May 3, 2022 03:46 PM
(This post was last modified: May 3, 2022 03:47 PM by C C.)
The universe could stop expanding 'remarkably soon', study suggests
https://www.livescience.com/end-cosmic-expansion
INTRO: After nearly 13.8 billion years of nonstop expansion, the universe could soon grind to a standstill, then slowly start to contract, new research published in the journal Proceedings of the National Academy of Sciences suggests.
In the new paper, three scientists attempt to model the nature of dark energy — a mysterious force that seems to be causing the universe to expand ever faster — based on past observations of cosmic expansion. In the team's model, dark energy is not a constant force of nature, but an entity called quintessence, which can decay over time.
The researchers found that, even though the expansion of the universe has been accelerating for billions of years, the repellent force of dark energy may be weakening. According to their model, the acceleration of the universe could rapidly end within the next 65 million years — then, within 100 million years, the universe could stop expanding altogether, and instead it could enter an era of slow contraction that ends billions of years from now with the death — or perhaps the rebirth — of time and space.
And this could all happen "remarkably" quickly, said study co-author Paul Steinhardt, Director of the Princeton Center for Theoretical Science at Princeton University in New Jersey.
"Going back in time 65 million years, that's when the Chicxulub asteroid hit the Earth and eliminated the dinosaurs," Steinhardt told Live Science. "On a cosmic scale, 65 million years is remarkably short."
Nothing about this theory is controversial or implausible, Gary Hinshaw, a professor of physics and astronomy at the University of British Columbia who was not involved in the study, told Live Science. However, because the model hinges on past observations of expansion alone — and because the present nature of dark energy in the universe is such a mystery — the predictions in this paper are currently impossible to test. For now, they can only remain theories... (MORE - details)
A Mysterious Signal from the Center of the Galaxy May Have Just Been Explained
https://www.vice.com/en/article/xgdjed/a...-explained
INTRO: For more than a decade, astronomers have been puzzled by an unexplained surplus of gamma ray signals—the highest energy form of light—that originate at the center of our galaxy, the Milky Way. Known as the Galactic Center Excess (GCE), this diffuse glow has prompted many exciting hypotheses, including the idea that it may be driven by collisions between particles of dark matter, an enigmatic substance that makes up most of the mass in the universe.
Now, scientists led by Anuj Gautam, a Masters student at the Australian National University, have presented new evidence that the GCE is powered by a population of rapidly spinning dead stars, known as millisecond pulsars, that are individually invisible, but could together produce the strange gamma-ray glow, which stretches for about 5,000 light years in every direction around the galactic center.
The team suggests that these extreme stellar corpses could “naturally reproduce the morphology, spectral shape and intensity of the GCE signal” and, “as a bonus,” may also be responsible for a “mysterious microwave ‘haze’ from the inner galaxy,” according to a study published on Thursday in Nature Astronomy... (MORE - details)
https://www.livescience.com/end-cosmic-expansion
INTRO: After nearly 13.8 billion years of nonstop expansion, the universe could soon grind to a standstill, then slowly start to contract, new research published in the journal Proceedings of the National Academy of Sciences suggests.
In the new paper, three scientists attempt to model the nature of dark energy — a mysterious force that seems to be causing the universe to expand ever faster — based on past observations of cosmic expansion. In the team's model, dark energy is not a constant force of nature, but an entity called quintessence, which can decay over time.
The researchers found that, even though the expansion of the universe has been accelerating for billions of years, the repellent force of dark energy may be weakening. According to their model, the acceleration of the universe could rapidly end within the next 65 million years — then, within 100 million years, the universe could stop expanding altogether, and instead it could enter an era of slow contraction that ends billions of years from now with the death — or perhaps the rebirth — of time and space.
And this could all happen "remarkably" quickly, said study co-author Paul Steinhardt, Director of the Princeton Center for Theoretical Science at Princeton University in New Jersey.
"Going back in time 65 million years, that's when the Chicxulub asteroid hit the Earth and eliminated the dinosaurs," Steinhardt told Live Science. "On a cosmic scale, 65 million years is remarkably short."
Nothing about this theory is controversial or implausible, Gary Hinshaw, a professor of physics and astronomy at the University of British Columbia who was not involved in the study, told Live Science. However, because the model hinges on past observations of expansion alone — and because the present nature of dark energy in the universe is such a mystery — the predictions in this paper are currently impossible to test. For now, they can only remain theories... (MORE - details)
A Mysterious Signal from the Center of the Galaxy May Have Just Been Explained
https://www.vice.com/en/article/xgdjed/a...-explained
INTRO: For more than a decade, astronomers have been puzzled by an unexplained surplus of gamma ray signals—the highest energy form of light—that originate at the center of our galaxy, the Milky Way. Known as the Galactic Center Excess (GCE), this diffuse glow has prompted many exciting hypotheses, including the idea that it may be driven by collisions between particles of dark matter, an enigmatic substance that makes up most of the mass in the universe.
Now, scientists led by Anuj Gautam, a Masters student at the Australian National University, have presented new evidence that the GCE is powered by a population of rapidly spinning dead stars, known as millisecond pulsars, that are individually invisible, but could together produce the strange gamma-ray glow, which stretches for about 5,000 light years in every direction around the galactic center.
The team suggests that these extreme stellar corpses could “naturally reproduce the morphology, spectral shape and intensity of the GCE signal” and, “as a bonus,” may also be responsible for a “mysterious microwave ‘haze’ from the inner galaxy,” according to a study published on Thursday in Nature Astronomy... (MORE - details)