Galactic Secrets: Unravelling the Milky Way's Chemical Bimodality

This is Spacetime Series twenty nine, Episode two, for broadcasts on the fifth of January twenty twenty six. Coming up on Spacetime, unraveling the Milky Way's mysterious history, how the Earth's metal was able to lock away vast amounts of water during the early magmarotion, and we look back at how astronomy was set in stones. All that and more Coming up on space Time. Welcome to Space Time with Stuart Gary. A new study claims the Milky Way galaxies, by medal stellar formation evolution may be the result of intergalactic gas rather than bursts of star formation or collisions with other galaxies. The findings reported in the monthly he Notices the Royal Astronomical Society explores the origins of a puzzling feature of the Milky Way galaxy, the presence of two distinct groups of stars with different chemical compositions, a feature known as chemical bimodality. You see when scientists study stars near the Sun, they find two main types based on the chemical makeup, specifically the amounts of iron and magnesium they contain, and these two groups form separate sequences in a chemical diagram, even though they overlap in metallicity, that is, how rich they are in heavy elements astronomers call all elements other than hydrogen and healium metals. This chemical bimodality in the Milky Way as long puzzled scientists, and this new study uses advanced computer simulations to recreate the formation of galaxies like the Milky Way in a virtual universe. The authors analyze thirty simulated galaxies looking for clues about how these chemical sequences form. Understanding the chemical history of the Milky Way helps astronomers peace together how our galaxy formed and how others like it also came to be. That includes the Milky Way's sister galaxy M three one Andromeda, in which no bimodality has been detected. It also provides clues about the conditions of the early universe and the role of cosmic gas flows and galaxy mergers. The studies lead author, Matthew Orkney from the University of Barcelona says the research shows that the Milky Way's chemical structure is not a universal blueprint and that diversity is key to understanding galactic evolution. The study reveals that galaxies like our Milky Way can develop two distinct chemical sequences of various different sorts of mechanisms. In some cases, this bimodality arises from bursts of star formation full of by periods of little activity, while in others it's the result of changes in the inflow of gas from a galaxy surroundings. Now, contrary to previous assumptions, the Milkie Ways cannibalization of a smaller galaxy known as Gaius Sausage Enceladus is not a necessary condition this chemical pattern to emerge. Now you probably haven't heard of the Gaia Sausage and Solidus galaxy before because it doesn't exist anymore. It was a dwarf galaxy that was merged into the Milky Way between eight and eleven billion years ago. In fact, at least eight globular clusters were added to the Milky Way's retinue, along with fifty billion solar masses worth of stars, gas, and dark matter as a result of this merger, and it was the last major merger of the Milky Way. But in this new study, the simulation showed that metal pool gas from the circumgalactic medium played a crucial role in forming the second sequence stars. The circumgalactic medium is a vast gaseous halo surrounding galaxies, acting as a sort of bridge between the galaxy's internal interstellar medium and the larger intergalactic medium around it. It extends from the galactic disc all the way out to the dark matter halo. It's a dynamic reservoir of gas and dust at various different temperatures and densities, ranging from hot iroonized gas to molecular clouds, and this provides fuel for new star formation and receiving enriched material from galactic outflows, playing a key role in regulating galactic growth and evolution through continuous feedback cycles. The author has found that the shape of these chemical sequences is closely linked to the Milky Way star formation history, and the study predicts that many other galaxies will also exhibit a similar diversity of chemical sequences, and ultimately this will help astronomers further refine the physical evolutionary path of our own Milky Way galaxy. This is space time still to come. How the Earth's metal was able to lock away vast amounts of water during the early magnarotion, and we look back at a study showing how astronomy is set in stones. All that and more still to come on space time. A new study has shown how much of Earth's water could have survived the planet's formation by being locked away in bridgemanite minerals deep in the Earth's mantle. The findings, reported in the journal Science, could reshape astronomy's understanding of water storage and distribution. In the early ancient Earth. As it coalesced and formed out of the protoplanetary disc some four point six billion years ago, Earth was nothing like the gentle blue planet we see today. Frequent and violent celestial impacts accredited material under the planet, and this included the cataclysmic Thea collision four and a half billion years ago, during which timer planet the size of Mars slammed into the early proto Earth, turning both bodies into a seething ocean of magma in the process creating our moon. Now, this was an environment so extreme that liquid water simply couldn't exist, leaving the entire planet resembling an inferno. Since seventy a set of the Earth's surface is now covered with oceans, the mystery of how water survived and was preserved in this early superheated, molten state has long been a subject of debate. The new studies. Lead author Dougieu from the Gangeu Institute of Geochemistry says the mineral bridgemanite was the key. It's the most abundant mineral inside the Earth's mantle, and its molecules could have acted as microscopic water containers, holding substantial amounts of water which could have effectively been locked away deep within the mantle as it crystallized from its molten state. Jew says bridgemanite would have made it possible