Philippa Kaur

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    in Space & Astronomy

    Saturn has a fuzzy core, spread over more than half the planet’s diameter

    One of Saturn’s rings has revealed properties of its core, hidden deep beneath the planet’s golden atmosphere.

    That core isn’t the lump of rock and ice that many scientists had envisioned, the new study finds. Instead, the core is diffuse, pervaded by huge amounts of hydrogen and helium and so spread out that it spans 70,000 kilometers, or about 60 percent of the planet’s diameter, researchers report April 28 at arXiv.org.

    The new intel should help planetary scientists better understand not only how giant planets formed in our solar system but also the nature of such worlds orbiting other stars.  

    To ascertain the structure of Saturn’s core, astronomer Christopher Mankovich and astrophysicist Jim Fuller, both at Caltech, examined the giant planet’s rings. Just as earthquakes help seismologists probe Earth’s interior, oscillations inside Saturn can reveal its internal composition. These oscillations alter Saturn’s gravitational forces, inducing waves in the rings —especially the C ring, which is the nearest of the three main rings to the planet (SN: 1/22/19).

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    By analyzing a wave in that ring, along with data on Saturn’s gravity field from the now-defunct Cassini spacecraft (SN: 9/15/17), Mankovich and Fuller found that the core has about 17 Earth masses of rock and ice. But there’s so much hydrogen and helium mixed in, the core encompasses 55 Earth masses altogether — more than half of Saturn’s total, which is equivalent to the mass of 95 Earths. This “ring seismology” work will appear in a future Nature Astronomy.

    “It’s a new way to look at gas giant planets in the solar system,” says Ravit Helled, a planetary scientist at the University of Zurich who was not involved with the work. “This knowledge is important because it reflects on our understanding of giant exoplanets,” and indicates that giant planets in other solar systems probably have more complex structures than many researchers had thought.

    The discovery also illuminates how Saturn formed, says Nadine Nettelmann, a planetary scientist at the German Aerospace Center in Berlin.

    Older theories posited that a gas giant such as Saturn arises when rock and ice orbiting the sun start to conglomerate. Tenuous gaseous envelopes let additional solid materials sink to the center, forming a compact core. Only later, according to this theory, does the core attract lots of hydrogen and helium — the ingredients that make up most of the planet. Although these elements are gases on Earth, Saturn’s great gravity squeezes most of them into a fluid.

    But newer theories say instead that plenty of gas got incorporated into the core of rock and ice when it was taking shape 4.6 billion years ago. As the planet accreted additional mass, the proportion of gas rose. The structure Mankovich and Fuller deduce for Saturn’s core preserves this formation history, Nettelmann says, because the planet’s very center, representing the oldest part of Saturn, has the greatest proportion of rock and ice. The fraction of rock and ice decrease gradually rather than abruptly from the core’s center to its edge, reflecting the core’s development over time.

    “I find the conclusions very important and very exciting and the line of reasoning very convincing,” Nettelmann says. Still, she cautions that additional waves in the rings should be analyzed for confirmation.

    The type of oscillation that Mankovich and Fuller detect inside Saturn also implies that the core is stable rather than bubbling like a pot of water on a hot stove, which is one way a planet can carry heat from its hot interior outward. The core’s stability may help explain a long-standing puzzle: why Saturn emits more energy than it gets from the sun.

    After the planet formed, it was warm with the heat of its birth, but then it cooled off. The core’s stability could have put a lid on some of this cooling, however, which helped the planet retain heat that it still radiates to this day. In contrast, if the core had instead transported heat via the upwelling and downwelling of material, the planet would have cooled off faster and no longer give off so much heat. More

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    in Humans

    Older children in the year group are more popular than younger peers

    By Karina Shah

    Older teenagers in a year group tend to be more popularStockbroker/MBI/Alamy
    Older teenagers tend, on average, to be more popular than their younger peers in the same class.
    Danelien van Aalst at the University of Groningen in the Netherlands and her colleagues have investigated how relative age affects popularity among 14 to 15-year-olds in the Netherlands, Sweden and England. They collected survey data from 13,251 students from the three countries, who were quizzed between October 2010 and April 2011.

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    Each teenager was asked to identify five of the most popular students in their class. The researchers then compared the popularity of each child to their age relative to that of their peers. They discovered a correlation: the older the student was, the more likely they were to be considered popular.
    “A child enters school before or after a certain cut-off date and that determines how old or young you are relative to your year group,” says van Aalst. “We found that if you’re born right after the cut-off date [making you one of the oldest members of your class], you’re going to be popular.”

