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  • richardmitnick 1:39 pm on April 15, 2020 Permalink | Reply
    Tags: "First of its kind experiment uses diamond anvils to simulate the Earth's core", , , It has long been known that at the heart of the Earth lies a solid core surrounded by a less dense liquid outer core., , Researchers successfully determined the density of liquid iron and the speed at which sound propagates through it at extremely high pressures., The density of the Earth's outer core appears to be about 8% less dense than pure liquid iron., They achieved this with use of a highly specialized diamond anvil that compresses samples and sophisticated X-ray measurements., University of Tokyo,   

    From University of Tokyo via phys.org: “First of its kind experiment uses diamond anvils to simulate the Earth’s core” 

    From University of Tokyo

    via


    phys.org

    April 15, 2020

    1
    The diamond anvil used to compress an iron sample. Credit: © 2020 Kuwayama et al.

    In an effort to investigate conditions found at the Earth’s molten outer core, researchers successfully determined the density of liquid iron and the speed at which sound propagates through it at extremely high pressures. They achieved this with use of a highly specialized diamond anvil that compresses samples, and sophisticated X-ray measurements. Their findings confirm the molten outer core is less dense than liquid iron, and also put values on the discrepancy.

    Jules Verne’s 1864 novel “Journey to the Center of the Earth” depicts explorers on an imaginative trip to the Earth’s core where they find a gargantuan hollow cavern hosting a prehistoric environment populated with dinosaurs. They get there thanks to a tank-like drilling machine that navigates through volcanoes. It sounds fun, but needless to say, it’s a far cry from reality, where researchers explore the inner Earth with a range of techniques and instruments from the comparative safety of the Earth’s surface.

    Seismic equipment that measures how earthquakes travel through the planet are pivotal to map some of the larger structural arrangements within the Earth, and thanks to this, it has long been known that at the heart of the Earth lies a solid core surrounded by a less dense liquid outer core. For the first time, experiments and simulations have shown researchers details about this outer core that were previously unobtainable. And these studies reveal some fascinating details.

    “Recreating conditions found at the center of the Earth up here on the surface is not easy,” said Project Assistant Professor Yasuhiro Kuwayama from the Department of Earth and Planetary Science. “We used a diamond anvil to compress a sample of liquid iron subject to intense heat. But more than just creating the conditions, we needed to maintain them long enough to take our measurements. This was the real challenge.”

    2
    Different layers within the Earth have differing compositions and densities. Credit: © 2020 Kelvinsong – CC BY-SA 3.0

    It is harder to measure the density of a liquid sample than a solid one, as it takes the apparatus longer to do so. But with a unique experimental set-up centered on a diamond anvil, which was crafted over two decades, Kuwayama and his team maintained their sample sufficiently to collect the data they required. They used a highly focused X-ray source from the SPring-8 synchrotron in Japan to probe the sample and measure its density.

    SPring-8 synchrotron, located in Hyōgo Prefecture, Japan

    “We found the density of liquid iron such as you’d find in the outer core to be about 10 tons per cubic meter at a pressure of 116 gigapascals, and the temperature to be 4,350 Kelvin,” explained Kuwayama. “For reference, typical room temperature is about 273 Kelvin. So this sample is over 16 times hotter than your room, and 10 times denser than water.”

    When compared to this new measurement, the density of the Earth’s outer core appears to be about 8% less dense than pure liquid iron. The suggestion here is that there are additional lighter elements in the molten outer core that are currently unidentified. This research could aid others in their quest to reveal more unobtainable secrets from deep within the Earth.

    “It’s important to investigate these things to understand more, not only about the Earth’s core, but about the composition, and thus behavior, of other planets as well,” concluded Kuwayama. “It’s important to note that it was not just elaborate equipment that helped us find this new information, but also meticulous mathematical modeling and analytical methods. We were pleasantly surprised by how effective this approach was, and hope it can lead to a greater understanding of the world beneath our feet.”

    The study is published in Physical Review Letters.

    See the full article here .

