Philippa Kaur

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    in Space & Astronomy

    Souped-up supernovas may produce much of the universe’s heavy elements

    Violent explosions of massive, magnetized stars may forge most of the universe’s heavy elements, such as silver and uranium.

    These r-process elements, which include half of all elements heavier than iron, are also produced when neutron stars merge (SN: 10/16/17). But collisions of those dead stars alone can’t form all of the r-process elements seen in the universe. Now, scientists have pinpointed a type of energetic supernova called a magnetorotational hypernova as another potential birthplace of these elements.

    The results, described July 7 in Nature, stem from the discovery of an elderly red giant star — possibly 13 billion years old — in the outer regions of the Milky Way. By analyzing the star’s elemental makeup, which is like a star’s genetic instruction book, astronomers peered back into the star’s family history. Forty-four different elements seen in the star suggest that it was formed from material left over “by a special explosion of one massive star soon after the Big Bang,” says astronomer David Yong of the Australian National University in Canberra.

    The ancient star’s elements aren’t from the remnants of a neutron star merger, Yong and his colleagues say. Its abundances of certain heavy elements such as thorium and uranium were higher than would be expected from a neutron star merger. Additionally, the star also contains lighter elements such as zinc and nitrogen, which can’t be produced by those mergers. And since the star is extremely deficient in iron — an element that builds up over many stellar births and deaths — the scientists think that the red giant is a second-generation star whose heavy elements all came from one predecessor supernova-type event.

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    Simulations suggest that the event was a magnetorotational hypernova, created in the death of a rapidly spinning, highly magnetized star at least 25 times the mass of the sun. When these stars explode at the end of their lives as a souped-up type of supernova, they may have the energetic, neutron-rich environments needed to forge heavy elements.

    Magnetorotational hypernovas might be similar to collapsars — massive, spinning stars that collapse into black holes instead of exploding. Collapsars have previously been proposed as birthplaces of r-process elements, too (SN: 5/8/19).

    The researchers think that magnetorotational hypernovas are rare, composing only 1 in 1,000 supernovas. Even so, such explosions would be 10 times as common as neutron star mergers today, and would produce similar amounts of heavy elements per event. Along with their less energetic counterparts, called magnetorotational supernovas, these hypernovas could be responsible for creating 90 percent of all r-process elements, the researchers calculate. In the early universe, when massive, rapidly rotating stars were more common, such explosions could have been even more influential.

    The observations are impressive, says Stan Woosley, an astrophysicist at the University of California, Santa Cruz, who was not involved in the new study. But “there is no proof that the [elemental] abundances in this metal-deficient star were made in a single event. It could have been one. It could have been 10.” One of those events might even have been a neutron star merger, he says.

    The scientists hope to find more stars like the elderly red giant, which could reveal how frequent magnetorotational hypernovas are. For now, the newly analyzed star remains “incredibly rare and demonstrates the need for … large surveys to find such objects,” Yong says. More

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    in Humans

    What forms can consciousness take and can we see it in our brains?

    New insights into the different states of human consciousness and where it occurs in the brain are helping us crack the mystery of what gives rise to felt experience

    Humans

    7 July 2021

    By Emma Young

    Eva Redamonti
    What is consciousness?
    In essence, consciousness is any kind of subjective experience. Being in pain; smelling onions frying; feeling humiliated; recognising a friend in the crowd; reflecting that you are wiser than you were last year – all of these are examples of conscious experiences. In a field fraught with disagreements, this is something that most, but not all, researchers agree on. Go any deeper, though, and the rifts open up.
    The 17th-century French philosopher René Descartes famously divided the universe into “matter stuff”, such as rocks and physical bodies, and “mind stuff”. In the 20th century, philosopher David Chalmers at New York University built on Descartes’s separation, known as “dualism”, and the work of later thinkers, to distinguish between “easy problems of consciousness” and “the hard problem”.
    The easy stuff consists of explaining the brain processes associated with consciousness, such as the integration of sensory information, learning, thinking and being awake or asleep. Though we are making steady progress, these problems have yet to be cracked: they are easy only in the sense that the known strategies of cognitive and neuroscientific research should eventually provide full explanations.
    The hard problem, which Chalmers introduced at a scientific meeting in 1994, is to explain why and how we have subjective experiences at all. “Consciousness poses the most baffling problem in the science of the mind,” Chalmers said. When we think and perceive, there is a “whir of information-processing” in the brain, as he put it, but also very distinctive subjective states of mind. The puzzle is how a 1.3 kilogram organ with the consistency of tofu can generate the feeling of being. … More

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    in Humans

    Can physics explain consciousness and does it create reality?