    They found that the same effect also applied at the year-group level. Here, it was the children who were oldest relative to all of their peers in the year group – rather than just those in their particular class – that were the most popular.
    All three countries showed roughly the same pattern. However, at the year-group scale, it was most pronounced in England.
    At the classroom level, it was in the Netherlands that the pattern was strongest. This is partly because the country has a system of grade retention – when students don’t meet their academic requirements, their teachers will hold them back a year, which means they then become the oldest in their class and often the most popular.
    This relative age effect has been shown in other areas. “Relative age has earlier been demonstrated to affect school performance – relatively older children do better in school,” says Herman van de Werfhorst at the University of Amsterdam, who wasn’t involved in the study.
    Similarly, previous research has shown that older children tend to be better at sports than younger students in the same year group.
    Journal reference: PLoS One, DOI: 10.1371/journal.pone.0249336

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    in Humans

    What to cook if covid-19 has affected your sense of smell and taste

    By Sam Wong

    OksanaKiian/Getty ImagesFOR many of us, food has been one of the most dependable pleasures in a year when so many normal activities have been put on hold. It seems particularly cruel that a common, lingering symptom of covid-19 is an altered sense of taste and smell, with studies finding that between 40 and 85 per cent of people with the illness experience some loss of these senses.
    The virus that causes covid-19 attaches to ACE2 proteins in the olfactory epithelium, the tissue inside the nose where our smell receptors are located. Once the virus enters these cells, … More

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    in Humans

    Don't Miss: Netflix's Oxygen, a sci-fi thriller with a shocking twist

    Shana Besson/Netflix
    Watch
    Oxygen, Alexandre Aja’s sci-fi thriller, is the story of a woman with amnesia (Mélanie Laurent) who is trapped in a cryogenic chamber. Her oxygen is running out and she will survive only if she remembers who she is. On Netflix from 12 May.

    Read
    Crooked Cats tell their own bloody tales in anthropologist Nayanika Mathur’s study of how big cats – tigers, leopards and lions – come to prey on humans. Ecological collapse is an important reason why such attacks occur, but is it the whole story?
    Pushkin House
    Last chance
    Cosmos: Reverse perspective looks at Earth from space through collages and graphics, capturing the changes we have lived through since Yuri Gagarin’s first orbit. Online from Pushkin House until 18 May. More

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    in Humans

    Disco Elysium examines the mystery of how we construct our identity

    By Jacob Aron

    ZA/UM
    Disco Elysium
    ZA/UM
    PC, PlayStation 4 and 5, Xbox One, Series X and S

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    YOU wake up, unable to remember anything about your life or how you got here. This is the opening of so many video games that an amnesiac protagonist has become something of a cliché.
    But Robert Kurvitz, lead writer and designer of Disco Elysium prefers to see it as an essential part of video game storytelling. “There’s a promise of newness and being someone else, and for that the player needs to forget who they were,” he told me when we spoke after the game’s recent console release.
    To be fair, Disco Elysium doesn’t quite start with waking up. The game’s first words are uttered by your ancient reptilian brain, which you engage in a conversation about whether to become conscious. Soon, your limbic system joins the exchange as you become increasingly aware of your surroundings, before waking up half-naked and hung-over. It is a unique and arresting beginning.
    Stumbling out of your hotel room and speaking to the people you meet, it becomes apparent that you are a police detective trying to solve a murder, and you have been on a three-day bender, leading to complete memory loss.
    Like many role-playing games, your character has a number of skills that determine your ability to perform tasks or unlock dialogue options. But while a traditional fantasy RPG might rate you for strength or magic, Disco Elysium‘s skills are more unusual – what’s more, they talk.
    Your Encyclopaedia skill, for example, might feed you bits of information about the vaguely Eastern European setting of the game, while Composure helps you read other people’s body language and Electrochemistry pushes you towards indulging in alcohol and other addictive substances.
    Kurvitz says the team wanted to avoid presenting the skill characters as the kind of intrusive voices that might be experienced by someone with, say, dissociative identity disorder. The skills are clearly facets of one personality rather than a mental cacophony. The team wanted to simulate the way the mind works through internal monologue, says Kurvitz.
    This means that while the basic plot is about solving a murder, the game’s real concern is the construction of identity. When playing, you gain points you can invest in skills, boosting the chances of success when you use them and further moulding your personality. Increase your Drama skill and you will find it easier to be inventive and spot when people are lying; boost it too high and you could become overly dramatic.
    In addition to the skills, certain characters or experiences you come across in the game can trigger thoughts that you can choose to engage with and internalise. I found myself going for dialogue options dealing with art or creativity, which resulted in my Conceptualisation skill offering me the chance to be an “art cop”.
    The result is you can make some really strange choices about how your detective behaves, sending you deeper into Disco Elysium‘s weird world. I have been taking full advantage, but Kurvitz says it has proved surprisingly difficult to get players to embrace these options.
    To nudge people towards more interesting role playing, a message on the loading screen reassures you that making odd choices won’t mean you fail in the game.
    Perhaps the lesson is that when we are invited to reinvent ourselves, we tend to stick to the familiar.
    Jacob also recommends…
    Planescape: Torment
    Black Isle Studios
    PC, PlayStation 4, Xbox One, Nintendo Switch, Android, iOS
    This cult classic role-playing game, also starring an amnesiac protagonist, is set across a strange fantasy multiverse and was a big inspiration for Disco Elysium.

