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Category: cosmology – Page 23

An international team of astronomers have investigated a large Galactic supernova remnant designated G278.94+1.35. Results of the study, published Dec. 30 on the pre-print server arXiv, shed more light on the properties of this remnant.

Supernova remnants (SNRs) are diffuse, expanding structures resulting from a supernova explosion. They contain ejected material expanding from the explosion and other interstellar material that has been swept up by the passage of the shockwave from the exploded star.

G278.94+1.35 is a supernova remnant in the Milky Way, discovered in 1988. It has an estimated linear diameter of about 320 light years and its age is assumed to be about 1 million years. The distance to G278.94+1.35 is estimated to be some 8,800 light years.

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Astronomers using the James Webb Space Telescope have used a distortion in space to reveal over 40 individual stars in a galaxy 6.5 billion light-years from the Milky Way—halfway back to the beginning of the universe. It’s the largest number of individual stars ever detected in the distant universe.

The unique image, which takes advantage of JWST’s high-resolution optics, was only possible because the light from 44 stars in a distant galaxy was magnified by a massive cluster of galaxies in front of it called Abell 370.

This technique, called gravitational lensing—also known as an “Einstein ring” because it was predicted by the famous scientist Albert Einstein—works when the gravitational field of a foreground object distorts the space around it. Light is bent from an object behind it into circular rings or arcs, both revealing the existence of something in the background and, crucially, magnifying it by factors of hundreds or even thousands. In this case, an arc was visible, dubbed the “Dragon Arc.”

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Scientists are diving deep into the origins of supermassive black holes, using recent gravitational wave detections as a key tool.

By leveraging signals from smaller black holes, researchers hope to detect the harder-to-catch waves from supermassive pairs, potentially unlocking the secrets of their formation and growth.

Unveiling the mystery of supermassive black holes.

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For the first time, the NASA/ESA/CSA James Webb Space Telescope has detected and “weighed” a galaxy that not only existed about 600 million years after the Big Bang, but also has a mass that is similar to what our Milky Way galaxy’s mass might have been at the same stage of development.

Other galaxies Webb has detected at this period in the history of the universe are significantly more massive. Nicknamed the Firefly Sparkle, this galaxy is gleaming with star clusters—10 in all—each of which researchers examined in great detail. Their work is published in Nature.

“I didn’t think it would be possible to resolve a galaxy that existed so early in the universe into so many distinct components, let alone find that its mass is similar to our own galaxy’s when it was in the process of forming,” said Lamiya Mowla, co-lead author of the paper and an assistant professor at Wellesley College in Massachusetts. “There is so much going on inside this tiny galaxy, including so many different phases of star formation.”

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There might not be a mysterious ‘dark’ force accelerating the expansion of the Universe after all. The truth could be much stranger – bubbles of space where time passes at drastically different rates.

The passage of time isn’t as constant as our experience with it suggests. Areas of higher gravity experience a slower pace of time compared with areas where gravity is weaker, a fact that could have some pretty major implications on how we compare rates of cosmic expansion according to a recently developed model called timescape cosmology.

Discrepancies in how fast time passes in different regions of the Universe could add up to billions of years, giving some places more time to expand than others. When we look at distant objects through these time-warping bubbles, it could create the illusion that the expansion of the Universe is accelerating.

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Back when the Universe was new, following the Big Bang some 13.8 billion years ago, galaxies took a bit of time to assemble themselves from the surrounding primordial soup.

A new discovery right at the end of the Cosmic Dawn is challenging how long we thought that assembly took. JWST has spotted a huge, ultramassive galaxy as it appeared 12.8 billion years ago, so intricately structured that it can only belong to the most spectacular category of galaxies: the grand design spiral.

The galaxy’s name is Zhúlóng, after the Torch Dragon of Chinese myth, and its discovery has been detailed in a paper uploaded to preprint server arXiv ahead of peer review and publication.

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ABSTRACT. We reanalyse the Pantheon+ supernova catalogue to compare a cosmology with non-FLRW evolution, the timescape cosmology, with the standard Lambda cold dark matter (⁠|Lambda$|CDM) cosmology. To this end, we analyse the Pantheon+ for a geometric comparison between the two models. We construct a covariance matrix to be as independent of cosmology as possible, including independence from the FLRW geometry and peculiar velocity with respect to FLRW average evolution. This framework goes far beyond most other definitions of model independence. We introduce new statistics to refine Type Ia supernova (SNe Ia) light-curve analysis. In addition to conventional galaxy correlation functions used to define the scale of statistical homogeneity we introduce empirical statistics that enables refined analysis of the distribution biases of SNe Ia light-curve parameters |beta c$| and |alpha x_1$|⁠. For lower redshifts, the Bayesian analysis highlights important features attributable to the increased number of low-redshift supernovae, the artefacts of model-dependent light-curve fitting, and the cosmic structure through which we observe supernovae. This indicates the need for cosmology-independent data reduction to conduct a stronger investigation of the emergence of statistical homogeneity and to compare alternative cosmologies in light of recent challenges to the standard model. Dark energy is generally invoked as a place-holder for new physics. For the first time, we find evidence that the timescape cosmology may provide a better overall fit than |Lambda$|CDM and that its phenomenology may help disentangle other astrophysical puzzles. Our from-first-principles reanalysis of Pantheon|$+$| supports future deeper studies between the interplay of matter and non-linear spacetime geometry in a data-driven setting.

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Year 2021 face_with_colon_three

The quasi-local notion of an isolated horizon is employed to study the entropy of black holes without any particular symmetry in loop quantum gravity. The idea of characterizing the shape of a horizon by a sequence of local areas is successfully applied in the scheme to calculate the entropy by the S O(1, 1) BF boundary theory matching loop quantum gravity in the bulk. The generating function for calculating the microscopical degrees of freedom of a given isolated horizon is obtained. Numerical computations of small black holes indicate a new entropy formula containing the quantum correction related to the partition of the horizon. Further evidence shows that, for a given horizon area, the entropy decreases as a black hole deviates from the spherically symmetric one, and the entropy formula is also well suitable for big black holes.

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