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    The University of Tokyo aims to be a world-class platform for research and education, contributing to human knowledge in partnership with other leading global universities. The University of Tokyo aims to nurture global leaders with a strong sense of public responsibility and a pioneering spirit, possessing both deep specialism and broad knowledge. The University of Tokyo aims to expand the boundaries of human knowledge in partnership with society. Details about how the University is carrying out this mission can be found in the University of Tokyo Charter and the Action Plans.

     
  • richardmitnick 1:49 pm on March 3, 2020 Permalink | Reply
    Tags: "The Hyper-Kamiokande project is officially approved.", , , Hyper-Kamiokande is designed to elucidate the origin of matter and the Grand Unified Theory of elementary particles., International contributions will also include data acquisition system; water system upgrade; detector calibration systems; and downstream offline computing system., International contributions will include the near/intermediate detector complex., International contributions will include the rest of photosensors for the inner detector; sensor covers and light collectors; photosensors for the outer detector; and readout electronics., J-PARC accelerator upgrade, , , University of Tokyo   

    From University of Tokyo: “The Hyper-Kamiokande project is officially approved.” 

    From University of Tokyo

    12/February/2020

    Hyper-Kamiokande, a neutrino physics laboratory to be located underground in the Mozumi Mine of the Kamioka Mining and Smelting Co. near the Kamioka section of the city of Hida in Gifu Prefecture, Japan.

    Hyper-Kamiokande (HK or Hyper-K) project is the world-leading international scientific research project hosted by Japan aiming to elucidate the origin of matter and the Grand Unified Theory of elementary particles. The project consists of the Hyper-K detector, which has an 8.4 times larger fiducial mass than its predecessor, Super-Kamiokande, equipped with newly developed high-sensitivity photosensors and a high-intensity neutrino beam produced by an upgraded J-PARC accelerator facility.

    J-PARC Facility Japan Proton Accelerator Research Complex , located in Tokai village, Ibaraki prefecture, on the east coast of Japan.

    The supplementary budget for FY2019 which includes the first-year construction budget of 3.5 billion yen for the Hyper-Kamiokande project was approved by the Japanese Diet. The Hyper-K project has officially started. The operations will begin in 2027.

    The overall Japanese contribution will include the cavern excavation, construction of the tank (water container) and its structure, half of the photosensors for the inner detector, main part of the water system, Tier 0 offline computing, together with J-PARC accelerator upgrade and construction of a new experimental facility for the near detector complex. International contributions will include the rest of photosensors for the inner detector, sensor covers and light collectors, photosensors for the outer detector, readout electronics, data acquisition system, water system upgrade, detector calibration systems, downstream offline computing system, and the near/intermediate detector complex.

    We would like to work together with domestic and international colleagues in Hyper-K for the development of neutrino physics and astrophysics.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    The University of Tokyo aims to be a world-class platform for research and education, contributing to human knowledge in partnership with other leading global universities. The University of Tokyo aims to nurture global leaders with a strong sense of public responsibility and a pioneering spirit, possessing both deep specialism and broad knowledge. The University of Tokyo aims to expand the boundaries of human knowledge in partnership with society. Details about how the University is carrying out this mission can be found in the University of Tokyo Charter and the Action Plans.

     
  • richardmitnick 11:37 am on January 11, 2020 Permalink | Reply
    Tags: "On the hunt for primordial black holes", , , , , , University of Tokyo   

    From University of Tokyo via phys.org: “On the hunt for primordial black holes” 

    From University of Tokyo

    via


    From phys.org

    January 10, 2020
    Motoko Kakubayashi, University of Tokyo

    1
    The Andromeda Galaxy is the Milky Way’s closest neighbour galaxy, 2.5 million light years away. Credit: HSC Project / NAOJ

    The theory that dark matter could be made of primordial black holes a fraction of a millimeter in size has been ruled out by a team of researchers led by the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU).

