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Category: cosmology – Page 128

A New, More Accurate Measurement for the Clumpiness of the Universe

Cosmologists are wrestling with an interesting question: how much clumpiness does the Universe have? There are competing but not compatible measurements of cosmic clumpiness and that introduces a “tension” between the differing measurements. It involves the amount and distribution of matter in the Universe. However, dark energy and neutrinos are also in the mix. Now, results from a recent large X-ray survey of galaxy clusters may help “ease the tension”

The eROSITA X-ray instrument orbiting beyond Earth performed an extensive sky survey of galaxy clusters to measure matter distribution (clumpiness) in the Universe. Scientists at the Max Planck Institute for Extraterrestrial Physics recently shared their analysis of its cosmologically important data.

“eROSITA has now brought cluster evolution measurement as a tool for precision cosmology to the next level,” said Dr. Esra Bulbul (MPE), the lead scientist for eROSITA’s clusters and cosmology team. “The cosmological parameters that we measure from galaxy clusters are consistent with state-of-the-art cosmic microwave background, showing that the same cosmological model holds from soon after the Big Bang to today.”

Microscopic Origin of the Entropy of Black Holes in General Relativity

In the 1970s, physicists Bekenstein and Hawking used general relativity and quantum mechanics in curved spacetime to propose that black holes behave as thermodynamic objects. They found that black holes carry an entropy described by a remarkable formula that applies for any mass, charge, angular momentum, or spacetime dimension. Here, we use new results at the interface of quantum information theory and quantum gravity to address an outstanding challenge: how to explain the microscopic origin of this formula.

In quantum mechanics, entropy measures the logarithm of the dimension of the space of microstates consistent with the macroscopic description of a system. We show that, in any theory of gravity that reduces to general relativity with matter at low energies, there are infinite families of states that have geometries identical to the black hole outside the horizon but different structures inside. We show that these states overlap quantum mechanically because of gravitational wormholes. The overlaps have a dramatic consequence: The microstates span a space whose dimension equals the exponential of the Bekenstein-Hawking entropy formula.

This explanation of black-hole entropy does not require new forms of matter and involves a novel description of all black-hole microstates as quantum superpositions of objects having geometric semiclassical descriptions. Our results also imply a macroscopic manifestation of quantum mechanics in cosmic settings: We show that one can understand long Einstein-Rosen bridges between universes as quantum superpositions of short bridges.

Sagittarius A*: Spinning Black Hole Shapes Spacetime into Football

“A spinning black hole is like a rocket on the launch pad,” said Dr. Biny Sebastian. “Once material gets close enough, it’s like someone has fueled the rocket and hit the ‘launch’ button.”

The center of our Milky Way Galaxy is exhibiting spinning behavior while warping the spacetime environment, according to a recent study published in the Monthly Notices of the Royal Astronomical Society. A team of international researchers led by Penn State University investigated the spinning patterns of the supermassive black hole at the center of the Milky Way, Sagittarius A* (Sgr A•, which is located approximately 26,000 light-years from Earth, and holds the potential to help astrophysicists better understand the behavior of black holes throughout the cosmos.

“A spinning black hole is like a rocket on the launch pad,” said Dr. Biny Sebastian, who is a researcher in the Department of Physics & Astronomy at the University of Manitoba and a co-author on the study. “Once material gets close enough, it’s like someone has fueled the rocket and hit the ‘launch’ button.”

For the study, the researchers analyzed data sets from six archival observations obtained by the Chandra X-Ray Observatory, which has been using its powerful instruments to study the cosmos since its launch in July 1999. Using a method that was developed in a 2019 study by the current study’s lead author, Dr. Ruth Daly, the researchers determined that Sagittarius A* was spinning in such a manner that it is warping the surrounding spacetime environment into a football shape, which becomes flatter as the spin increases and is driven by the surrounding matter and the black hole’s magnetic field. The researchers concluded that if the amount of this matter and magnetic field’s strength change in the future, this could alter the amount of energy the spin exerts out into space.

Bubble-Like ‘Stars Within Stars’ Could Explain Black Hole Weirdness

Once hypothetical monsters born in a tangled nest of Einstein’s general theory of relativity, black holes are now recognized as bona fide celestial objects as real as stars, moons, and galaxies.

But make no mistake. Their engines are still as mysterious as they were when the German theoretical physicist Karl Schwarzschild first played with Einstein’s field equations and came to the conclusion that space and time could pucker up into pits of no return.

Goethe University Frankfurt physicists Daniel Jampolski and Luciano Rezzolla have gone back to step one in an attempt to make better sense of the equations that describe black holes and have come away with a solution that’s easier to picture, if no less bizarre.

“Beyond What’s Possible” — Webb Space Telescope Discovers Mysterious Ancient Galaxies

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 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 that used the JWST for spectroscopic observations of this massive quiescent galaxy.