    We are finally testing the ideas that quantum collapse in the brain gives rise to consciousness and that consciousness creates the reality we see from the quantum world.

    Humans

    7 July 2021

    By Anil Ananthaswamy

    If physical processes in a brain create consciousness, what are they?Victor de Schwanberg/Science Photo Library
    If physics explains all the phenomena in the universe, and if consciousness is part of the universe, then is seems that physics can explain consciousness.
    Of course, this assumes that consciousness isn’t separate from the material reality that physics explains – which runs counter to René Descartes’s dualist view of mind and matter. Some have no problem with that. They include Daniel Dennett at Tufts University in Massachusetts and Michael Graziano at Princeton University, who argue that our intuitive sense that consciousness needs an explanation that goes beyond objective descriptions of the physical world is misplaced. Consciousness is a mirage produced by sophisticated neural mechanisms in the brain, they contend, so we need no new physics to explain it. Rather, we need a better understanding of how the brain creates models: of the world, of a self in the world and of a self subjectively experiencing the world.

    Other non-dualists don’t outright deny that consciousness may have unusual properties that need explaining. If they are correct, then quantum mechanics may offer an explanation.
    Quantum systems can exist in a superposition of all possible states simultaneously, and classical reality emerges when this superposition collapses into a single state. One idea is that this happens when the mass of a quantum system … More

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    in Space & Astronomy

    A shadowy birthplace may explain Jupiter’s strange chemistry

    Jupiter may have formed in a shadow that kept the planet’s birthplace colder than Pluto. The frigid temperature could explain the giant world’s unusual abundance of certain gases, a new study suggests.

    Jupiter consists mostly of hydrogen and helium, which were the most common elements in the planet-spawning disk that spun around the newborn sun. Other elements that were gases near Jupiter’s birthplace became part of the planet, too, but in only the same proportions as they existed in the protoplanetary disk (SN: 6/12/17).

    Astronomers think the sun’s composition of elements largely reflects that of the protoplanetary disk, so Jupiter’s should resemble that solar makeup — at least for elements that were gases. But nitrogen, argon, krypton and xenon are about three times as common on Jupiter, relative to hydrogen, as they are on the sun.

    “This is the main puzzle of Jupiter’s atmosphere,” says Kazumasa Ohno, a planetary scientist at the University of California, Santa Cruz. Where did those extra elements come from?

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    If Jupiter was born at its current distance from the sun, the temperature of the planet’s birthplace would have been around 60 kelvins, or –213˚ Celsius. In the protoplanetary disk, those elements should be gases at that temperature. But they would freeze solid below about 30 kelvins, or –243˚ C. It’s easier for a planet to accrete solids than gases. So if Jupiter somehow arose in a much colder environment than its current home, the planet could have acquired solid objects laden with those extra elements as ice.

    For this reason, in 2019 two different research teams independently made the radical suggestion that Jupiter had originated in the deep freeze beyond the current orbits of Neptune and Pluto, then spiraled inward toward the sun.

    Now Ohno and astronomer Takahiro Ueda of the National Astronomical Observatory of Japan propose a different idea: Jupiter formed where it is, but a pileup of dust in between the planet’s orbit and the sun blocked sunlight, casting a long shadow that cooled Jupiter’s birthplace. The frosty temperature made nitrogen, argon, krypton and xenon freeze solid and become a greater part of the planet, the scientists suggest in a study in the July Astronomy & Astrophysics.

    The dust that cast the shadow came from rocky objects closer to the sun that collided and shattered. Farther from the sun, where the protoplanetary disk was colder, water froze, giving rise to objects that resembled snowballs. When those snowballs collided, they were more likely to stick together than shatter and thus didn’t cast much of a shadow, the researchers say.

    “I think it’s a clever fix of something that might have been difficult to rectify otherwise,” says Alex Cridland, an astrophysicist at the Max Planck Institute for Extraterrestrial Physics in Garching, Germany.

    Cridland was one of the scientists who had suggested that Jupiter formed beyond Neptune and Pluto. But that theory, he says, means Jupiter had to move much closer to the sun after birth. The new scenario avoids that complication.