    In 1974, physicist Stephen Hawking described how primordial black holes could have formed in the fraction of a second after the Big Bang. Primordial black holes could have masses ranging from a tiny speck to 100,000 times our sun. In contrast, supermassive black holes detected by astronomical observations started forming at least hundreds of thousands of years later, and are millions or billions times larger than our sun. Since primordial black holes of any size have not been detected, they have been an intriguing candidate for elusive dark matter.

    As far as we currently know, baryonic matter only makes up 5 percent of all matter in the universe. The rest is either dark matter (27 percent) or dark energy (68 percent), both of which have not yet been physically detected. But researchers are confident that dark matter exists because we can see its effect on our universe. Without the gravitational force from dark matter, the stars in our Milky Way Galaxy would be flying apart.

    To test the theory that primordial black holes, specifically those about the mass of the moon or less, could be dark matter, Kavli IPMU researchers Masahiro Takada, Naoki Yasuda, Hiroko Niikura and collaborators from Japan, India and the U.S. searched for these tiny black holes between Earth and the Andromeda Galaxy, the Milky Way’s closest neighbor galaxy, 2.5 million light years away.

    2
    Data from the star which showed characteristics of being magnified by a potential gravitational lens, possibly by a primordial black hole. About 4 hours after data taking on the Subaru Telescope began, one star began to shine brighter. Less than an hour later, the star reached peak brightness before becoming dimmer. (From left to right) the original image, the brightened image, the differential image and the residual image. Niikura et al.

    “What made me interested in this project was the tremendous impact it would have on uncovering the nature of dark matter,” says Niikura. “Discovering primordial black holes would be a historical achievement. Even a negative result would be valuable information for researchers piecing together the scenario of how the universe began.”

    To look for black holes, the team used the gravitational lensing effect.

    Gravitational Lensing NASA/ESA

    Gravitational lenses were first explained by Albert Einstein, who said it was possible for an image of a distant object, such as a star, to become distorted due to the gravitational effect of a massive object between the star and Earth. The massive object’s gravity could act like a magnifying glass lens, bending the star’s light and making it appear brighter or distorted to human observers on Earth.

    Because a star, a black hole and the Earth are constantly moving in interstellar space, a star would gradually grow brighter, then dimmer to observers on Earth, as it moves across the path of a gravitational lens. So the researchers captured 190 consecutive images of the entire Andromeda Galaxy, thanks to the Hyper Suprime-Cam digital camera on the Subaru Telescope in Hawaii.

    NAOJ Subaru Hyper Suprime-Cam

    NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA,4,207 m (13,802 ft) above sea level

    If dark matter is made of primordial black holes and, in this case, ones lighter than the moon, the researchers expected to find 1,000 gravitational microlenses. They calculated this estimate by assuming dark matter in the entire galaxy’s halo is made up of primordial black holes, and taking into consideration the number of stars in the Andromeda Galaxy that could be affected by a primordial black hole, and finally the chances of their equipment capturing a gravitational microlens event.

    Gravitational microlensing, S. Liebes, Physical Review B, 133 (1964): 835

    The telescope photographed 90 million stars. It took two years for the team to filter out all of the noise and non-gravitational lens events from the data. In the end, they could only identify one star that brightened then dimmed—suggesting a possible primordial black hole—meaning it is unlikely that they make up all of dark matter.

    Even so, Niikura explains that there is still a lot to learn about primordial black holes. The researchers had only debunked the theory for a specific mass: black holes with a mass similar to or less than the moon. Previous studies have ruled out other masses, or to what extent they could account for dark matter. But there is still a chance that primordial black holes of varying sizes might be out there. The analytical approach developed by the Kavli team could be used in future primordial black hole studies, including trying to determine if black holes discovered by the Laser Interferometer Gravitational Wave-Observatory (LIGO) in the U.S. could in fact be primordial.

    MIT /Caltech Advanced aLigo


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Science paper:
    Microlensing constraints on primordial black holes with Subaru/HSC Andromeda observations
    Nature Astronomy

    See the full article here .