for the early Earth to retain a substantial amount of water in the mantle as the planet solidified, and this early retained water may have been critical for transforming Earth from a fiery inferno into the habitable world we enjoy today. Previous studies, which relied on relatively low temperature experimental conditions, suggested that bridgemanite had only limited water storage capability. Sir Douan colleagues wanted to test out that hypothesis, but they faced two major challenges. First, they needed to simulate the extreme conditions found at depths exceeding six hundred and sixty kilometers below the surface in a laboratory, and secondly, they had to find some way to accurately detect water signals in bridge minite samples, some of which would have been smaller than a tenth the width of human hair at concentrations as low as just a few hundred parts per million. The authors overcame these obstacles by building a diamond anvil cell experimental setup equipped with laser heating and high temperature imaging. This allowed them to raise experimental temperatures dramatically to an extreme of around four thy one hundred degrees celsius, and this successfully recreated deep metal conditions and allowed precise measurements of equilibrium temperatures, laying the foundations for understanding temperature's role in how water is taken up by minerals. The authors used cryogenic three dimensional electron diffraction and atom probe tomography to analyze water at the micro to nanometer scale, allowing them to visualized water distribution in tiny samples, confirming that it was structurally dissolved in bridgemanite. They found that bridgemannite's water locking capacity increases significantly with increases in temperature. This means that during planet Earth's hottest magnotion phase, crystallizing bridgemanite could have retained far more water than previously thought directly, overturning that long held view that the deep lower mantle was nearly dry. The authors then modeled the crystallization of the magmasan. The simulation showed that Bridgemanite's strong water locking ability under high temperatures resulted in the planet's lower matal becoming the largest water reservoir in the solid mantle after the magniration solidified. In fact, the models suggest its storage capacity could have been anywhere between five and one hundred times greater than previous estimates. The total amount of water therefore retained in the early solid mantle could have equalled the volume of all today's oceans, and the authors go further. They put out that the deeply buried water could have acted as a sort of lubricant for Earth's massive geological engine. It lowered the melting point and viscosity of mantle rocks, thereby promoting internal circulation and plate motion, and providing the planet with sustained evolutionary vitality. Over time, the sequestered water was gradually pumped back to the surface through magmatic activity, contributing to the formation of Earth's primordial atmosphere and oceans. This space time still to calm. We look back at a study showing how some of the earliest standing stones in Britain were constructed specifically with the movements of the Sun and moon in mind, and later in the science report, a new study warns that sleep atnea could be linked to Parkinson's disease. All that and more still to calm on space time. Just ten years ago, a major breakthrough in archaeological astronomy was achieved when scientists from the Australian National University and the University of Adelaide were able to show for the very first time that the earliest standing stone monuments in Great Britain, five thousand year old Great Circles, were constructed specifically in line with the movements of the Sun and moon. The findings, published in the Journal of Archaeological Science Reports, used two and three dimensional techniques to construct quantity of tests of the patterns of alignment of the ancient standing stones. The studies lead author Girl Higginbottom says no one had ever previously been able to statistically determine that a single stone circle was constructed with astronomical phenomena in mind. She says, up until then it was all just supposition examining the oldest Great Circle stones in Scotland, Caliniche on the Isle of Lewis and Steness on the Isle of Orkney, both of which predate the more famous Stonehenge by some five hundred years is Higginbottom and colleagues found a great concentration of alignments towards the Sun and Moon at different times of their cycles, and two thousand years later, much simpler monuments were still being built in Scotland that had at least one of the same astronomical alignments as that found at the Great Circles. The stones, however, aren't just connected to the Sun and the moon. The authors discovered a complex relationship between the alignment of the stones, the surrounding landscape and horizon, and the movements of the Sun and moon across that landscape. Higginbottom says the research was final proof that ancient Britons connected the earth to the sky with their earlier standing stones, and that this practice continued along the same way for at least two thousand years. The authors found that about half the sites were surrounded by one landscape pattern, and the other half of sites were surrounded by the complete reverse. Higginbottom says these chosen surroundings would have influenced the way the sun and moon were seen, especially in the timing of their rising and setting a special time like when the moon appears at its most northerly position on the horizon, which only happens once every eighteen point six years. The authors found that at half the sites, the northern horizon is relatively higher and closer than the southern horizon, and the summer solster sun appears to rise out of the highest peak in the north. Meanwhile, the other fifty percent of sites, the southern horizon is higher and closer than the northern, and the winter solst the sun appears to rise out of these highest horizons. Higginbottom says the findings showed that these people chose to erect their great stones very