Do Merging Dwarf Galaxies Explain a Peculiar Gravitational-Wave Detection?
May 5, 2021•
Physics 14, s52
The hard-to-explain masses of two coalescing black holes could be accounted for if they were the central black holes in two distant, tiny galaxies that merged.
A. Palmese/Fermilab
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On May 21, 2019, the LIGO and Virgo collaborations recorded an unexpected gravitational-wave detection. The signal, designated GW190521, emanated from the coalescence of two black holes whose masses fall into a range that’s forbidden by conventional stellar evolution theories (see Viewpoint: A Heavyweight Merger). Now, Antonella Palmese, at Fermi National Accelerator Laboratory (Fermilab) and the University of Chicago, and Christopher Conselice, at the University of Manchester, UK, propose that the observation can be explained by the merger of the black holes at the centers of two low-mass dwarf galaxies [1]. Such “forbidden mass” black holes could form in dwarf galaxies fro
Linking Glaciers on Earth to the Climate on Mars
April 30, 2021•
Physics 14, 62
Geophysicist Jack Holt explains how Earth’s debris-covered glaciers can teach us about the climate history of Mars.
Jack Holt
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As a student, Jack Holt had three loves: geology, exploring remote mountain regions, and aviation. Now, as a geophysicist at the University of Arizona, he’s merged those loves into his academic pursuits. Holt has tracked the history of Earth’s magnetic field, which required visits to Death Valley in California, Baja California in Mexico, and the Big Island, Hawaii, and he ran an airborne field program to study the internal properties of glaciers, which took him to Antarctica. There, he used his postdoctoral experience in airborne radar sounding a geophysical technique based on long-wave echo reflections to map features buried beneath ice sheets.
Cubes Keep Their Distance
Physics 14, s42
Cubes suspended in a liquid are less likely than spheres to form clusters and fall out of solution.
A. Seyed-Ahmadi and A. Wachs [1]
A. Seyed-Ahmadi and A. Wachs [1]
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Particle-laden flows are ubiquitous in natural and industrial processes. Models that describe how particles behave in a suspension are vital for, among other things, explaining river deposits and designing waste-water treatment plants. But these models assume that particles are spherical, which is a problem in a world where sediment grains come in all shapes and sizes. Arman Seyed-Ahmadi and Anthony Wachs, of the University of British Columbia, Canada, now show through simulations that, unlike a sphere-laden flow, a cube-laden one tends to resist clustering, remaining homogeneous for longer. The finding provides an important update for models of environmental flows.
Counting All the Antistars in the Sky
April 20, 2021•
Physics 14, s50
Analyzing gamma-ray sources leads to an upper limit on how many antimatter stars could exist in the Milky Way.
S. Dupourqué/IRAP
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Nowadays it is taken for granted that the Universe contains no substantial amounts of antimatter. Most cosmological models include hypothetical physical processes to explain why matter dominates although the Universe should have been created with equal amounts of both. But in 2018, the Alpha Magnetic Spectrometer 2 (AMS-02) experiment on the International Space Station possibly detected several antihelium nuclei, suggesting that some original antimatter survived to form antistars and even antigalaxies. Now, Simon Dupourqué and colleagues at the Institut de Recherche en Astrophysique et Planétologie (IRAP), France, identify possible antistars based on ten years of gamma-ray observations from the orbiting Fermi Gamma-ray Space Telescope and derive constraints on how man
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