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    in Humans

    Remains of a 3-year-old child are the oldest known burial in Africa

    By Alison George

    This partial skeleton (left) and skull were discovered in a cave in KenyaMartinón-Torres, et al., 2021
    The oldest known burial in Africa is of a 3-year-old child who died around 78,000 years ago. The discovery sheds light on how people in the region cared for their dead at that time.
    In 2017, archaeologists uncovered the top of a bundle of bones in a cave in Kenya called Panga ya Saidi. The remains were so fragile that a block of sediment around the bones was extracted intact and sent to the National Research Centre on Human Evolution (CENIEH) in Spain, where a painstaking forensic investigation took place.

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    “We didn’t know until a year later what was really going on in there,” says María Martinón-Torres at CENIEH. “Unexpectedly, that sediment block was holding the body of a child.”
    The researchers named the child Mtoto, which means “child” in Swahili, and estimate that they lived around 78,300 years ago, making this the oldest deliberate burial found in Africa. “It was a child and someone gave it a farewell,” says Martinón-Torres.

    Analysis of the sediment surrounding the remains revealed that the child had been placed in a deliberately excavated pit and covered with sediment from the cave floor. They had been placed on their side with their legs drawn up to their chest. As the body decayed, most of Mtoto’s bones stayed in position with the exception of a few key ones.
    The collarbone and top two ribs were displaced in a way typical of a body tightly bound in a shroud. And Mtoto’s head had the characteristic tilt of a corpse whose head was placed on a cushion. This points to a deliberate burial, something that is often difficult to prove from archaeological remains.
    “From these little pieces of bone that were preserved, the work that we have done has allowed us to reconstruct the human behaviour surrounding the moment the body was put in the pit,” says Francesco d’Errico at the University of Bordeaux, France.

    “The authors did a fantastic job in making the case that this is a deliberate burial. They have raised the bar and, in my opinion, actually set the standard on what should be done, scientifically, to demonstrate deliberate burial,” says Eleanor Scerri at the Max Planck Institute for the Science of Human History in Germany, who wasn’t involved with the research.
    The discovery of any ancient human remains in Africa is big news in itself. “Human fossils are rare everywhere in Africa. We have huge temporal and spatial gaps, so this discovery is extremely important,” says Scerri..
    Mtoto’s burial took place in the Middle Stone Age, which spans from roughly 300,000 to 30,000 years ago, when a suite of modern human innovations developed in Africa. Early evidence of burials in Africa is rare. No buried adults have been found from this period, although the burial of an infant in Border cave in South Africa dates to around 74,000 years ago, and the burial of a child who was about 9 years old in Taramsa Hill, Egypt, dates to around 69,000 years ago.
    “I find it very interesting that we have interments of two or three children in Africa dating to around the same period,” says Paul Pettitt of the University of Durham, UK. “Mtoto’s burial is an exceptionally early example of a very rare treatment of the dead which might be commonplace in the modern world, but during the early prehistory of our species was rare, exceptional and probably marked odd deaths.”
    This lack of burials shows the mortuary practices of modern humans in Africa differed from those of Neanderthals and modern humans in Eurasia, who, from about 120,000 years ago, commonly buried their dead. “That is a quite a paradox,” says d’Errico. “In Africa, where we have the origin of symbolic behaviour in the form of beads and abstract engravings, these modern humans wait quite long to make primary burials.”
    Journal reference: Nature, DOI: 10.1038/s41586-021-03457-8
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    in Humans

    How to boost your self-awareness and make better decisions

    Having good metacognition – the ability to think about our own thoughts – is key to success in many aspects of life. Fortunately, there are things we can all do to get to know ourselves better