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    About Science X in 100 words

    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
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    The University of Tokyo aims to be a world-class platform for research and education, contributing to human knowledge in partnership with other leading global universities. The University of Tokyo aims to nurture global leaders with a strong sense of public responsibility and a pioneering spirit, possessing both deep specialism and broad knowledge. The University of Tokyo aims to expand the boundaries of human knowledge in partnership with society. Details about how the University is carrying out this mission can be found in the University of Tokyo Charter and the Action Plans.

     
  • richardmitnick 1:44 pm on April 27, 2018 Permalink | Reply
    Tags: , , Majorana fermion science, , , , , , Topological quantum computation, University of Tokyo   

    From Physics Illinois: “Topological insulator �flips� for superconductivity” 

    U Illinois bloc

    Physics Illinois

    U Illinois Physics bloc

    4/27/2018
    Siv Schwink

    Topology meets superconductivity through innovative reverse-order sample preparation.

    1
    (L-R) Professor of Physics James Eckstein, his graduate student Yang Bai, and Professor of Physics Tai-Chang Chiang pose in front of the atomic layer by layer molecular beam epitaxy system used to grow the topological insulator thin-film samples for this study, in the Eckstein laboratory at the University of Illinois. Photo by L. Brian Stauffer, University of Illinois at Urbana-Champaign.

    A groundbreaking sample preparation technique has enabled researchers at the University of Illinois at Urbana-Champaign and the University of Tokyo to perform the most controlled and sensitive study to date of a topological insulator (TI) closely coupled to a superconductor (SC). The scientists observed the superconducting proximity effect—induced superconductivity in the TI due to its proximity to the SC—and measured its relationship to temperature and the thickness of the TI.

    TIs with induced superconductivity are of paramount interest to physicists because they have the potential to host exotic physical phenomena, including the elusive Majorana fermion—an elementary particle theorized to be its own antiparticle—and to exhibit supersymmetry—a phenomenon reaching beyond the standard model that would shed light on many outstanding problems in physics. Superconducting TIs also hold tremendous promise for technological applications, including topological quantum computation and spintronics.

    Naturally occurring topological superconductors are rare, and those that have been investigated have exhibited extremely small superconducting gaps and very low transition temperatures, limiting their usefulness for uncovering the interesting physical properties and behaviors that have been theorized.

    TIs have been used in engineering superconducting topological superconductors (TI/SC), by growing TIs on a superconducting substrate. Since their experimental discovery in 2007, TIs have intrigued condensed matter physicists, and a flurry of theoretical and experimental research taking place around the globe has explored the quantum-mechanical properties of this extraordinary class of materials. These 2D and 3D materials are insulating in their bulk, but conduct electricity on their edges or outer surfaces via special surface electronic states which are topologically protected, meaning they can’t be easily destroyed by impurities or imperfections in the material.

    But engineering such TI/SC systems via growing TI thin films on superconducting substrates has also proven challenging, given several obstacles, including lattice structure mismatch, chemical reactions and structural defects at the interface, and other as-yet poorly understood factors.

    2
    The �flip-chip� cleavage-based sample preparation: (A) A photo and a schematic diagram of assembled Bi2Se3(0001)/Nb sample structure before cleavage. (B) Same sample structure after cleavage exposing a �fresh� surface of the Bi2Se3 film with a pre-determined thickness. Image courtesy of James Eckstein and Tai-Chang-Chiang, U. of I. Department of Physics and Frederick Seitz Materials Research Laboratory.

    Now, a novel sample-growing technique developed at the U. of I. has overcome these obstacles. Developed by physics professor James Eckstein in collaboration with physics professor Tai-Chang Chiang, the new “flip-chip” TI/SC sample-growing technique allowed the scientists to produce layered thin-films of the well-studied TI bismuth selenide on top of the prototypical SC niobium—despite their incompatible crystalline lattice structures and the highly reactive nature of niobium.

    These two materials taken together are ideal for probing fundamental aspects of the TI/SC physics, according to Chiang: “This is arguably the simplest example of a TI/SC in terms of the electronic and chemical structures. And the SC we used has the highest transition temperature among all elements in the periodic table, which makes the physics more accessible. This is really ideal; it provides a simpler, more accessible basis for exploring the basics of topological superconductivity,” Chiang comments.

