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Blog post with audio player, show notes, and transcript: https://www.preposterousuniverse.com/podcast/2023/05/15/236-…al-theory/

Is there a multiverse, and if so, how should we think of ourselves within it? In many modern cosmological models, the universe includes more than one realm, with possibly different laws of physics, and these realms may or may not include intelligent observers. There is a longstanding puzzle about how, in such a scenario, we should calculate what we, as presumably intelligent observers ourselves, should expect to see. Today’s guest, Thomas Hertog, is a physicist and longstanding collaborator of Stephen Hawking. They worked together (often with James Hartle) to address these questions, and the work is still ongoing.

Continue reading “Mindscape 236 | Thomas Hertog on Quantum Cosmology and Hawking’s Final Theory” »

A trio of astrophysicists, two from Colgate University and the third from the University of Texas, has found evidence of dark stars courtesy of data from the James Webb Space Telescope. In their study, reported in Proceedings of the National Academy of Sciences, Cosmin Ilie, Jillian Paulin and Katherine Freese, analyzed three galaxies spotted by the JWST and how they might relate to dark stars.

Back in 2007, Freese, along with Douglas Spolyar and Paolo Gondolo, proposed the idea of a dark star —rather than nuclear fusion, these theorized dark stars are powered by dark matter. Since that time, researchers have continued to study the idea of such a star, built models to show what they might look like and derived a list of characteristics that such a star might have. In the current study, Ilie, Paulin and Freese have found three candidates in Webb data that fit the bill.

Dark stars, the team suggests, likely could have been born during the early days of the universe—like other stars, they would have been made mostly of helium and hydrogen. But they would also contain dark matter—enough to provide a heat source. Such stars would not then be lit by nuclear fusion. If such stars did exist, they would be much larger than other types of stars that have been observed—so large that they might look like galaxies from Earth-based telescopes.

Our universe could be twice as old as current estimates, according to a new study that challenges the dominant cosmological model and sheds new light on the so-called “impossible early galaxy problem.”

“Our newly-devised model stretches the galaxy formation time by a several billion years, making the universe 26.7 billion years old, and not 13.7 as previously estimated,” says author Rajendra Gupta, adjunct professor of physics in the Faculty of Science at the University of Ottawa.

For years, astronomers and physicists have calculated the age of our universe by measuring the time elapsed since the Big Bang and by studying the oldest stars based on the redshift of light coming from distant galaxies. In 2021, thanks to new techniques and advances in technology, the age of our universe was thus estimated at 13.797 billion years using the Lambda-CDM concordance model.

The discovery of low-level ripples throughout the universe called the gravitational wave background has set physicists looking for exotic explanations.

By Alex Wilkins

When you imagine a galaxy like our Milky Way, you’re probably picturing a swirl shape with arms reaching out from a central point. These spiral arms are a classic feature of many galaxies. Similar structures can be found around young stars which are surrounded by disks of matter from which planets form, called protoplanetary disks. Now, astronomers have discovered evidence that these structures could be created by recently formed exoplanets.

Astronomers used Large Binocular Telescope in Arizona to investigate a giant exoplanet named MWC 758c which seems to be forming the spiral arms around its host star. Located 500 light-years away, the star is just a few million years old, making it a baby in cosmic terms. “Our study puts forward a solid piece of evidence that these spiral arms are caused by giant planets,” said lead researcher Kevin Wagner of the University of Arizona in a statement. “And with the new James Webb Space Telescope, we will be able to further test and support this idea by searching for more planets like MWC 758c.”

The star still has its protoplanetary disk of dust and gas around it, making it comparable to the early stages of our own solar system. “I think of this system as an analogy for how our own solar system would have appeared less than 1% into its lifetime,” Wagner said. “Jupiter, being a giant planet, also likely interacted with and gravitationally sculpted our own disk billions of years ago, which eventually led to the formation of Earth.”

NASA’s James Webb Space Telescope has broken a new record by detecting what is now considered the most distant active supermassive black hole to date.

Dr. Varsha Ramachandran from the Center for Astronomy of Heidelberg University (ZAH) and her colleagues uncovered the first “stripped” star of intermediate-mass. This discovery marks a missing link in our picture of stellar evolution toward systems with merging neutron stars, which are crucial to our understanding of the origin of heavy elements, such as silver and gold. Dr. Ramachandran is a postdoc in the research group of Dr. Andreas Sander, located at ZAH’s Astronomisches Rechen-Institut (ARI). These results were now published in Astronomy & Astrophysics.

The team of researchers discovered the first representative of the long-predicted, but as yet unconfirmed population of intermediate-mass stripped stars. “Stripped stars” are stars that have lost most of their outer layers, revealing their hot and dense helium-rich core, which results from the nuclear fusion of hydrogen to helium. Most of these stripped stars are formed in binary star systems in which one star’s strong gravitational pull peels off and accretes matter from its companion.

For a long time, astrophysicists have known of low-mass stripped stars, known as subdwarfs, as well as their massive cousins, known as Wolf-Rayet stars. But until now, they have never been able to find any of the so-called “intermediate-mass stripped stars,” raising questions whether our basic theoretical picture needs a major revision.

Scientists pointed the James Webb Space Telescope at a distant galaxy called CEERS 1019. They found it might be a merger of three galaxies and contains an extremely ravenous black hole.

Woven across our universe is a weblike structure of galaxies called the cosmic web. Galaxies are strung along filaments in this vast web, which also contains enormous voids. Now, astronomers using Webb have discovered an early strand of this structure, a long, narrow filament of 10 galaxies that existed just 830 million years after the big bang. The 3 million light-year.

A light year is the distance that a particle of light (photon) will travel in a year—about 10 trillion kilometers (6 trillion miles). It is a useful unit for measuring distances between stars.