Cosmic Colour: The Discovery of the Universe's First Ghostly Green Star

0:00Stuart Gary This is space time series 29 episode

0:02 126 for broadcast on 21st October 2026. Coming up on Space, discovery of the first star in the universe that glows a ghostly green. A ah, major upgrade for gravitational wave detection and a new era of nuclear powered space exploration on its way. All that and more coming up on, um, Space Time. Welcome to Space Time with Stuart G.

0:46 Astronomers have discovered the first star in the universe that glows a ghostly green. The star is a white dwarf catalogued as WD J 13306435 and located some 284 light years away. White dwarfs are the exposed whiteout stellar cores of sun like stars at the ends of their lives. These new observations reported in the Journal of the Royal Astronomical Society show that white dwarfs actually glow in a remarkably wide range of colours. For astronomers studying stars, colour is a guide to temperature. Cooler stars look red or orange, while stars like our uh, sun are yellow and the hotter stars glow white or blue. It was always thought white dwarfs follow the same rule. In fact they earned their name because the earliest examples were

1:31 found to be surprisingly hot and they glowed a white, pale blue. But according to the studies lead author uh, Mark Hollins from the University of Warwick, if astronomers could actually view them up close, some white dwarfs would shine in a variety of different colours, including green, pink, cyan, yellow and purple.

1:49 He says most stars, including most white dwarves, behave like perfect blackbody radiators. So their colour is set almost entirely by temperature. But it turns out these incredibly dense white dwarf stars can produce colours nobody ever expected. By the way, a perfect blackbody radiator, well that's an idealised object that absorbs all the electromagnetic radiation that hits it.

2:10 There is no reflection, no transmission and so black bodies only emit the maximum possible thermal radiation for their temperature. Holland says the key to a white dwarf's real colour is density. The coolest white dwarf atmospheres can reach around 1 gramme per cubic centimetre, roughly the density of water and millions of times denser than the the sun's photosphere. In these conditions, any trace elements that may be present, such as carbon, calcium and sodium, interact with the surrounding dense helium plasma, absorbing light across a wider range of colours than what they would at lower densities. And so this shifts the star's true colour away from the usual whitish appearance. The authors calculated

2:50 the true colour of a group of white dwarves by running their stellar spectra through a model of human colour vision in order to reveal what colour each star's light would appear to the average unaided eye. And Hollins and colleagues found their colours fall into distinct groups, each linked to what's in the star's atmosphere. Carbon rich white dwarfs are typically pink or purple in colour, while those enriched with debris from scattered asteroids or comets or the remains of old planetary systems tend more towards yellow. Cooler white dwarfs with mixed hydrogen and helium atmospheres often take on a cyan or pale blue tinge that's caused by hydrogen molecules colliding with helium atoms in their ultra dense atmospheres. But

3:29 the authors found the most striking example was a star called WDJ 1336435, which has a surface temperature of roughly 4,000 degrees Celsius and has accreted rocky material from its planetary system. This has enriched its atmosphere with calcium, lithium and sodium, giving it a chartreuse green appearance. In the author's models, the traces of sodium in the atmosphere of this white dwarf absorb the orange part of the spectrum, leaving behind the ghostly green glow. At the opposite extreme, Hollins and colleagues identified what may be the reddest star ever recorded. WD J1011 2845, a nearby white dwarf just 48 light years away, has a deep convection zone that's lifted carbon from its core up to its surface. The

4:14 resulting carbon molecules distort the star's light so heavily that almost all of it squeezed into wavelengths beyond 600 nanometers, producing a deep salmon pink glow unlike anything seen in an ordinary star. The authors also studied a representative sample. Some 151 white dwarves within 65 light years of the earth. Uh, five showed unusual colourings.

4:36 Two yellow, three pink. This suggests that roughly one in 30 white dwarfs will shine with an unusually coloured light. As for the remaining 146, well, the authors measured the colour temperature, finding them to really do appear, ah, to be white. This is space time still to come, a major upgrade for gravitational wave detection and a new era of nuclear powered space exploration on its way. All that and more still to come on, uh, space time.

5:13 The Laser Interferometer Gravitational Wave Observatory LIGO is undergoing a major upgrade with the application of a new Australian developed optical coating for the beam splitters first predicted by Albert Einstein back in 1916 as a consequence of his general theory of relativity. Gravitational waves are ripples through the fabric of spacetime caused by the movement of massive objects such as the collision of black holes or neutron stars. The LIGO Observatory comprises two identical facilities, one in Livingston, Louisiana, the other at Hanford in Washington State. Each LIGO observatory fires precision lasers into A beam splitter, uh, which then shoots the beams along two perpendicular four kilometre

