about its magnetic field. It has a very powerful magnetic field and that it’s a lot patchier than people thought which may suggest that something is going on inside the planet, some kind of churning and then something else which was a little strange to do with a magnetic field is the way that it manifests itself at the poles, so where it stream out of the planet, instead of streaming out in even streams, it’s like having lots of different wires sticking out which would make for a really beautiful aurora I think. The northern and southern lights on Jupiter would be pretty spectacular.

Interviewer: Adam Levy

Quite difficult to see them, I suppose.

Interviewee: Lizzie Gibney

Yeah, I’m not sure we’re ever going to be able to see them. It might have to remain in people’s imaginations.

Interviewer: Adam Levy

Now, this definitely isn’t it for Juno, right? It’s been there a little while but there’s still some way to go?

Interviewee: Lizzie Gibney

Absolutely, these are just the preliminary findings. So this is the very first few bits and bobs that we’ve been able to put together.

Interviewer: Adam Levy

And how long is it going to be sticking around?

Interviewee: Lizzie Gibney

Juno’s going to be staying around Jupiter until next year. I’m not sure of the exact date but it’s going to then burn up in the atmosphere to make sure that the spacecraft doesn’t contaminate Europa which is one of the moons of Jupiter and where there is a tiny chance that even life may exist.

Interviewer: Adam Levy

Is it taking any measurements on its way into Jupiter?

Interviewee: Lizzie Gibney

Absolutely, so at the moment it’s doing these elliptical sweeps around and then when it comes to the end of its life, the craft will also be monitoring the atmosphere as it dives into it so we’ll get some good close ups then as well.

Interviewer: Adam Levy

Let’s move on to our second story which is, unusually, something even bigger than Jupiter. It’s regarding neutron stars.

Interviewee: Lizzie Gibney

Well it’s certainly more massive.

Interviewer: Adam Levy

Oh but bigger…

Interviewee: Lizzie Gibney

It’s certainly a lot smaller than Jupiter, so…

Interviewer: Adam Levy

Okay. I stand corrected.

Interviewee: Lizzie Gibney

So neutron stars are just… they just blow your mind in terms of trying to imagine them. So they are smaller than a city. They’re about 10 or 12 kilometres in radius but they’ve got more mass than the sun so it’s just a phenomenal amount of matter crammed into a tiny space. They’re on that border, on that threshold before becoming – you know – any more massive and they’d be a black hole, but they not quite. Matter is still holding it together at this point.

Interviewer: Adam Levy

And now there are efforts to actually see what’s going on inside a neutron star?

Interviewee: Lizzie Gibney

Exactly. So the thing with this kind of matter is we can’t – we have no chance of creating it on earth so you can try and have very, very high-pressure, high-density environments when you collide particles but that’s so short lived and it’s also very, very hot. Whereas inside one of these stars it’s actually very stable and relatively cool. So we just have no way of knowing what’s happening in their core unless we try and do these measurements. So this is a mission called NICER, another NASA mission. It’s a relatively cheap one as well at a mere 55 million dollars.

Interviewer: Adam Levy

A bargain.

Interviewee: Lizzie Gibney

Absolutely. For what we’re getting out of it, it probably will be. And what it’s going to be able to do is measure both the mass to radius ratio of the stars and also through separate means, measure the mass, and in that way you can tell between lots of the different possible theories about how matter might be arranged within the neutron star’s core.

Interviewer: Adam Levy

How different are these theories from each other?

Interviewee: Lizzie Gibney

They’re pretty different. So, on one end of the scale you’ve got the idea that actually by the time you get down to the core you still have neutrons as we know them, so they’re made up of quarks but they’re all combined in set particles. You can imagine them like marbles and you might have a few protons as well and they’d just be packed together but packed in with a pressure much higher than within atomic nuclei so it would be like one giant atomic nucleus in fact. So that would create quite a stiff core that will be able to withstand the huge force of gravity pushing in on it. And then you’ve also got the idea that perhaps, rather than being confined still in these particles, the neutrons break down into their constituent quarks and then you’ve got a kind of soup and it would be probably smaller and softer and you’d be able to tell the difference between those by knowing what this mass to radius ratio is.

Interviewer: Adam Levy

How is it measuring this mass to radius ratio in the first place?

Interviewee: Lizzie Gibney

So we’re looking at pulsars in particular – that’s a type of neutron star that has these – you can imagine it like a lighthouse beam that sweeps past earth and some of these, they rotate at different speeds but it can be hundreds or thousands of times every second. When they do that – because the star has such an enormous gravitational field – some of that light will get bent back, so even when this beam is facing away from us, some of it will come back to earth. So the fluctuation in how the light changes as it sweeps past us, tells us about that gravitational field around the star. And from that combined with – it’s actually doing a huge number of different bits of information – it’s trying to glean from this light spectrum, but from all of those together we can figure out what this ratio is.

Interviewer: Adam Levy

But in terms of how it actually watches and measures this light: how are we doing it and why couldn’t we do that before?

Interviewee: Lizzie Gibney

So this is a little observatory that’ll go on the International Space Station and it’s launching on the 1stJune. It’s not looking at the light with any great resolution in terms of space but it has incredible time resolution, so it can detect the arrival time of each photon with an accuracy of about 100 nano-seconds, so it’s an incredible piece of timing equipment.

Interviewer: Adam Levy

It’s an amazing experiment. It never occurred to me that you’d look inside a neutron star.

Interviewee: Lizzie Gibney

Exactly and what is pretty cool is the fact that we’re learning about what’s happening right in the centre, just by the fact that by knowing these seemingly quite simple measurements, that allows us to tell the difference between these quite wildly different theories about what’s going on at the actual level of neutrons and even quarks.

Interviewer: Adam Levy

Thank you, Lizzie. Learn more about neutron stars at nature.com/news where you’ll also find the piece and pictures of Jupiter.

Interviewer: Kerri Smith

That’s all we have time for this week. In the meantime, a new sci-fi short just landed and you can find it on the podcast feed and on our website, nature.com/nature/podcast right now. I’m Kerri Smith.

Interviewer: Adam Levy

And I’m Adam Levy.

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