Astronomers Spy A Two-Faced Star

11:52 minutes

an illustration of w light blue sphere, which is a white dwarf star, in space
An artist’s concept of the two-faced white dwarf, nicknamed Janus. Credit: K. Miller, Caltech/IPAC

This week, astronomers report in the journal Nature that they’ve discovered a white dwarf—a dying star’s dense inner core—that, instead of being uniform in composition, has a surface that appears to be hydrogen on one face and helium on the other. The star rotates on its axis once every 15 minutes, bringing each face into view.  Researchers spotted the unusual object with an instrument called the Zwicky Transient Facility, which initially singled out the star because of its rapidly changing brightness.  

The astronomers aren’t sure why the white dwarf, which they’ve nicknamed Janus after the two-faced Roman god, has this strange divided surface. Some possible theories include shifting magnetic fields which produce areas of different density, or that it’s a step in stellar evolution only partially complete. 

Tim Revell, deputy US editor at New Scientist, joins John Dankosky to talk about the two-faced star and other stories from the week in science, including the resignation of the Stanford University president amidst an ethics probe, discovery of ancient natural graphene, an earthworm invasion in the Arctic, and investigations of alcoholic fruit.

Segment Guests

Tim Revell

Tim Revell is Executive Editor at New Scientist in London, England.

Segment Transcript

JOHN DANKOSKY: This is Science Friday. I’m John Dankosky in for Ira Flatow today. A bit later this hour, we’re going to talk about how the brain controls movement and what that means for neuroscience as a whole. But first, imagine a globe that if you looked at it from one side, it was all land, and when you spun it around, it was all water. This week, astronomers report in the journal Nature that they’ve spotted a white dwarf. That’s the dense inner core of a dying star. That’s the stellar equivalent of that globe.

This star has a surface that appears to be all hydrogen on one face, all helium on the other. Hmm. Joining me to talk about that and some other short subjects in science is Timothy Revell. He’s Deputy US Editor at New Scientist and he’s right here in our New York Studios. Welcome back to the show, Tim. It’s good to see you.

TIMOTHY REVEL: It’s great to see you, too.

JOHN DANKOSKY: OK. So first of all, I guess, tell us more about this star, this weird star.

TIMOTHY REVELL: Yeah. It’s absolutely amazing. So it was spotted about 1,300 light years away from Earth and it rotates about once every 15 minutes, and that means we get to see its two different sides a lot.


And so there were researchers at the Zwicky Transient Facility in California. They were looking at the sky, just a standard observation of the sky, and then they suddenly spotted this very strange looking star. And as you say, on one side, it’s completely helium, and on the other side, completely hydrogen.

JOHN DANKOSKY: So they found this just on a random sky scan, but I assume that they’ve confirmed this with some other fancy instruments by now.

TIMOTHY REVELL: Yeah, exactly. So they confirmed it with other telescopes and they confirmed it using spectrometry, which is a sort of chemical fingerprint of the star, and that allowed them to see what chemicals were mostly composed on the surface.

JOHN DANKOSKY: OK. So they can see it. They can understand basically what it is. But do they know why this has happened?

TIMOTHY REVELL: Yeah, we don’t know why it’s happened. We know that, with white dwarfs, they can transition from being mostly helium to mostly hydrogen on the surface and that happens at a fairly regular occurrence. And so maybe we’ve just caught it in the middle. We’ve caught it in a slightly strange moment.

But what the astronomers who spotted this reckon, instead, is that maybe that the magnetic field has slightly gone off kilter and it’s a bit stronger on one side than the other. And what would happen is that would mess with the internal convection inside the star, the sort of churning that happens of the gases, and then maybe that means that you end up with more helium on one side and more hydrogen on the other.

JOHN DANKOSKY: That’s so interesting. Of course, there’s so many space observers and space-interested folks in our listening audience. I’m sure that they’re going to ask, can I look at it myself?

TIMOTHY REVELL: I think it’s going to be very difficult for you to see it yourself, unless you have an amazing telescope. But if you could see it, if you were right there and you could have a look at it, something that you would see is that it would be bluish, and then the helium side would look a little grainy and the hydrogen side would be very smooth.

JOHN DANKOSKY: Ah. And do they think that there’s any more of these things out there?

TIMOTHY REVELL: We don’t know. This is the first one we’ve ever spotted. That’s what’s so amazing about it. We’ve never seen a two-faced star like this before. But now we know what it looks like. Potentially, we can scan the skies for a few more, and maybe there’s more out there. But certainly it seems rare.