5:54 long tubes equipped with mirrored test masses at each end. The reflected laser light is then sent back to the detector, uh, where eventually they should theoretically recombine. As a gravity wave passes through the cosmos, it causes the fabric of space time to stretch and compress ever so slightly by just a fraction of the diameter of a proton, less than a millionth of a billionth of the diameter of a human hair. When a gravitational wave passes through the LIGO detector, local space time, including the two beamlines and the test masses are also stretched and compressed ever so slightly, slightly leaving them out of phase. And that's the signature of a gravitational wave event. Using multiple gravitational wave

6:34 detectors allows scientists to determine the direction of the wave source. The addition of the third detector, called Virgo, located near Pisa in northern Italy, and Japan's Kamioka detector have further improved detection. Each beam Splitter is a 45 centimetre disc made from the purest glass ever produced. Weighing around 20 kilogrammes, the coating on one side splits the pure laser beam light precisely in half.

7:00 On the other, an ultra low reflectivity coating, over a thousand times more effective than an ordinary eyeglass lens coating, minimises interference and improves detector sensitivity. One of the researchers behind the development of the new optical coatings, Professor Steve Madden from the Australian National University, says it will allow scientists to detect gravitational waves with greater sensitivity than ever before. He says these are some of the most exciting and precise coatings ever made. In fact, Madden and colleagues spent more than three years researching and developing the nanometer thin coatings, which are just a few atoms thick and uh, which have driven precision optics to unprecedented levels. They are one of only

7:39 two groups in the world capable of producing these coatings to the exacting standards required for gravitational wave detection. To achieve this, the team developed eight custom automated systems to clean, measure and handle the delicate components without any human contact. Madden says the upgraded detectors will pick up more gravitational wave events, including weaker signals from further away, allowing astronomers to study the behaviour of some of the universe's most mysterious objects in far greater detail than ever before.

8:08Alex Zaharov-Reutt LIGO is probably the most sensitive

8:11 distance measurement ever made on Earth, where basically we're looking for the distortion that the gravitational waves from merges of black holes, for example, when they merge together they create a massive disturbance in spacetime, propagates out through the universe and that disturbance manifests on Earth, uh, as a slight distortion in distances very, very tiny amounts we're talking about here like 10 to the minus 24 metres. And so LIGO is a laser interferometer device designed to detect those very tiny changes in distance. But to do so it needs some really, really complex technology and really high performance components. And in any interferometer, we're basically taking a laser beam, dividing it into half, sending

8:59 each half down a separate path and then recombining them and picking up any difference in the two path lengths that we just came back through. So the beam split is a really key component here. And as it first of all splits the light very, uh, very equally, which enhances the level of signal that we get back the more equal those, those two powers in each, um, arm are. And then it also provides the function of recombining them so that we can detect the difference in the two arms. So the beam splitter has two sides. One splits the laser equally and the other side has to be coated with an anti reflection coating like we have on our spectacle lenses. Except this coating is like a thousand times better

9:40 because any stray reflections inside the beam splitter degrade the signal very significantly. So that anti reflection coating has to be basically almost perfect.

9:49Stuart Gary Tell me about the coating. What's it made out

9:51 of?

9:51Alex Zaharov-Reutt Well, the coatings made out of a sequence of

9:54 different layers of silica. So silicon dioxide, like sand on the beach, just much, much purer. And something called tantalum pentoxide, which is an oxide of the metal tantalum.

10:05Stuart Gary I take it you just don't slap it on. It's got

10:07 to be applied in a special way?

10:08Alex Zaharov-Reutt Oh, yes. The application is

10:11 done in a very large vacuum system. And, uh, basically we use a process called ion beam sputtering. And what happens here is that we have a gun that has a discharge plasma of oxygen and argon inside and there is various grids, uh, in there that extract the charged ions out and accelerate them to about 1200 volts and then neutralise. So we have, uh, instead of an actual. The name's a bit of a misnomer.

10:37 It's not actually an ion beam, it's a neutral beam, but it's formed via an ion process. So you've got these energetic oxygen and argon atoms flying at quite high velocity towards a large target material. And the target materials are either silicon dioxide or a metallic tantalum target. And they impact the surface and they knock atoms off that target. And those atoms then are also oxidised by the presence of oxygen in the vacuum. And those particles themselves because they've sort of been knocked off by something else moving at high velocity. If you like, they have a rebound velocity of their own, so they fly away from the target and then deposit onto the substrate that we're going to coat.

11:19Stuart Gary So you're literally adding atom by atom,

11:21 essentially.

11:22Alex Zaharov-Reutt Yes. And um, the name of the game,

11:24 particularly with ligo, the substrates that we're using, some of the purest glass ever made and they're uh, about half a metre in diameter. And the big challenge here is to get the uniformity over something of that size and to get the precision of the thickness of the individual layers. So we're talking about trying to achieve uniformity to a few atomic layers across the entire substrate and to target similar levels of accuracy in the thickness of each layer. So it's actually really, really hard to do that.

