A new paper theorizes that in rare cases, gravitational waves could propagate across the universe like a laser.
Category: cosmology – Page 113
Ever since the James Webb Space Telescope (JWST) captured its first glimpse of the early universe, astronomers have been surprised by the presence of what appear to be more “ultramassive” galaxies than expected. Based on the most widely accepted cosmological model, they should not have been able to evolve until much later in the history of the universe, spurring claims that the model needs to be changed.
This would upend decades of established science.
“The development of objects in the universe is hierarchical. You start small and get bigger and bigger,” said Julian Muñoz, an assistant professor of astronomy at The University of Texas at Austin and co-author of a recent paper published in Physical Review Letters that tests changes to the cosmological model. The study concludes that revising the standard cosmological model is not necessary. However, astronomers may have to revisit what they understand about how the first galaxies formed and evolved.
Last year, the Keck Cosmic Web Imager, also atop Maunakea, caught the first direct light emanating from wispy web filaments that cross one another and stretch across the darkest corners of space. These are filaments that sit isolated between galaxies, in the largest and most hidden portions of the cosmic web.
“Seeing” the location of dark matter around these cosmic web strands is a completely different story, however.
That’s because, despite making up an estimated 85% of all the matter in the universe, dark matter is invisible because it doesn’t interact with light like everyday matter that comprises stars and dust does.
ESA’s Euclid mission was launched in July 2023 and has already sent home test images showing that its instruments are ready to go. Now, the space telescope begins mapping huge swaths of the sky, focusing on an area for 70 minutes at a time. Throughout its 6-year mission, it will complete 40,000 of these ‘pointings’, eventually observing 1.5 billion galaxies in the sky. Astronomers will use this map to measure how dark matter and dark energy have changed over time.
The interior of black holes remains a conundrum for science. In 1916, German physicist Karl Schwarzschild outlined a solution to Albert Einstein’s equations of general relativity, in which the center of a black hole consists of a so-called singularity, a point at which space and time no longer exist. Here, the theory goes, all physical laws, including Einstein’s general theory of relativity, no longer apply; the principle of causality is suspended.
This constitutes a great nuisance for science—after all, it means that no information can escape from a black hole beyond the so-called event horizon. This could be a reason why Schwarzschild’s solution did not attract much attention outside the theoretical realm—that is, until the first candidate for a black hole was discovered in 1971, followed by the discovery of the black hole in the center of our Milky Way in the 2000s, and finally the first image of a black hole, captured by the Event Horizon Telescope Collaboration in 2019.
In 2001, Pawel Mazur and Emil Mottola proposed a different solution to Einstein’s field equations that led to objects that they called gravitational condensate stars, or gravastars. Contrary to black holes, gravastars have several advantages from a theoretical astrophysics perspective.
Our understanding of how galaxies form and the nature of dark matter could be completely upended after new observations of a stellar population bigger than the Milky Way from more than 11 billion years ago that should not exist.
A paper published today in Nature details findings using new data from the James Webb Space Telescope (JWST). The results find that a massive galaxy in the early universe —observed 11.5 billion years ago (a cosmic redshift of 3.2)—has an extremely old population of stars formed much earlier—1.5 billion years earlier in time (a redshift of around 11). The observation upends current modeling, as not enough dark matter has built up in sufficient concentrations to seed their formation.
Swinburne University of Technology’s Distinguished Professor Karl Glazebrook led the study and the international team, who used the JWST for spectroscopic observations of this massive quiescent galaxy.
The picture was the result of the first six months of operation of eROSITA (Extended Roentgen Survey with an Imaging Telescope Array), one of two X-ray telescopes that were launched into space in July 2019 aboard the Russian spacecraft SRG (Spectrum-Roentgen-Gamma). eROSITA scans the sky as the spacecraft spins, and collects data over wider angles than are possible for most other X-ray observatories. This enables it to slowly sweep the entire sky every six months.
By an unusual arrangement, the eROSITA team is split into two — with a group based in Germany and one based in Russia — and each has exclusive access to eROSITA data from only half of the sky. The mission was originally intended to cover the sky eight times. But Russia’s full-scale invasion of Ukraine in 2022 led the German government to freeze its collaborations, and eROSITA was put on stand-by. By then, it had completed four full sky scans.
The data that Bulbul and her collaborators have used so far were from their half of the sky, collected during the first scan. Even so, the results are already among the most precise cosmological measurements ever made. It is unclear when the Russia-based group will publish its data and analysis.
EROSITA telescope shows galaxies’ “clumpiness” matches predicted effect of dark energy, dark matter.
Stranger Stars
Posted in cosmology, particle physics
Some of the most bizarre and interesting objects in the Universe are stars. Let’s go on a journey and discover what happens when physics is taken to the most extreme.
Chapters:
00:00 Intro.
03:33 Red dwarfs.
04:53 White dwarfs.
06:39 Black Dwarfs.
08:15 Neutron stars.
13:36 Quark stars.
15:58 Strange stars.
16:35 Electroweak stars.
17:38 Planck stars.
Sources:
All about star birth, life, and death:
https://en.wikipedia.org/wiki/Stellar…
About neutron stars:
https://www.space.com/22180-neutron-s…
What happens inside a black hole? Nobody knows!
https://www.space.com/what-happens-bl…
What is a Planck star? — Ask a Spaceman! Dr. Paul M. Sutter.