A cosmologist explains the mind-bending hypothesis that our universe could have branched off from a black hole singularity in another universe.
Category: cosmology – Page 144
The orbits of 27 stars orbiting closely around the black hole at the center of our Milky Way are so chaotic that researchers cannot predict with confidence where they will be in about 462 years. This finding emerges from simulations by three astronomers based in the Netherlands and the United Kingdom. The researchers have published their findings in two papers in the International Journal of Modern Physics D and in the Monthly Notices of the Royal Astronomical Society.
Simulating 27 stars and their interactions with each other and with the black hole is easier said than done. For centuries, for example, it was impossible to predict the motions of more than two interacting stars, planets, rocks, or other objects. It was only in 2018 that Leiden researchers developed a computer program in which rounding errors no longer play a role in the calculations. With this, they were able to calculate the motions of three imaginary stars. Now the researchers have expanded their program to deal with 27 stars that, by astronomical standards, move close to the black hole at the center of the Milky Way.
The simulations of the 27 massive stars and the black hole resulted in a surprise. Although the stars remain in their orbits around the black hole, the interactions between the stars show that the orbits are chaotic. This means that small perturbations caused by the underlying interactions change the orbits of the stars. These changes grow exponentially and, in the long run, make the star orbits unpredictable.
Jayanne English (U. Manitoba), Nathan Deg (Queen’s University) & WALLABY Survey, CSIRO/ASKAP, NAOJ/Subaru Telescope.
Polar ring galaxies are an intriguing class with a distinct and perplexing structure. These galaxies are distinguished by a ring of stars, gas, and dust significantly tilted to the galaxy’s main disk.
Atomic clocks are the most accurate timekeeping instruments we have. A new study proposes a way to use the instruments’ mind-blowing level of precision to detect the tiniest of energy fluctuations, potentially giving scientists a way to observe some types of dark matter.
Dark matter continues to prove elusive: though we haven’t observed it directly, we can see its effects on the Universe. Frustratingly, there is nothing in our current models of physics to explain what we see.
Here, researchers from the University of Sussex and the National Physical Laboratory in the UK have suggested using atomic clocks to detect certain low-mass particles theorized to potentially make up this mysterious material.
A spherical structure nearly one billion light-years wide has been spotted in the nearby Universe, dating all the way back to the Big Bang.
For a few hours after a star smashes into a supermassive black hole, some of the brightest light in the Universe is produced.
The subsequent flash of radio waves were thought to simmer down within weeks or months of a collision. It turns out we might have been a little impatient to turn our gaze elsewhere.
An international team of astrophysicists has witnessed radio waves bursting from material surrounding an assortment of supermassive black holes hundreds of days after they ripped apart a star, suggesting many collisions could be responsible for a serious case of cosmic indigestion.
As the universe evolves, scientists expect large cosmic structures to grow at a certain rate: dense regions such as galaxy clusters would grow denser, while the void of space would grow emptier.
But University of Michigan researchers have discovered that the rate at which these large structures grow is slower than predicted by Einstein’s Theory of General Relativity.
They also showed that as dark energy accelerates the universe’s global expansion, the suppression of the cosmic structure growth that the researchers see in their data is even more prominent than what the theory predicts. Their results are published in Physical Review Letters.
The case for a small universe
Posted in cosmology
The universe is big, as Douglas Adams would say.
The most distant light we can see is the cosmic microwave background (CMB), which has taken more than 13 billion years to reach us. This marks the edge of the observable universe, and while you might think that means the universe is 26 billion light-years across, thanks to cosmic expansion it is now closer to 46 billion light-years across. By any measure, this is pretty darn big. But most cosmologists think the universe is much larger than our observable corner of it. That what we can see is a small part of an unimaginably vast, if not infinite creation. However, a new paper published on the arXiv preprint server argues that the observable universe is mostly all there is.
In other words, on a cosmic scale, the universe is quite small.
Roman Space Telescope team is integrating a complex electrical harness, crucial for the spacecraft’s communication and power. After a detailed two-year construction and a preparatory “bakeout” process, assembly into the spacecraft is ongoing, with future installations planned for power components.
NASA’s Nancy Grace Roman Space Telescope team has begun integrating and testing the spacecraft’s electrical cabling, or harness, which enables different parts of the observatory to communicate with one another. Additionally, the harness provides power and helps the central computer monitor the observatory’s function via an array of sensors. This brings the mission a step closer to surveying billions of cosmic objects and untangling mysteries like dark energy following its launch by May 2027.
On Sept. 6, a new satellite left Earth; its mission is to tell us about the motions of hot plasma flows in the universe.
Launched from Tanegashima Space Center in Japan, the X-Ray Imaging and Spectroscopy Mission (XRISM) satellite will detect X-ray wavelengths with unprecedented precision to peer into the hearts of galaxy clusters, reveal the workings of black holes and supernovae, as well as to tell us about the elemental makeup of the universe.
XRISM, pronounced “crism,” is a collaborative mission between the Japan Aerospace Exploration Agency (JAXA) and NASA, with participation by the European Space Agency.