    The method allows for very precise control over sample thickness, and the scientists looked at a range of 3 to 10 TI layers, with 5 atomic layers per TI layer. The team’s measurements showed that the proximity effect induces superconductivity into both the bulk states and the topological surface states of the TI films. Chiang stresses, what they saw gives new insights into superconducting pairing of the spin-polarized topological surface states.

    “The results of this research are unambiguous. We see the signal clearly,” Chiang sums up. “We investigated the superconducting gap as a function of TI film thickness and also as a function of temperature. The results are pretty simple: the gap disappears as you go above niobium’s transition temperature. That’s good—it’s simple. It shows the physics works. More interesting is the dependence on the thickness of the film. Not surprisingly, we see the superconducting gap reduces for increasing TI film thickness, but the reduction is surprisingly slow. This observation raises an intriguing question regarding how the pairing at the film surface is induced by coupling at the interface.”

    Chiang credits Eckstein with developing the ingenious sample preparation method. It involves assembling the sample in reverse order, on top of a sacrificial substrate of aluminum oxide, commonly known as the mineral sapphire. The scientists are able to control the specific number of layers of TI crystals grown, each of quintuple atomic thickness. Then a polycrystalline superconducting layer of niobium is sputter-deposited on top of the TI film. The sample is then flipped over and the sacrificial layer that had served as the substrate is dislodged by striking a “cleavage pin.” The layers are cleaved precisely at the interface of the TI and aluminum oxide.

    3
    A close-up shot of the atomic layer by layer molecular beam epitaxy system used to grow the topological insulator thin-film samples for this study, located in the Eckstein laboratory at the University of Illinois. Photo by L. Brian Stauffer, University of Illinois at Urbana-Champaign.

    Eckstein explains, “The ‘flip-chip’ technique works because the layers aren’t strongly bonded—they are like a stack of paper, where there is strength in the stack, but you can pull apart the layers easily. Here, we have a triangular lattice of atoms, which comes in packages of five—these layers are strongly bonded. The next five layers sit on top, but are weakly bonded to the first five. It turns out, the weakest link is right at the substrate-TI interface. When cleaved, this method gives a pure surface, with no contamination from air exposure.”

    The cleavage was performed in an ultrahigh vacuum, within a highly sensitive instrument at the Institute for Solid State Physics at the University of Tokyo capable of angle-resolved photoemission spectroscopy (ARPES) at a range of temperatures.

    Chiang acknowledges, “The superconducting features occur at very small energy scales—it requires a very high energy resolution and very low temperatures. This portion of the experiment was completed by our colleagues in the University of Tokyo, where they have the instruments with the sensitivity to get the resolution we need for this kind of study. We couldn’t have done this without this international collaboration.”

    “This new sample preparation method opens up many new avenues in research, in terms of exotic physics, and, in the long term, in terms of possible useful applications—potentially even including building a better superconductor. It will allow preparation of samples using a wide range of other TIs and SCs. It could also be useful in miniaturization of electronic devices, and in spintronic computing, which would require less energy in terms of heat dissipation,” Chiang concludes.

    Eckstein adds, “There is a lot of excitement about this. If we can make a superconducting TI, theoretical predictions tell us that we could find a new elementary excitation that would make an ideal topological quantum bit, or qubit. We’re not there yet, and there are still many things to worry about. But it would be a qubit whose quantum mechanical wave function would be less susceptible to local perturbations that might cause dephasing, messing up calculations.”

    These findings were published online on 27 April 2018 in the journal Science Advances.

    See the full article here .

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    The University of Illinois at Urbana-Champaign community of students, scholars, and alumni is changing the world.

    With our land-grant heritage as a foundation, we pioneer innovative research that tackles global problems and expands the human experience. Our transformative learning experiences, in and out of the classroom, are designed to produce alumni who desire to make a significant, societal impact.