JOHN DANKOSKY: That’s very, very cool. OK, so let’s go to another story about chemical elements. The form of carbon known as graphene, why don’t you tell me about this first?

TIMOTHY REVELL: Yeah. This discovery absolutely blew my mind. So you might remember in 2004 that, humans, we created graphene, which is this sort of wonder material that’s a single layer of carbon. It’s one atom thick and it’s meant to be incredibly strong, 100 times stronger than steel, and it has amazing electroconductivity.

But when we found it, we thought, well, we’ve just invented this now. This is an amazing new material. But what–

JOHN DANKOSKY: Go, humans!

TIMOTHY REVELL: Yeah. Go, humans! But now it seems like nature has gone into the lead. It turns out nature discovered graphene at least 3.2 billion years ago, and we’ve only just found that out now.

JOHN DANKOSKY: Interesting. OK. So first of all, how exactly did they find this out?

TIMOTHY REVELL: Yeah. So researchers were just looking in this gold mine in South Africa, and under some rocks was a sort of interesting-looking material. They took it back to the lab and looked at it under a microscope, and they were pretty shocked to find out that graphene, this amazing material, there it was in this mine.

JOHN DANKOSKY: So we now have learned how to make graphene ourselves. I don’t know. Does it get us anything fancy because we’re able to get it in nature now?

TIMOTHY REVELL: Yeah. so this is what’s particularly interesting about the discovery, other than just the scientific wonder of it, is that graphene was originally discovered with some graphite from a graphite from a pencil and some sticky tape, a really basic way of making it. Because it’s such an amazing material, we want to be able to make it in vast quantities, and the industrial processes for making them use extremely high temperatures, up to about 1800 degrees Fahrenheit.

And with this naturally-occurring graphite, graphene, sorry, it seems that it occurred from a combination of bacteria, dying, and then undergoing some chemical reactions, but these chemical reactions occur only at about 500 degrees Fahrenheit. So much, much cooler. So maybe we’ll find a much more energy-efficient way to make this amazing material off the back of it.

JOHN DANKOSKY: But it was found in a gold mine. Is this something that you can mine for?

TIMOTHY REVELL: Yeah, potentially. It’s like such early stages at this point that they’ve just– They’ve got a few little samples. They’ve got some graphene there. The graphene seems to be slightly different to the graphene that we have created in the lab. It’s a slightly different color, so maybe it’s got some other elements in it. But yeah, I think most likely is that it will inform how we can make it on an industrial scale. But mining is certainly not ruled out at this point.

JOHN DANKOSKY: Very interesting. OK, so later this hour, we’re going to be talking about the brain and how it directs the movement of our body. But there’s some other brain news this week, and it’s about consciousness and what exactly it might be in the brain. What can you tell us? This is a big idea.

TIMOTHY REVELL: Yeah, it’s a really big idea. And so any progress on this, even if it’s small, seems like big progress. And what we have now is a stronger evidence for one of the explanations potentially for how consciousness arises in the brain. And so there are many competing ideas about consciousness and how it arises, but one of them is called IIT, and that stands for Integrated information theory.

It’s a pretty technical and very maths-heavy theory, but one of the things it says is that when two things interact, if that produces more information than there was at the beginning of the interaction, that is consciousness. That is like the beginnings of consciousness. And so researchers have now tested this theory to see whether it does work in the way that IIT predicts.

And what they did was they looked at brain scans from 17 people in four different states of consciousness. There was awake, mildly sedated, unconscious, and in a recovery state from an anesthetic. And what they found was this sort of calculation that you can do in IIT, which produces a number called phi. They found that it relates to consciousness in the way that you would expect. So higher consciousness increases with phi, and then consciousness also decreases when you’ve got a lower number.

JOHN DANKOSKY: When you’re talking about that, the first thing I think about is it seems like a fairly, in some ways, simple formulation that could apply to animal consciousness. It could apply to machine consciousness, I suppose.

TIMOTHY REVELL: Yeah, this is the thing about the theory is that it only tells you about these interactions between two things, and then maybe you can build them up to a higher level. But the brain consists of billions of neurons, and the mathematics is so complicated that we can really only perform the calculations, at the moment, for a few components. And so what they did in this study was they worked out a way in which you can simplify the brain to look at regions rather than the neurons itself, and that matched the theory.

But it’s so complicated that it’s really just like a bit of inching forward. Potentially, this is the strongest theory we have for consciousness, but it’s a long way yet before it will be proven.

