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Category: cosmology – Page 125

Objects in space reveal different aspects of their composition and behavior at different wavelengths of light. Supernova remnant Cassiopeia A (Cas A) is one of the most well-studied objects in the Milky Way across the wavelength spectrum. However, there are still secrets hidden within the star’s tattered remains.

The latest are being unlocked by one of the newest tools in the researchers’ toolbox, the James Webb Space Telescope—and Webb’s recent look in the near-infrared has blown researchers away.

Like a shiny, round ornament ready to be placed in the perfect spot on a holiday tree, supernova remnant Cassiopeia A (Cas A) gleams in a new image from NASA’s James Webb Space Telescope.

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A new analysis of the distribution of matter in the Universe continues to find a discrepancy in the clumpiness of dark matter in the late and early Universe, suggesting a fundamental error in the standard cosmological model.

Cosmologists study the Universe by making a vast range of observations using a variety of modern techniques. Each observation can reveal different details about the Universe’s composition over a certain period of its history. An astronomical survey—a map of a region of the sky—is a powerful way to scan a large swath of the Universe and the objects it contains. For example, a weak-lensing survey does that by obtaining sharp images of galaxies, which can then be used to map the distribution of the Universe’s matter throughout history. The Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) is one such weak-lensing survey, and it has the highest resolution and the deepest depth of all current weak-lensing surveys. Over the past six years, the HSC-SSP survey team has spent 330 nights scanning 3% of the entire spherical sky, capturing the light emitted by galaxies up to 10 billion years ago.

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The current measurements of the expansion rate of the universe are in disagreement, leading to a crisis in cosmology and the need for renewed research efforts into new physics and a new model of the universe.

Questions to inspire discussion.

What is the crisis in cosmology?
—The crisis in cosmology refers to the disagreement between measurements of the expansion rate of the universe, leading to the need for renewed research efforts into new physics and a new model of the universe.

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Study by the Universities of Bonn and St. Andrews proposes a new possible explanation for the Hubble tension.

The universe is expanding. How fast it does so is described by the so-called Hubble-Lemaitre constant. But there is a dispute about how big this constant actually is: Different measurement methods provide contradictory values. This so-called “Hubble tension” poses a puzzle for cosmologists. Researchers from the Universities of Bonn and St. Andrews are now proposing a new solution: Using an alternative theory of gravity, the discrepancy in the measured values can be easily explained — the Hubble tension disappears. The study has now been published in the Monthly Notices of the Royal Astronomical Society (MNRAS).

Understanding the Universe’s Expansion.

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A new theory suggests that the unification between quantum physics and general relativity has eluded scientists for 100 years because huge “fluctuations” in space and time mean that gravity won’t play by quantum rules.

Since the early 20th century, two revolutionary theories have defined our fundamental understanding of the physics that governs the universe. Quantum physics describes the physics of the small, at scales tinier than the atom, telling us how fundamental particles like electrons and photons interact and are governed. General relativity, on the other hand, describes the universe at tremendous scales, telling us how planets move around stars, how stars can die and collapse to birth black holes, and how galaxies cluster together to build the largest structures in the cosmos.

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A quantum property dubbed “magic” could be the key to explaining how space and time emerged, a new mathematical analysis by three RIKEN physicists suggests. The research is published in the journal Physical Review D.

It’s hard to conceive of anything more basic than the fabric of spacetime that underpins the universe, but have been questioning this assumption. “Physicists have long been fascinated about the possibility that space and time are not fundamental, but rather are derived from something deeper,” says Kanato Goto of the RIKEN Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS).

This notion received a boost in the 1990s, when theoretical physicist Juan Maldacena related the gravitational theory that governs spacetime to a theory involving . In particular, he imagined a hypothetical space—which can be pictured as being enclosed in something like an infinite soup can, or “bulk”—holding objects like that are acted on by gravity. Maldacena also imagined particles moving on the surface of the can, controlled by . He realized that mathematically a used to describe the particles on the boundary is equivalent to a gravitational theory describing the black holes and spacetime inside the bulk.

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A RIKEN physicist and two colleagues have found that a wormhole—a bridge connecting distant regions of the Universe—helps to shed light on the mystery of what happens to information about matter consumed by black holes.

Einstein’s theory of predicts that nothing that falls into a black hole can escape its clutches. But in the 1970s, Stephen Hawking calculated that black holes should emit radiation when , the theory governing the microscopic realm, is considered. “This is called black hole evaporation because the black hole shrinks, just like an evaporating water droplet,” explains Kanato Goto of the RIKEN Interdisciplinary Theoretical and Mathematical Sciences.

This, however, led to a paradox. Eventually, the black hole will evaporate entirely—and so too will any information about its swallowed contents. But this contradicts a fundamental dictum of quantum physics: that information cannot vanish from the Universe. “This suggests that general relativity and quantum mechanics as they currently stand are inconsistent with each other,” says Goto. “We have to find a unified framework for quantum gravity.”

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Black holes really are giant fuzzballs, a new study says.

The study attempts to put to rest the debate over Stephen Hawking’s famous information paradox, the problem created by Hawking’s conclusion that any data that enters a black hole can never leave. This conclusion accorded with the laws of thermodynamics, but opposed the fundamental laws of quantum mechanics.

“What we found from is that all the mass of a black hole is not getting sucked in to the center,” said Samir Mathur, lead author of the study and professor of physics at The Ohio State University. “The black hole tries to squeeze things to a point, but then the particles get stretched into these strings, and the strings start to stretch and expand and it becomes this fuzzball that expands to fill up the entirety of the black hole.”

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Black holes aren’t surrounded by a burning ring of fire after all, suggests new research.

Some physicists have believed in a “firewall” around the perimeter of a black hole that would incinerate anything sucked into its powerful gravitational pull.

But a team from The Ohio State University has calculated an explanation of what would happen if an electron fell into a typical black hole, with a mass as big as the sun.

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