     
  • richardmitnick 8:20 am on October 2, 2017 Permalink | Reply
    Tags: , , , , , , Kyoto University, , , University of Tübingen, , University of Tokyo   

    From Science: “Sloshing, supersonic gas may have built the baby universe’s biggest black holes” 

    AAAS
    Science

    Sep. 28, 2017
    Joshua Sokol

    1
    Supermassive black holes a billion times heavier than the sun are too big to have formed conventionally. NASA Goddard Space Flight Center

    A central mystery surrounds the supermassive black holes that haunt the cores of galaxies: How did they get so big so fast? Now, a new, computer simulation–based study suggests that these giants were formed and fed by massive clouds of gas sloshing around in the aftermath of the big bang.

    “This really is a new pathway,” says Volker Bromm, an astrophysicist at the University of Texas in Austin who was not part of the research team. “But it’s not … the one and only pathway.”

    Astronomers know that, when the universe was just a billion years old, some supermassive black holes were already a billion times heavier than the sun. That’s much too big for them to have been built up through the slow mergers of small black holes formed in the conventional way, from collapsed stars a few dozen times the mass of the sun. Instead, the prevailing idea is that these behemoths had a head start. They could have condensed directly out of seed clouds of hydrogen gas weighing tens of thousands of solar masses, and grown from there by gravitationally swallowing up more gas. But the list of plausible ways for these “direct-collapse” scenarios to happen is short, and each option requires a perfect storm of circumstances.

    For theorists tinkering with computer models, the trouble lies in getting a massive amount of gas to pile up long enough to collapse all at once, into a vortex that feeds a nascent black hole like water down a sink drain. If any parts of the gas cloud cool down or clump up early, they will fragment and coalesce into stars instead. Once formed, radiation from the stars would blow away the rest of the gas cloud.

    2
    Computer models show how supersonic streams of gas coalesce around nuggets of dark matter—forming the seed of a supermassive black hole. Shingo Hirano

    One option, pioneered by Bromm and others, is to bathe a gas cloud in ultraviolet light, perhaps from stars in a next-door galaxy, and keep it warm enough to resist clumping. But having a galaxy close enough to provide that service would be quite the coincidence.

    The new study proposes a different origin. Both the early universe and the current one are composed of familiar matter like hydrogen, plus unseen clumps of dark matter.

    Dark Matter Research

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    Dark Matter Particle Explorer China

    DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB deep in Sudbury’s Creighton Mine

    LUX Dark matter Experiment at SURF, Lead, SD, USA

    ADMX Axion Dark Matter Experiment, U Uashington

    Today, these two components move in sync. But very early on, normal matter may have sloshed back and forth at supersonic speeds across a skeleton provided by colder, more sluggish dark matter. In the study, published today in Science, simulations show that where these surges were strong, and crossed the path of heavy clumps of dark matter, the gas resisted premature collapse into stars and instead flowed into the seed of a supermassive black hole. These scenarios would be rare, but would still roughly match the number of supermassive black holes seen today, says Shingo Hirano, an astrophysicist at the University of Texas and lead author of the study.

    Priya Natarajan, an astrophysicist at Yale University, says the new simulation represents important computational progress. But because it would have taken place at a very distant, early moment in the history of the universe, it will be difficult to verify. “I think the mechanism itself in detail is not going to be testable,” she says. “We will never see the gas actually sloshing and falling in.”

    But Bromm is more optimistic, especially if such direct-collapse black hole seeds also formed slightly later in the history of the universe. He, Natarajan, and other astronomers have been looking for these kinds baby black holes, hoping to confirm that they do, indeed, exist and then trying to work out their origins from the downstream consequences.

    In 2016, they found several candidates, which seem to have formed through direct collapse and are now accreting matter from clouds of gas. And earlier this year, astronomers showed that the early, distant universe is missing the glow of x-ray light that would be expected from a multitude of small black holes—another sign favoring the sudden birth of big seeds that go on to be supermassive black holes. Bromm is hopeful that upcoming observations will provide more definite evidence, along with opportunities to evaluate the different origin theories. “We have these predictions, we have the signatures, and then we see what we find,” he says. “So the game is on.”

    See the full article here .

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