JOHN DANKOSKY: Yeah, I was going to say, it’s a long way before it can be proven. This is something we’ve been thinking about as humans for quite some time. So the debate is not settled here?

TIMOTHY REVELL: No, it’s not settled. There are other people who think there are other stronger theories, but this is some new evidence that we didn’t have before.

JOHN DANKOSKY: So there’s some news this week out of Stanford University, really interesting news, that the Stanford University President has had to resign, following an ethics probe and it’s a science ethics probe. Tell us what’s going on here.

TIMOTHY REVELL: Yeah, so Stanford President is Marc Tessier-Lavigne, and he’s a pretty notable neuroscientist who’s published more than 200 papers on degenerative brain disease. But he said he’s now going to resign after an independent report concluded his research contained, and this is a quote, multiple problems and fell below customary standards of scientific rigor.

And so the report it looked at, it took in 50 interviews and had over 50,000 documents as part of the report, and they said that the Stanford president’s labs had inappropriately manipulated research data, and in several instances, he himself hadn’t taken proper steps to correct mistakes.

JOHN DANKOSKY: My goodness, this is quite a story, which we’ll continue to follow. Let’s go to some animal news, Tim. Two new species of saber-toothed cats have been discovered. This is interesting.

TIMOTHY REVELL: Yeah, this is amazing. So saber-toothed cats, they roamed the Earth from about 56 million years ago to about 10,000 years ago. And we already know that there were about two dozen species that we know of. And so researchers are still trying to work out exactly which saber-toothed species lived where and when. And so a team reexamined a large collection of fossils from near Cape Town in South Africa.

And those fossils actually were originally unearthed 40 decades ago, but they’ve just had another look at them– Uh, four decades ago, and they’ve just had another look at them. And from the team’s analysis, they were able to identify two medium-sized saber-toothed species that were different from any of the others that we know of.

JOHN DANKOSKY: Interesting. OK. So this is a really important thing.

TIMOTHY REVELL: Yeah, it’s a really important thing. And, like, we know a little bit about from this analysis what the saber-toothed cats would have been like. So one of the species we could tell from the sort of shape of its skull that it was probably a bit like a leopard and hunted prey in the forests, whereas the other one was much more of a runner and it sort of hunted like a cheetah, which is an absolutely terrifying prospect, a cheetah with saber-toothed fangs coming at you.

JOHN DANKOSKY: I can’t even imagine. It actually stirs the imagination a bit. OK. Before we run out of time, we’re heading into the weekend here. And if you’ve been considering a fruity drink of some sort, you’ve brought us a story about alcohol and tropical fruits. OK, tell us about this.

TIMOTHY REVELL: Yeah, this is great. So plants in tropical forests, they seem to have a pretty cunning technique for luring mammals to eat their fruits and distribute their seeds, and it’s a technique that often works for humans, too. And it’s alcohol. So it seems that there was these researchers and they collected a wide range of fruits from a Costa Rican tropical forest, and then they sampled the alcohol content of all these different fruits. They found 80% of them had some noticeable alcohol in them.

But then when they looked at which animals ate which fruits, they found that those with higher levels of alcohol were much more likely to be eaten by mammals.


JOHN DANKOSKY: So in some ways, that’s not surprising, right?

TIMOTHY REVELL: Yeah. so the alcohol, it comes from natural yeast turning the sugars into alcohol. And so the fruits in which that happens most are the ones that are ripest, the ones that have the most sugar, and ultimately the ones that have the most nutrition. So maybe that’s what enticing the animals. Though it could be the taste of alcohol.

JOHN DANKOSKY: It could be the taste. I mean, how much alcohol are we talking about? Are we talking about little tipsy monkeys in the jungle here?

TIMOTHY REVELL: We’re talking about a very low amount of alcohol. So the highest concentration of alcohol in any of these fruits was in the hog plum, which I’ve never tasted before, but I would be up for trying, and that one had 1.5% alcohol. And most of them were much lower. So I think only very small animals that eat a lot of fruit would really be noticing the intoxicating effects.

JOHN DANKOSKY: You’ve never had hog plum brandy? It’s such a delicacy.

TIMOTHY REVELL: Well, I must have it with you sometime.

JOHN DANKOSKY: Thanks for bringing us all these stories, Tim. I really appreciate it.

TIMOTHY REVELL: Thanks for having me.

JOHN DANKOSKY: Tim Revell is Deputy US Editor at New Scientist.

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