    Measuring the atmospheric composition of Saturn may pinpoint the birthplace of Jupiter.NASA, ESA, A. Simon/GSFC, M.H. Wong/UCB, the OPAL Team

    How to test the new idea? “Saturn might hold the key,” Ohno says. Saturn is nearly twice as far from the sun as Jupiter is, and the scientists calculate that the dust shadow that chilled Jupiter’s birthplace barely reached Saturn’s. If so, that means Saturn arose in a warmer region and so should not have acquired nitrogen, argon, krypton or xenon ice. In contrast, if the two gas giants really formed in the cold beyond the present orbits of Neptune and Pluto, then Saturn should have lots of those elements, like Jupiter.

    Thanks to the Galileo probe, which dove into the Jovian atmosphere in 1995, astronomers know these abundances for Jupiter. What’s needed, the researchers say, is a similar mission to Saturn. Unfortunately, while orbiting Saturn, the Cassini spacecraft (SN: 8/23/17) measured only an uncertain level of nitrogen in the Ringed Planet’s atmosphere and detected no argon, krypton or xenon, so Saturn doesn’t yet constrain where the two gas giants arose.     More

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    in Humans

    Richard Lewontin: Pioneering evolutionary biologist dies aged 92

    By New Scientist

    Museum of Comparative Zoology, Harvard
    Richard Lewontin, the geneticist and evolutionary biologist whose research showed that humans from different ethnic backgrounds aren’t as genetically different as appearances might suggest, has died at the age of 92.
    Lewontin’s work revealed that nearly 85 per cent of humanity’s genetic diversity is seen between individuals of a single population, such as those of a single nation. A further 8 per cent occurs between such populations that might have been put into the same racial category. Differences between ethnic groups accounted for just 7 per cent of genetic diversity. Simply put: two people are different because they are … More

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    in Humans

    First farmers in the Atacama Desert had a history of brutal violence

    By James Urquhart

    An aerial view of coastal area of Llanos de Challe National Park in the Atacama Desertabriendomundo/Getty Images
    When coastal hunter-gatherers settled inland to begin farming about 3000 years ago in the Atacama desert, their violence became more gruesome, often with intent to kill, according to a study of human remains from the time.
    Vivian Standen at the University of Tarapacá in Chile and her colleagues studied signs of violence in the remains of 194 adults buried between 2800 and 1400 years ago in a coastal desert valley of northern Chile.
    The team … More

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    in Space & Astronomy

    Scientists spotted an electron-capture supernova for the first time

    A long-predicted type of cosmic explosion has finally burst onto the scene.

    Researchers have found convincing evidence for an electron-capture supernova, a stellar explosion ignited when atomic nuclei sop up electrons within a star’s core. The phenomenon was first predicted in 1980, but scientists have never been sure that they have seen one. A flare that appeared in the sky in 2018, called supernova 2018zd, matches several expected hallmarks of the blasts, scientists report June 28 in Nature Astronomy.

    “These have been theorized for so long, and it’s really nice that we’ve actually seen one now,” says astrophysicist Carolyn Doherty of Konkoly Observatory in Budapest, who was not involved with the research.

    Electron-capture supernovas result from stars that sit right on the precipice of exploding. Stars with more than about 10 times the sun’s mass go supernova after nuclear fusion reactions within the core cease, and the star can no longer support itself against gravity. The core collapses inward and then rebounds, causing the star’s outer layers to explode outward (SN: 2/8/17). Smaller stars, with less than about eight solar masses, are able to resist collapse, instead forming a dense object called a white dwarf (SN: 6/30/21). But between about eight and 10 solar masses, there’s a poorly understood middle ground for stars. For some stars that fall in that range, scientists have long suspected that electron-capture supernovas should occur.

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    During this type of explosion, neon and magnesium nuclei within a star’s core capture electrons. In this reaction, an electron vanishes as a proton converts to a neutron, and the nucleus morphs into another element. That electron capture spells bad news for the star in its war against gravity because those electrons are helping the star fight collapse.

    According to quantum physics, when electrons are packed closely together, they start moving faster. Those zippy electrons exert a pressure that opposes the inward pull of gravity. But if reactions within a star chip away at the number of electrons, that support weakens. If the star’s core gives way — boom — that sets off an electron-capture supernova.

    But without an observation of such a blast, it remained theoretical. “The big question here was, ‘Does this kind of supernova even exist?’” says astrophysicist Daichi Hiramatsu of the University of California, Santa Barbara and Las Cumbres Observatory in Goleta, Calif. Potential electron-capture supernovas have been reported before, but the evidence wasn’t definitive.

    So Hiramatsu and colleagues created a list of six criteria that an electron-capture supernova should meet. For example, the explosions should be less energetic, and should forge different varieties of chemical elements, than more typical supernovas. Supernova 2018zd checked all the boxes.