    Humans

    5 May 2021

    By Stephen Fleming

    Jasu Hu
    AS YOUR eyes skip across the words on this page, it is likely that you are not only reading, but also thinking about yourself reading. Are the words clear? Can you concentrate? Do you have time to read this article now or are you feeling rushed?
    Psychologists have a term for this kind of awareness of our own minds: metacognition – literally, the ability to think about our own thinking. Being able to turn our thoughts on ourselves is a defining feature of being human. But we often overlook the power it has in shaping our lives, both for good and ill. The importance of good self-awareness can seem less obvious than, say, the ability to make mathematical calculations, or remember facts. Instead, for most of us, metacognition is like the conductor of an orchestra, occasionally intervening to nudge the players in the right (or wrong) direction.
    Now, research from my lab and others is pulling back the veil on self-awareness, giving us a new-found respect for the power of the reflective mind. We have found ways to measure it, and can even watch it in action using brain scanners. What we have discovered is already suggesting a rethink in our understanding of conditions like dementia, but it has implications for us all. Boosting self-awareness can improve our decisions, open our eyes to fake news and help us think clearly under pressure. Just as a good conductor can make the difference between a routine rehearsal and a world-class performance, the subtle influence of metacognition can make the difference between failure and success in many aspects of life.
    We rely … More

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    in Space & Astronomy

    A rare glimpse of a star before it went supernova defies expectations

    A rare glimpse of a star before it exploded in a fiery supernova looks nothing like astronomers expected, a new study suggests.

    Images from the Hubble Space Telescope reveal that a relatively cool, puffy star ended its life in a hydrogen-free supernova. Until now, supernovas without hydrogen were thought to originate only from extremely hot, compact stars.

    The discovery “is a very important test case for stellar evolution,” says Sung-Chul Yoon, an astrophysicist at Seoul National University in South Korea, who was not involved in the work. Theorists have some ideas about how massive stars behave right before they blow up, but such hefty stars are scant in the local universe and many are nowhere near ready to go supernova, Yoon says. Retroactively identifying the star responsible for a supernova provides an opportunity to test scenarios of how stars evolve right before exploding.

    Finding those stars, however, is difficult, explains Charlie Kilpatrick, an astronomer at Northwestern University in Evanston, Ill. A telescope must have looked at that exact region of the sky in the years leading up to the supernova. And the explosion must have happened close enough for light from its much fainter source star to have reached a telescope.

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    Although both conditions are tricky to meet, Kilpatrick is undaunted by the hunt. After scientists discovered a supernova in December 2019, in a galaxy called NGC 4666 about 46 million light-years away, he and colleagues rushed to check old Hubble observations from the same region of the sky. They wanted to find the star behind the explosion, dubbed SN 2019yvr.

    After pouring over images and cross-checking observations with those from ground-based telescopes, the team found their quarry: a star at the same spot as the supernova, observed about 2.6 years before the explosion. It appeared to be a yellow star about 6,500° Celsius and about 320 times wider than the sun.

    “I was kind of puzzled by all that,” Kilpatrick says. The supernova SN 2019yvr lacked hydrogen, so its progenitor was expected to be hydrogen-deficient, too. But “if a star lacks a hydrogen envelope, then you expect to be seeing deeper inside of the star to the hotter layers,” Kilpatrick says. That is, the star should have looked extremely hot and blue and compact — maybe 10,0000 to 50,000° C, and no more than 50 times wider than the sun. The cool, large, yellow progenitor of SN 2019yvr, on the other hand, appeared to be padded with lots of hydrogen. The researchers report the results May 5 in the Monthly Notices of the Royal Astronomical Society.

    For this kind of star to have produced a supernova like SN 2019yvr, it must have shed much of its hydrogen before blowing up, Kilpatrick says. But how?

    He and colleagues have come up with a couple scenarios. The star could have expelled much of its hydrogen into space through violent eruptions, possibly caused by some instability in the star’s core or interference from another star nearby. Or perhaps the star’s hydrogen could have been stripped off by another star that was in orbit around it.

    To whittle these possibilities down, Jan Eldridge, an astrophysicist at the University of Auckland in New Zealand, suggests turning the Hubble telescope back on that area of the sky. Astronomers should first make sure that the star seen 2.6 years before SN 2019yvr really is gone now, says Eldridge, who was not involved in the work. Researchers could also check whether a star that once orbited SN 2019yvr’s progenitor still remains.

    “They’ve found a mystery, and they’ve got some solutions,” Eldridge notes. Trying to figure out how such an unlikely star pulled off this particular supernova, she says, “is going to be fun.” More