precisely, both within the landscape and in relation to the astronomy they knew. She says, it shows they invested a tremendous amount of effort to do the work, and that tells us about their strong connection with their environments and how important that must have been to them for their culture and for their culture survival. This is the. First time that we've actually been able to confirm that individual circles have a complex array of orientations regarding different parts of the solar and lunar cycles. Part of the reason for that is that when people were looking at the stone circles previously, they used to look at just the orientations that they thought hit on the Sun or the moon, and they ignored those that didn't. So even if they tried to do some kind of assessment on it, they weren't approaching it in a very fully sound manner. So now we can conclude that we've done that and we've got excellent results where both the Circle of Palanish which is on the west coast, and the Isle of Lewis of Scotland and Orkney, those goone circle. Their stens most certainly say ninety seven point seven percent sure that they are set up in regards to astronomical phenomena. How did you do the research? Okay, so we had two approaches. The first one was we had to do a very specific statistical test that was developed by my colleague Roger Clay. How much debt in depth would you like me to. Go we're dealing with, Well, we're dealing with something that was five thousand years ago when these things were first set up. So obviously the sky was different. Then you had to account for all that, and also yeah, and also the landscape. Although the hills were there, nevertheless the landscape may have appeared different in terms of vegetation and that sort of thing. All these sort of things, all these environmental factors need to be considered as well. So what did you basically do? Yes, So first of course we did run programs to ensure that we knew exactly where the sun and the moon were rising and setting at this time that these stones have been shown to be erected, as scientific dating has shown for them to be erected. And then on top of that, we looked at or examined the possibility of the vegetation cover in the areas, and basically, certainly for Western Scotland it was shown that there was either very very open kind of like a scrubland equivalent and partial very open. Basically particularly on western Lewis very very open, and Western Scotland generally and on Orkney during that time it would have been much the same. So when there were trees it was very open or well sometimes just what open patches in these two particular areas, And we've looked at other areas individually. Is it difficult to put a date on these things? Can't use carbon dating for stone? I guess, so you're looking at something which is bearing somewhere near it. I guess that is carbon or how did you do it so? Well? Actually I didn't do it, but other people so, for example, a gentleman by the name of Patrick Ashmore did excavation of Calonish and they looked at the different times that specific stones were erected or not, and other activities around the stone circle. So they confirmed different kinds of dating. You do us through a burnt material, so for example wood or bone, and both have been found at Stennes and Colornish. They gave scientists a pretty good idea of when these things were erected. I guess the fact that we're seeing these sorts of stone circles throughout what we now call the British Isles, but also we'll see them in parts of Europe as well. Are we looking at and I know this is your specific area of expertise, but are we looking at something which are fairly literally a broad church? I guess something that was practiced over a wide area. Certainly standing stone monuments were placed over a wide area right know, right from Ireland until eastern Europe and beyond in fact, India, China, other places right through at slightly different times. Standing stone circles, though are certainly not as prevalent as phaps, stone rows or single standing stones and stone circles are most prevalent in the British Isles, Western Europe, Vain, Portugal, got few in Scandinavia, no firm confirmed circles in Germany, but lots of standing stones. The circles tend to be part of a burial monument as opposed to a separate standing stone circle. But there are great patches through the European continent where people chose to continue building their monuments in wood and earth. So there's a very interesting division there between the groups of people who adopted the megalithic culture and those who didn't. And we're still we're actually starting to look into that. Now. Does it go with trade? Good interesting question. I think that in the very very early days of when for example, agriculture was first coming in through Europe, I think that that is a possibility. I think it would have been trade, but also the movement of peoples, because sometimes people brought this different and a new it's called the Neolithic agriculture and the New Stone Age coming through parts of Europe such as southeastern Europe and moving through Central Europe, and other times it was trade. So it would be a combination. Nothing simple. I'm afraid is it just for agricultural purposes or is there more? Two of them that or we really have are the stones? There's no written work associated with this. What do you surmise from what you've done? I think there are two very important things going on. They're both partly entwined, and that is I think that the standing stones are in places that people already knew about, but at these places, and I'll explain this because it's something that we haven't really touched on, is that the standing stones in Britain at least are in very specific places we've discovered which allow you to view the sun and the moon from very specific perspectives. So for instance, you can at half the site see one perspective and loosely speaking, and at the other half of the sites another perspective. And so the first perspective is that when you're standing at your stone circle, that you will have the