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Category: cosmology – Page 101

A consensus has arisen in the astronomical community that familiar matter made of atoms is not the dominant form of matter in the Universe. Instead, an invisible form of matter, called dark matter, is thought to be far more prevalent. However, a small group of researchers deny the existence of dark matter, instead saying our understanding of how objects move is incomplete. A recent paper in the Monthly Notices of the Royal Astronomical Society seems to have ruled this out definitively.

Stars, planets, and galaxies move under the direction of the force of gravity, and Isaac Newton worked out the laws that govern that motion, which we now call Newtonian dynamics. However, despite the enormous success of Newtonian dynamics, this success is not universal. Indeed, when Newton’s equations are applied to certain astronomical phenomena, they do not make the correct predictions. One such example is the speed at which galaxies rotate. When astronomers measure the speed of stars in the periphery of a galaxy, they move faster than can be explained by accepted theory. Instead, the galaxies should fly apart.

The solution to this mystery favored by most scientists is that beyond the familiar stars and clouds of gas, our galaxy also hosts a large amount of invisible matter, called dark matter. This dark matter adds to the gravitational force holding the galaxy together. Thus, the evidence for dark matter is indirect. It has never been observed in the laboratory; yet its ability to explain the motion of galaxies is strong circumstantial evidence that it exists.

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Scientists identified 18 new Tidal Disruption Events (TDEs), instances where a nearby black hole violently tears apart a neighboring star.

The powerful gravitational force of the black holes rips apart the star in its vicinity, resulting in a substantial release of energy across the entire electromagnetic spectrum.

The new catalog of TDEs was found by combing through the archival data of the satellite telescope NEOWISE. The team identified infrared patterns associated with these intense, transient bursts using a novel algorithm.

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But after a few billion years, something fishy begins to occur. Instead of approaching zero, the expansion rate starts to decrease at a slower rate than one would expect, and a distant galaxy’s recession speed doesn’t drop in the same fashion anymore. Once the Universe reaches an age that’s 7.8 billion years after the Big Bang, things start to get weird: these distant galaxies stop slowing down in their recession entirely, and appear to “coast” in the sense that they move away from us at a constant speed from moment-to-moment, as though the expansion had stopped decelerating.

And then, as the Universe continues to age, the recession speeds no longer remain constant, nor do they go back to decreasing. Instead, these distant galaxies appear to recede from us (and one another) more and more quickly. It’s as though some effect is causing the expansion to neither decelerate nor remain constant, but to actually increase and accelerate!

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Black holes are powerful gravitational engines. So you might imagine that there must be a way to extract energy from them given the chance, and you’d be right.

Certainly, we could tap into all the heat and kinetic energy of a black hole’s accretion disk and jets, but even if all you had was a black hole in empty space, you could still extract energy from a trick known as the Penrose process.

First proposed by Roger Penrose in 1971, it is a way to extract rotational energy from a black hole. It uses an effect known as frame dragging, where a rotating body twists nearby space in such a way that an object falling toward the body is dragged slightly along the path of rotation.

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“The memory requirements for PRIYA simulations are so big you cannot put them on anything other than a supercomputer,” Bird said.

TACC awarded Bird a Leadership Resource Allocation on the Frontera supercomputer. Additionally, analysis computations were performed using the resources of the UC Riverside High-Performance Computer Cluster.

The PRIYA simulations on Frontera are some of the largest cosmological simulations yet made, needing over 100,000 core-hours to simulate a system of 30723 (about 29 billion) particles in a ‘box’ 120 megaparsecs on edge, or about 3.91 million light-years across. PRIYA simulations consumed over 600,000 node hours on Frontera.

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MIT physicists have discovered a surprising twist in the Milky Way’s rotation curve that challenges our understanding of dark matter. By tracking the speed of stars across the galaxy, they’ve uncovered a potential deficit of dark matter at the galactic core.

Traditionally, astronomers believed that dark matter was responsible for the galaxy’s rotation. Still, the new analysis raises the possibility that the Milky Way’s gravitational center may be lighter in mass than previously thought.

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In this article, we argue that we can explain quantum stabilization of Morris-Thorne traversable wormholes through quantum mechanics. We suggest that the utilization of dark matter and dark energy, conceptualized as negative mass and negative energy tied to the universe’s information content, can stabilize these wormholes. This approach diverges from the original Morris-Thorne model by incorporating quantum effects, offering a credible and adequate source of the exotic matter needed to prevent wormhole collapse. We reassess the wormholes’ stability and information content considering the new calculated revised vacuum energy based on the mass of bit of information. This new calculation makes the wormholes more viable within our universe’s limits.

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