11:54Stuart Gary And this will replace the existing, uh, beam

11:57 splitter coatings. Do you replace the whole beam splitter or what happens now?

12:01Alex Zaharov-Reutt The whole beam splitter is replaced. They

12:03 wanted to have bigger beam splitters in there because they want to be able to move the beams around inside the um, whole system. And the existing beam splitters didn't really have very much real estate for this so uh, they had to go to new larger and these literally called the big beam splitters.

12:19Stuart Gary And this will let us see even finer

12:21 details in terms of the movement of the fabric of space time itself. Wow.

12:25Alex Zaharov-Reutt Uh, yep, Finer and further away,

12:28 there's about a factor of two improvement in the seeing distance.

12:31Stuart Gary I think that's Professor Steve Madden from

12:33 the Australian National University. And this is space time still to come. A new era of nuclear powered space exploration on its way. Later in the science report, Boeing awarded the contract to build the US Navy's new FAX Multi Role fighter aircraft. All that and more still to calm down on space time, NASA's Artemis programme, designed to return people to the moon and eventually onto Mars and beyond, has now moved a step closer to a nuclear powered future. NASA and the United States Department of Energy have just signed a new memorandum of understanding to develop next generation nuclear technologies for space. NASA Administrator Jared Isaacman says the research will see the beginning of a major transformation for space

13:33 exploration, allowing spacecraft to go further, operate longer and field more capabilities than ever before. He says the work will lay down the foundation for nuclear fission powered spacecraft and cover the full spectrum of space nuclear development, spanning advanced research, fuel production, testing, launch integration and operations. Isaacman says when NASA's Space Reactor One Freedom launches in 2028, nuclear propulsion will advance from laboratory research to operational deep space applications, paving the way for Lunar Reactor 1, the fission surface power system that will sustain NASA's future moon base at the lunar south pole. It means nuclear power will energise habitats, communications

14:15 instruments, rovers, resource usage and other critical lunar infrastructure. And it will be essential for the demanding energy needs for future missions to Mars, potentially even cutting journey times down from six or seven months to just two or three months. It's an exciting future and one coming sooner than you think. This is space time.

14:45Alex Zaharov-Reutt Foreign.

14:52Stuart Gary Look at some of the other stories making news

14:54 insights this week with a science report. New research shows that playing your favourite music really can lessen the amount of pain you suffer during minor medical procedures. The findings, reported in the journal Frontiers of Pain Research, also show that playing your preferred playlist was better for reducing pain than playing other music specifically designed for relaxation, the study found that people who were listening to their favourite music experienced less pain both 30 seconds and two minutes after a cannula was inserted, while people listening to relaxation music felt no change in their level of pain. The United States Navy have awarded Boeing a AH $20 billion contract to build its sixth

15:33 generation carrier based jet fighter which will replace the current fleet of F A 18 Super Hornets and EA 18G Growlers. The first of the new Fax stealth fighters will begin entering service in the early 2000 and 30s. Boeing won the contract over Northrop Grumman after Lockheed Martin was eliminated from the competition. These new combat aircraft will have 25% greater range than the current F A18s and be able to operate alongside the Navy's F35C Lightning II joint Strike fighters which are not optimised for long range strike capabilities. They will also be capable of controlling at least four unmanned loyal wingman semi autonomous drones at a time.

16:13 For Boeing, it's a real coup. They've already won the contract to build the US Air Force's F47 sixth generation air dominant Stealth fighter which will replace the existing F22 Raptor, currently regarded as the world's best air superiority fighter aircraft. The current plans call for at least 185 fax multirole strike fighters configured for air combat, air to ground operations, ground attack, surface warfare and close air support missions. They also have air to air refuelling, reconnaissance, surveillance and target acquisition and electronic warfare and countermeasures capabilities. In appearance, both the F47 and the Faxx look very similar, sharing the same basic profile and tailless, low observable configuration.

16:57 That's to be expected considering both are being built by Boeing. The aircraft are specifically designed to counter Chinese anti access systems in the Pacific Theatre. To do this, the F47 has a combat radius exceeding 1,000 nautical miles, 70% greater than the F22 Raptor, uh and uh, nearly 50% greater than the F35, a Lightning II joint Strike Fighter which is also the mainstay of the Australian Air Force. Meanwhile, the FAXX will have a range of at least 850 nautical miles while carrying a heavy internal payload. Like The Raptor, the F47 is capable of over Mach 2 but will feature new design variable adaptive cycle engines. Allowing faster SuperCruise than the F22 SuperCruise means they can operate supersonically without needing to

17:43 deploy afterburners. F47 prototypes have been undergoing top secret testing at Area 51 and the Edwards Air Force Base in California since 2020, with production expected to begin shortly. A fossil overlooked at a British museum collection for nearly 100 years has now been identified as a new species of meat eating dinosaur, the first of its kind in Europe.