    A stroke of luck helped the team clinch the case. Most of the time, when scientists spot a supernova, they have little information about the star that produced it — by time they see the explosion, the star has already been blown to bits. But in this case, the star showed up in previous images taken by NASA’s Hubble Space Telescope and Spitzer Space Telescope. Its properties matched those expected for the type of star that would produce an electron-capture supernova.

    “All together, it really is very promising,” says astrophysicist Pilar Gil-Pons of Universitat Politècnica de Catalunya in Barcelona. Reading the researchers’ results, she says, “I got pretty excited, especially about the identification of the progenitor.” 

    Finding more of these supernovas could help unveil their progenitors, misfit stars in that odd mass middle ground. It could also help scientists better nail down the divide between stars that will and won’t explode. And the observations could reveal how often these unusual supernovas occur, an important bit of information for better understanding how supernovas seed the cosmos with chemical elements. More

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    in Humans

    A Psalm for the Wild-Built by Becky Chambers is joyful sci-fi reading

    The relationship between a robot and a monk is at the heart of a new bookZoonar GmbH/Alamy
    A Psalm for the Wild-Built
    Becky Chambers
    Tor.comAdvertisement

    I READ a lot of sci-fi and, my, the future can be grim at times. Whether it is characters dealing with alien invasions, technology gone wrong or the ravages of climate change, most modern books in the genre are dour affairs, in stark contrast to the “golden age” sci-fi of the 1940s and 50s, when unrealistic techno-utopianism ruled.
    But it isn’t all bad. Increasingly, authors are writing “hopepunk” stories (a slightly cringeworthy term inspired by cyberpunk) that weaponise optimism, according to one Vox journalist.
    At the forefront of this subgenre is Becky Chambers, award-winning author of the Wayfarers series. But unlike the golden age stories, Chambers’s characters live complex lives and know that not all problems can be tackled with the wave of a plot-solving gizmo. Instead, they rely on relationships to succeed, picking each other up and dusting themselves down in the face of adversity.
    The Long Way to a Small, Angry Planet, the first book in the series, details the adventures of the crew of the ship Wayfarer. As the title suggests, it is much more about the journey than the destination. In a way, not a lot happens, but all the characters are changed by their interactions with one another.
    My favourite character in the book is the charming and tragic Dr Chef (yes, he is the ship’s doctor and chef), one of the last of an alien species called Grum, which resemble a kind of six-limbed otter and gradually change biological sex over their lifetime.
    This is just one example of the incredibly diverse cast of aliens that populate the Wayfarers books, which share a universe but mostly stand alone. There are Aeluons, who communicate by flashing colours on their faces, and the reptilian Aandrisk, whose society is influenced by the fact they lay eggs – children are normally the result of casual sex, and aren’t reared by their biological parents.
    There are also artificial intelligences that run ships and other hardware, but it is illegal to upload an AI to a humanoid robot. This is key in the second book, A Closed and Common Orbit, which is a fantastic examination of identity and autonomy.
    Chambers’s latest, the novella A Psalm for the Wild-Built, takes place in a new continuity outside the Wayfarers universe, but shares much of its DNA. It is set on a moon called Panga where humans realised that their sprawling, oil-burning factories were unsustainable and set up a vast rewilding project. “It was a crazy split, if you thought about it: half the land for a single species, half for the hundreds of thousands of others,” writes Chambers. “Finding a limit they’d stick to was victory enough.” Around the same time, robots became sentient and withdrew to the new wilderness, with humans promising to leave them alone.
    The book is set some time after this Transition, and follows a tea monk, Sibling Dex, who goes from settlement to settlement as a travelling salesperson-slash-roaming therapist. Despite bringing joy and comfort to those visited, Dex is unsatisfied and heads out into the wilds, looking for a new purpose – eventually making contact with a robot, Mosscap, the first time humans and robots had met in centuries.
    The heart of the book is the relationship between the two and the way they support each other. It is a joyful experience and, as with all of Chambers’s books, I was left with a warm, fuzzy feeling inside.

    Jacob also recommends…
    TV
    Legends of Tomorrow
    This show about time-travelling superheroes embraces the joy of being silly, and it is now one of my favourites. A recent episode has them meet David Bowie in 1970s London and find Spartacus on a spaceship.
    Book
    Revenger
    Alistair Reynolds
    The first novel in a trilogy sees sisters Adrana and Fura Ness join the crew of the Revenger, led by the space pirate Captain Rackamore, for swashbuckling sci-fi.

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