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Category: cosmology

Across cosmic history, powerful forces have acted on matter, reshaping the universe into an increasingly complex web of structures. Now, new research led by Joshua Kim and Mathew Madhavacheril at the University of Pennsylvania and their collaborators at Lawrence Berkeley National Laboratory suggests our universe has become “messier and more complicated” over the roughly 13.8 billion years it’s been around, or rather, the distribution of matter over the years is less “clumpy” than it should be expected.

“Our work cross-correlated two types of datasets from complementary, but very distinct, surveys,” says Madhavacheril, “and what we found was that, for the most part, the story of structure formation is remarkably consistent with the predictions from Einstein’s gravity. We did see a hint for a small discrepancy in the amount of expected clumpiness in recent epochs, around four billion years ago, which could be interesting to pursue.”

The data, which was published in the Journal of Cosmology and Astroparticle Physics and the preprint server arXiv, comes from the Atacama Cosmology Telescope’s (ACT) final data release (DR6) and the Dark Energy Spectroscopic Instrument’s (DESI) Year 1.

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Cosmic Radiation: A Supernova’s Deadly Reach

Around 2.6 million years ago, a supernova erupted just 150 light-years from Earth, creating a dazzling display in the sky. But its most significant impact may have occurred years later when a wave of cosmic radiation reached Earth, triggering a marine extinction event. Researchers led by Adrian Melott of the University of Kansas propose that this cosmic catastrophe may have contributed to the disappearance of marine giants, including the Megalodon. Their findings were published in Astrobiology.

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The story of collapsing stars is often said to go from neutron stars directly to black holes, but there could be a number of intermediate steps where the structure of matter becomes one of quark soup. In this talk we take a look at the theory and the possibly evidence for such Quark stars — and compare them with the most dangerousmaterial thought possible — the strangelet.

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Pinpointing a Milepost Marker Star that Opened the Realm of Galaxies At the dawn of the 20th century, astronomers faced a cosmic puzzle. The night sky was dotted with more than 100 nebulous objects cataloged in the late 1700s by French astronomer Charles Messier. Most were identified as star clusters, nebulae, supernova remnants, or glowing clouds of gas.

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High-Speed Cosmic Kick: A New Black Hole Discovery

A newly formed black hole recently received a high-speed “kick,” thanks to gravitational waves, which propelled it at about 5 million kilometers per hour—roughly 200 times the speed of light. This surprising discovery was made through data collected by gravitational wave observatories LIGO and Virgo. These observatories detected spacetime ripples produced by the coalescence of two black holes on January 29, 2020, revealing the large recoil effect.

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For the first time, scientists have measured the early universe running in extreme slow motion, showing that time was five times slower just a billion years after the Big Bang. By studying nearly 200 quasars – hyperactive supermassive black holes at the centers of ancient galaxies – researchers have provided new evidence for Einstein’s theory of general relativity regarding an expanding universe.

The Mystery of Early Universe Time Dilation

Einstein’s general theory of relativity predicts that, as the universe expands, distant objects (and therefore the early universe) should appear to experience slower time. However, directly observing this has been challenging due to the vast distances and the faint signals coming from early cosmic phenomena. Previous research had established this dilation back to half the age of the universe using supernovae, but quasars have now pushed this further back to just a tenth of the universe’s age.

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Fast radio bursts (FRBs) are short blasts of radio waves whose origins remain a mystery. A new theoretical study explores a possible source in the atmospheres around highly magnetized neutron stars called magnetars [1]. Using numerical simulations, the researchers show that magnetar atmospheres can host powerful shock waves—or “monster shocks”—that produce gigahertz-frequency emissions, consistent with FRB observations.

The first reported observation of an FRB was in 2007, and since then astronomers have collected over a thousand bursts from across the sky. They seem to be connected to compact objects—such as neutron stars or black holes—located at large distances from Earth. “We know that they are cosmological, but their origin and production mechanism remain elusive,” says Arno Vanthieghem from Sorbonne University and the Paris Observatory. He and Amir Levinson from Tel Aviv University, Israel, have explored a possible connection between FRBs and magnetically driven shocks around magnetars.

Previous work has looked at FRB-producing mechanisms around magnetars, but Vanthieghem and Levinson are the first to explore shock-induced radio emission in the inner magnetosphere—the strong-magnetic-field region surrounding a magnetar. The researchers showed that a disturbance, such as a starquake occurring on the magnetar surface, can cause a magnetic-field wave to travel outward through the charged particles in the magnetosphere. They found that this wave can be amplified into a monster shock in which charged particles reach highly relativistic speeds. These particles emit a burst of radio waves that could be seen as an FRB by a distant observer. Vanthieghem says that future observations might be able to provide evidence for this mechanism by pinpointing the location of FRB emission within a magnetar’s environment.

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PRESS RELEASE — Today, the U.S. Department of Energy (DOE) announced $71 million in funding for 25 projects in high energy physics that will use the emerging technologies of quantum information science to answer fundamental questions about the universe.

This research will develop and deploy innovative solutions for scientific discovery by applying the unique capabilities and features of the quantum world to the challenges of making new discoveries in fundamental physics. Awards funded under this program will advance theories of gravity and spacetime, develop quantum sensors that can see previously undetectable signals, and build pathfinder experiments to demonstrate increased discovery reach in searches for dark matter and other new particles and phenomena.

“Quantum information science is opening up new ways for us to understand and explore the universe,” said Regina Rameika, DOE Associate Director of Science for High Energy Physics. “With these projects, we are supporting scientists in developing quantum technologies that will empower the next generation of theory and experiment in high energy physics.”

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Astrophysicists have long been intrigued by the possibility of dark stars-massive celestial objects fueled not by nuclear fusion but by the enigmatic energy of dark matter. Thanks to images taken by the James Webb Space Telescope (JWST), the scientific community has perhaps also found signs of such elusive entities. Could these dark stars, which shine billions of times brighter than our sun, rewrite the story of the universe’s infancy?

Dark stars, despite the word “dark”, are hypothesized luminous sources that may have existed in the universe’s infancy. In contrast to traditional stars that work with nuclear fusion, dark stars are speculated to obtain their energy from self-annihilation of dark matter particles.

As a result, energy is released that warms the ambient hydrogen and helium, and this leads the primordial clouds to glow brightly and expand to enormous scale-some up to a million times mass of the sun. These stars may have also been born in “minihaloes”, dense pockets of dark matter in the early universe.

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