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Category: cosmology – Page 67

In the vast expanse of the cosmos, there is much more than meets the eye. For every kilogram of visible matter in the universe, from the computer on your desk to the distant stars and galaxies, there are 5 kilograms of invisible “dark matter” that permeate our surroundings.

This enigmatic dark matter evades direct observation yet exerts its invisible pull on the visible objects around us.

Fifty years ago, renowned physicist Stephen Hawking proposed a fascinating idea about the nature of dark matter. He suggested that it might consist of a population of black holes that formed in the early stages of the universe, mere moments after the Big Bang.

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Primordial black holes (PBHs)—hypothetical objects formed by the gravitational collapse of dense regions in the early Universe—have been invoked as dark-matter candidates. But for PBHs to constitute all dark matter, they’d have to be extremely light, possibly weighing less than small asteroids. Now Elba Alonso-Monsalve and David Kaiser of the Massachusetts Institute of Technology show that these diminutive PBHs could possess an exotic property—a net color charge (such a charge characterizes quarks and gluons in quantum chromodynamics theory) [1]. Such color-charged PBHs might have left potentially observable signatures, says Kaiser.

Observations rule out that stellar-mass PBHs could fully explain dark matter, but PBHs weighing between 1017 and 1022 g remain viable candidates. Since a PBH’s mass should relate to its age, this mass range corresponds to PBH formation immediately after the big bang, when the Universe was still a hot plasma of unconfined quarks and gluons. Most PBHs would have formed by engulfing large numbers of quarks and gluons having a distribution of color charges. These PBHs would be color-charge neutral and sufficiently massive to live until today. However, the duo’s calculations show that a few PBHs could have formed from regions so tiny that the charges of the absorbed gluons would be correlated, giving these PBHs a net charge.

Color-charged black holes have long been considered to be mathematically possible, but the new study is the first to propose a realistic formation mechanism, says Kaiser. The small sizes imply that they would have since evaporated. Yet their presence in the early Universe might have disrupted the distribution of protons and neutrons when the big bang created the first nuclear isotopes, leaving subtle traces in the cosmic abundance of the elements.

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New findings reveal magnetic fields in three massive stars in the Magellanic Clouds, shedding light on the influence of magnetism on stellar evolution and the formation of neutron stars and black holes. The use of advanced spectropolarimetry techniques was crucial to overcome past observational challenges.

Magnetic fields have been discovered in three massive, hot stars within our neighboring galaxies, the Large and Small Magellanic Clouds, for the first time. Although magnetic fields in massive stars are not new to our own galaxy, their detection in the Magellanic Clouds is particularly significant due to the abundance of young, massive stars in these galaxies. This discovery offers a rare chance to investigate actively forming stars and explore the maximum mass a star can achieve while maintaining stability.

Impact of magnetism on star evolution.

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Researchers for the first time showed, how gravity can exist without mass, providing an alternative theory that could potentially mitigate the need for dark matter…

Dark matter is a hypothetical form of matter that is implied by gravitational effects that can’t be explained by general relativity unless more matter is present in the universe than can be seen. It remains virtually as mysterious as it was nearly a century ago when first suggested by Dutch astronomer Jan Oort in 1932 to explain the so-called “missing mass” necessary for things like galaxies to clump together.

Now Dr. Richard Lieu at The University of Alabama in Huntsville (UAH) has published a paper in the Monthly Notices of the Royal Astronomical Society that shows, for the first time, how gravity can exist without mass, providing an alternative theory that could potentially mitigate the need for dark matter.

“My own inspiration came from my pursuit for another solution to the gravitational field equations of general relativity—the simplified version of which, applicable to the conditions of galaxies and clusters of galaxies, is known as the Poisson equation—which gives a finite gravitation force in the absence of any detectable mass,” says Lieu, a distinguished professor of physics and astronomy at UAH, a part of the University of Alabama System.

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The American theoretical physicist, Brian Greene explains various hypotheses about the causation of the big bang. Brian Greene is an excellent science communicator and he makes complex cosmological concepts more easy to understand.

The Big Bang explains the evolution of the universe from a starting density and temperature that is currently well beyond humanity’s capability to replicate. Thus the most extreme conditions and earliest times of the universe are speculative and any explanation for what caused the big bang should be taken with a grain of salt. Nevertheless that shouldn’t stop us to ask questions like what was there before the big bang.

Brian Greene mentions the possibility that time itself may have originated with the birth of the cosmos about 13.8 billion years ago.

To understand how the Universe came to be, scientists combine mathematical models with observations and develop workable theories which explain the evolution of the cosmos. The Big Bang theory, which is built upon the equations of classical general relativity, indicates a singularity at the origin of cosmic time.

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Discover the groundbreaking Self-Interacting Dark Matter (SIDM) theory that suggests dark matter particles might collide and interact with each other. Learn how recent studies on the El Gordo galaxy cluster support this revolutionary idea, potentially changing our understanding of the universe’s structure and evolution. Dive into the cosmic dance and stay updated with the latest space discoveries!

Chapters:
00:00 Introduction.
00:44 The Dance of Self-Interacting Dark Matter.
02:39 Unveiling the Strengths and Weaknesses of CDM and SIDM
05:14 Exploring Dark Matter: Methods and Future Prospects.
09:20 Outro.
09:37 Enjoy.

Best Telescopes for beginners:
Celestron 70mm Travel Scope.
https://amzn.to/3jBi3yY

Celestron 114LCM Computerized Newtonian Telescope.

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As opposed to black holes, white holes are thought to eject matter and light while never absorbing any. Detecting these as yet hypothetical objects could not only provide evidence of quantum gravity but also explain the origin of dark matter.

No one today questions the existence of black holes, objects from which nothing, not even light, can escape. But after they were first predicted in 1915 by Einstein’s general theory of relativity, it took many decades and multiple observations to show that they actually existed. And when it comes to white holes, history may well repeat itself. Such objects, which are also predicted by general relativity, can only eject matter and light, and as such are the exact opposite of black holes, which can only absorb them. So, just as it is impossible to escape from a black hole, it is equally impossible to enter a white one, occasionally and perhaps more aptly dubbed a “white fountain”. For many, these exotic bodies are mere mathematical curiosities.

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