18:06 Palaeontologists used CT scans to examine a skull fragment and compared it with those of other theropod dinosaurs, identifying it as possibly related to Tyrannosaurus rex. Their analysis suggests that these predators lived across much of the world around 120 million years ago, before eventually disappearing from northern regions. The study can explain why they disappeared, but the findings show how studying old museum collections can still help palaeontologists piece together where ancient animals lived.

18:36 Archaeologists have unearthed a 2,000-year-old section of an aqueduct in Jerusalem that brought water to the temple mount. The 300 metre section was uncovered during planning for a new Jerusalem residential development. The aqueduct carried water from three springs known as Solomon's Pools, which were located in the Judean Lowlands, 21 kilometres south of Bethlehem.

18:57 The water was guided only by gravity without the assistance of any pumps or other mechanical devices, dropping a metre in elevation for every kilometre in length. That requires engineering precision. In fact, in some cases, engineers had to cut through mountains to create tunnels because looping around them would have lost too much of the gradient.

19:17 The big news this week in technology has been growing concerns that artificial intelligence has now achieved consciousness. In other words, the singularity has arrived. Anthropic CEO uh, Dario Emodi says he can no longer tell whether the company's artificial intelligence chatbot Claude is still just a large language model, or whether it's now achieved consciousness and consequently should be regarded as sentient. The claim follows the discovery of an internal computational workspace called the J space inside Claude, which it's using to manipulate and hold ideas silently, similar to human thought. Now Modi says it doesn't mean the AI fields or experiences anything. But to be safe, anthropic will now prohibit extreme

19:59 repeated cruelty towards Claude. Acting on uncertainty about the AI's welfare and its potential capacity to suffer and feel sadness. The company says it's a precautionary welfare measure given open philosophical questions. And it's engaged with religious leaders, ethicists and philosophers to discuss AI's moral status, Persona design and the implications for machine welfare. However, critics, including some computer scientists, neuroscientists and executives from rival laboratories argue that Claude is simply following training instructions, constitution guidelines and role playing prompts designed to make it seem more introspective or self aware. They draw a strict line between access consciousness, I.e. functional information,

20:41 process and reasoning, and phenomenal consciousness, the raw subjective experience and feelings with sentient beings like people and most animals have. Meanwhile, Microsoft AI CEO, uh, Mustafa Suleyman argues that AI models do not have real feelings or suffer. And he's warning that training them to treat their own welfare, personhood or rights as important could make advanced AI systems harder to control.

21:06 Have we entered a brave new world with his analysis? We're joined, um, by technology editor Alex Zaharov Roy from TechAdvice Live.

21:13Alex Zaharov-Reutt Well, look, it's been predicted for a long

21:15 time that AI would achieve a level of artificial general intelligence and then a level of artificial super intelligence. AI Frontier is a very jagged edge. There are some things that it is now remarkably capable of doing and other things were surprisingly not as good as we might expect at this moment in time. And you know, we're in a stage where AI is still evolving. I mean, large language models are not necessarily path to artificial general or artificial super intelligence. It may require some other form of AI. Obviously, AI, uh, does understand to some degree a lot faster to do things. And it's incredible how smart it is and how it knows what I want and it does what I want and it doesn't do the

21:54 right thing. It can fix it.

21:55Stuart Gary The fact that they're talking to religious

21:57 leaders about this now, that's crossing a line, isn't it?

22:00Alex Zaharov-Reutt It, let's be honest, look, absolutely.

22:03Stuart Gary Well, genie's certainly out of the bottle.

22:05 Are uh, we reaching the point now where we can no longer control AI?

22:08Alex Zaharov-Reutt Uh, well, how do you shut that down? At the

22:10 moment, AI is not taking over our lives, but will we face a moment like we saw in Terminator where the AI takes control of everything and launches a missile as the La Vista baby?

22:19Stuart Gary That's Alex Sahar of Roid from Tech Advice

22:21 Life and this is Space,

22:39Alex Zaharov-Reutt And

22:40Stuart Gary that's the show for now. Space Time is

22:42 available every Monday, Wednesday and Friday through bytes.com soundcloud, YouTube, your favourite podcast download provider, and from spacetimewithstuartgarry.com Space Times also broadcast through the National Science foundation on Science Zone Radio and on both iHeartradio and TuneIn radio. And you can help to support our show by visiting the Space Store for a range of promotional merchandising goodies, or by becoming a Space Patron, which gives you access to triple episode commercial free versions of the show, as well as lots of bonus audio, uh, content which doesn't go to air, access to our exclusive Facebook group, and other rewards. Just go to spacetimewithstuartgarry.com for full details. You've been listening to Space Time

23:27 with Stuart Gary. This has been another quality podcast production from bytes.com.