northern horizon very high and quite close to you Relatively, the south will be very distant and low compared to the north. The summer solstice sun will rise out of the highest peak in the northeast, out of this range or hillock or mountain, depending on the landscape, and set in the high mountain in the north west. If it turns south, the winter solstice sun will rise and set out of little hills or there could be mountains at a great distance from the southeast and set into a hill in the southwest. And often it will travel over water to do so. And so you have all these amazing setups at them done that can only be viewed at these specific locations. And what we discovered that we discovered that for scores of sites in western Scotland which are Bronze Age about fifteen hundred BC, so that's about three and a half thousand years ago. And we now know those two great circles we talked about at the beginning have the same setup. And to get back to your question, therefore, they know about these places already, so I don't think that they're already agricultural, because as soon as they'd built standing stones, they already knew about those places before agriculture had come. Agriculture was coming into that area at that time, they were mainly heard us, but they did do some agriculture, but it wasn't as big as it was down south, so to speak. Added to that, then, I think that what they've done is actually represent their cosmological understanding of the universe and through these standing stones and how they see the sunrise and set out of those very special setups that they've done, they're showing themselves and it represents the cycle that they understand that the universe works as a cycle that is a cycle of themselves workers opposition. So you've got day and night, the sun rising in the north for example at summer solstice, the full moon that can only rise in the south at the summer solstice if it's at its most extreme rising and setting point, which only occurs every eighteen point six years, and all these kind of complicated things go on enough information in fact, that they could even if they wanted to predict the clips, if they knew about that sort of thing. It is a very detailed culture, isn't it. It is very detailed and very complex, very complex, and it's also linked to the cult of the dead, because you will always find the dead associated with standing stones. That was my next question. Are they burial sites nearby? So I guess you've just. Answered that yes, and in very very different ways. When they're associated directly with the standing stones, they're very frequently cremated dead, and you get parts of people's bodies placed, cremated bones that is placed in the socket of the standing stone, so they put them before they put the people in, or parts of them before they put the standing stone there. And then they may also put a chromated burial inside a jar and bury that next to the standing stone, or it may in fact be next to where they bury the cremation in a stone slab coffin underneath the ground and put a nice stone stone monument over that, you know, array of a can we call it. So the dead are associated in many different ways with these standing stones, and Stonehenge itself is known to have many many dead associated with it. With some standing stands. I believe there's also evidence of festivals associated without animal bones, things like that. Oh, yes, we've got something very similar also happened that Stanaz, so certainly nearby there may have actually been major festivals occurring, whether that's in association with the dead or not as well. I am unsure, but they've also found bones that are associated with specific seasons in relation to areas near Stonehenge, and they've decided they may well have been the special gathering times that people met together for either trade or other kinds of other kinds of connections between groups across a large area. That's doctor Gail Higginbottom from the Australian National University and the University of Adelaide. And this is space time and time now to take a brief look at some of the other stories making news in science this week. With the Science Report, new researchers found that obstructive sleep atnia, a condition in which some people briefly stop breathing during sleep, may increase your risk of developing Parkinson's disease. The findings are reported in the Journal of the American Medical Association. Based on research involving the health records of eleven million people, the author has found that those who would be diagnos with obstructive sleep apnea at a small increase in their risk of Parkinson's disease, around one point six extra cases per one thousand people. The study also found that Treating sleep apnea early using a breathing device called seapac could reduce that risk. A new analysis has found that one in seven deep waterage sharks and rays are now threatened with extinction. The findings, reported in the journal Science, show the biggest threat coming from overfishing. Scientists say that deep water sharks and rays, species that spend most of their life at depths greater than two hundred meters, are the most sensitive marine vertebrates to over exploitation because of their long life spans and low reproductive rates. A new study has shown that teenage girls are clocking close to six hours a day on their smartphones. The findings, reported in the Journal of the Archives of Disease in Childhood say that a large proportion of these kids are likely addicted to social media. The authors recruited oney one hundred and sixty four fifteen and sixteen year old girls from Finland and collected data on their daily smartphone use. They looked at how frequently they were picking up their phones and found the vast majority but looking at their smartphones at least three hundred and fifty six times every day. Using measurements of addiction, anxiety, and body separation, authors found seventeen percent of the teens are possibly addicted to social media, and over a third score above the potential cutoff for potential anxiety disorder. Daily time spent on social media was associated with a lower grade point average, higher social media addiction scores, higher levels of anxiety, poor a body image, poor a health, lower mood, more tiredness, and greater feelings of loneliness. To quote the immortal doctor Shuldon Cooper, there is absolutely no scientific evidence to support clear voids of any kind. That means that fortune telling is a fraud, profession is a swindle, and its livelihood is dependent on the gullibility of stupid people. To help underlying those words, a bunch of psychics have been put to the test, and again they've foiled miserably. This later study, reported in the General Brand and Cognition, was a double blind test to determine a psychic's ability to determine the cause of death of a group of subjects skeptics. Ten Menum says, not only did the mediums perform worse than they would have by a simple random chance, but non psychics brought into the control group who claim no special spiritual psychic or supernatural powers actually did better than the psychics. There's been a lot of tests done over the years. Over the last one hundred years, I've pitted with suppose that psychic skills, et cetera from the old Zena cards, you know, with the cross of the circle on the square, and that's sort of past to try and say which card is which. A big part of the psychic movement is obviously contacting the dead, which has been described as grief vampires, to actually sort of pick up people are quite distraught as having lost the relatives, well everyone, and then I say I can contact them and say, you know, uncle Harry is very happy up here and he still loves you. So for some people tried to put some of this to the tests and how he approve they're not contacting the death, or how do you prove they are. It's only a fairly small number of mediums. This was in the United States. Gathered a small number of mediums and they were showing one hundred and eighty photographs of people who had died, but the photographs were taken up several years before they died, and the task they gave these mediums was to determine the cause of death, choosing among options such as gun shot, hard attack, or car accidents, so fairly traumatic events, not just that it's dying of old age. And the group had toes that decided how they died. And if they're contacting the people after death, they should be able to say a dying the car crash or they should have known. They also had a group of ordinary people like non mediums, people who don't claim any psychic ability, to do the same test to see how they have a control see how they would work out. And as it worked out, it showed that when the ordinary people were looking at the photographs, their heart rate was fairly normal. When the mediums were looking at the photographs, their heart rates shot up. Are they're under stress and put it this way, they didn't do well the mediums. I think they did rather poorly. The control group did better at choosing the reason for death than the mediums did not a lot out about four percent higher, and the medium scored zero point two percent lower than chance predictions, which means they're pretty much on chance, which means they're pretty much guesswork. So these are the tests. These quantitative tests are very worthwhile doing. To have a look at sort of to see if people can actually do what they claim they can do it, Like the skeptics offer one hundred thousand dollars for anyone who can prove what they claim they can do under such scientific conditions with these tests. Of course it's a bit imperfect. A small number of mediums, but this was pretty straightforward, and these people said that they could do it. They make their living at it. During this it's a pretty important issue, the medium said. They reported feeling the pain of the individuals, but they are unable to pinpoint the exact causes, which is I think there's a technical term for this. And so did have their Senate as well, because these are people who make their living by contacting the dead and passing on the information to their relatives and saying, I've got uncle Harry on the line. He says he still loves you. Watch after that car, watch out for this out and the other. So they can give specific information, never specific enough to show that where the money is buried, but specific information, and not from the dead person where they can't say how the person died. In fact, they often claim that I was sick, they had a bad problem, they had a health issue, they had lung issues whatever. When you when you have a problem at some stage. Anyone's got a health problem. Everyone's got a back problem, by the way. But when they are in a medium client situation, they can claim all sorts of things about health. But when they put down to this, they're showing a photo of something which they claim to be able to contact enough to know that they're in pain. They can't say how they died. And I would suggest that me personally, I'm going to be it on the nasty stide of the skeptics. They would say, most people who were claiming they can talk to the dead, they are actually not and know they're not. Others might thing they are. The artists, Yeah, and grifters. That's the skeptics timendum, and this is space Time, and that's the show for now. Speak Time is available every Monday, Wednesday and Friday through bytes dot com, SoundCloud, YouTube, your favorite podcast download provider, and from space Time with Stuart Gary dot com. Space Time's also broadcast through the National Science Foundation, on Science Own Radio and on both iHeartRadio and tune In Radio. And you can help to support our show by visiting the Spacetime store for a range of promotional merchandising goodies, or by becoming a Spacetime Patron, which gives you access to triple episode commercial free versions of the show, as well as lots of burnus audio content which doesn't go to weir, access to our exclusive Facebook group, and other rewards. Just go to space Time with Stuart Gary dot com for full details. You've been listening to space Time with Stuart Gary. This has been another quality podcast production from bytes dot com.