Tag Archives: Simulations

Revolutionary Cosmological Simulations Illuminate Black Hole Growth in the Early Universe

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Revolutionary simulations from Maynooth University astronomers reveal that, at the onset of the dense and turbulent universe, “light seed” black holes could swiftly consume matter, rivaling the supermassive black holes found at the centers of early galaxies.

Computer visualization of a baby black hole growing in an early universe galaxy. Image credit: Maynooth University.

Dr. Daksar Mehta, a candidate at Maynooth University, stated: “Our findings indicate that the chaotic environment of the early universe spawned smaller black holes that underwent a feeding frenzy, consuming surrounding matter and eventually evolving into the supermassive black holes observed today.”

“Through advanced computer simulations, we illustrate that the first-generation black holes, created mere hundreds of millions of years after the Big Bang, expanded at astonishing rates, reaching sizes up to tens of thousands of times that of the Sun.”

Dr. Louis Prowl, a postdoctoral researcher at Maynooth University, added: “This groundbreaking revelation addresses one of astronomy’s most perplexing mysteries.”

“It explains how black holes formed in the early universe could quickly attain supermassive sizes, as confirmed by observations from NASA/ESA/CSA’s James Webb Space Telescope.”

The dense, gas-rich environments of early galaxies facilitated brief episodes of “super-Eddington accretion,” a phenomenon where black holes consume matter at a rate faster than the norm.

Despite this rapid consumption, the black holes continue to devour material effectively.

The results uncover a pivotal “missing link” between the first stars and the immense black holes that emerged later on.

Mehta elaborated: “These smaller black holes were previously considered too insignificant to develop into the gigantic black holes at the centers of early galaxies.”

“What we have demonstrated is that, although these nascent black holes are small, they can grow surprisingly quickly under the right atmospheric conditions.”

There are two classifications of black holes: “heavy seed” and “light seed.”

Light seed black holes start with a mass of only a few hundred solar masses and must grow significantly to transform into supermassive entities, millions of times the mass of the Sun.

Conversely, heavy seed black holes begin life with masses reaching up to 100,000 times that of the Sun.

Previously, many astronomers believed that only heavy seed types could account for the existence of supermassive black holes seen at the hearts of large galaxies.

Dr. John Regan, an astronomer at Maynooth University, remarked: “The situation is now more uncertain.”

“Heavy seeds may be rare and depend on unique conditions for formation.”

“Our simulations indicate that ‘garden-type’ stellar-mass black holes have the potential to grow at extreme rates during the early universe.”

This research not only reshapes our understanding of black hole origins but also underscores the significance of high-resolution simulations in uncovering the universe’s fundamental secrets.

“The early universe was far more chaotic and turbulent than previously anticipated, and the population of supermassive black holes is also more extensive than we thought,” Dr. Regan commented.

The findings hold relevance for the ESA/NASA Laser Interferometer Space Antenna (LISA) mission, set to launch in 2035.

Dr. Regan added, “Future gravitational wave observations from this mission may detect mergers of these small, rapidly growing baby black holes.”

For further insights, refer to this paper, published in this week’s edition of Nature Astronomy.

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D.H. Meter et al. Growth of light seed black holes in the early universe. Nat Astron published online on January 21, 2026. doi: 10.1038/s41550-025-02767-5

Source: www.sci.news

Astronomers conduct simulations of undetected asteroids within our galaxy

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Astronomers discover large planets around other stars more often than small planets.whether to measure The gravitational pull of an exoplanet on its host starobserve How much starlight do exoplanets block?or Take a photo of the exoplanet itselfObservation methods for exoplanets are biased toward planets with masses twice the mass of Earth, or 12 septillion kilograms or more. But astronomers know that small planets exist. It's just harder to find because the smaller the planet, the more accurate equipment is needed.

Astronomers call planets smaller than Earth: sub-earth or asteroid. Current telescopes are bad at finding these tiny planets, so astronomers rely on simulations to determine how they behave. A team of astronomers studied the conditions of a hypothetical planetary system containing only asteroids. They argued that understanding where asteroids are likely to appear in large numbers will allow scientists to better understand how common these types of planets are.

To obtain a representative sample of the right conditions for planetary systems to form, astronomers simulation codeGenerate models of exoplanets similar to actual observations. Using this code, the team ran 33 sets of 1,000 simulations, each set with different starting parameters. Most stars in the Milky Way are in that size range, so they simulated a system containing stars ranging from 1/2 to 5 times the mass of the Sun. They ran all but the last two sets of simulations over a billion years of simulation time.

The first set was their point of comparison. This demonstrated that the code would produce a system containing asteroids given the same conditions as a solar system in which planets smaller than Earth are known to exist. In the next set of eight, they varied the mass of the host star, the spread of mass within the disk of matter's starting point, and the ratio of gas to dust in the system. The astronomers then ran four sets of experiments varying the period during which the asteroid could accumulate new material, ranging from 320,000 to 32 million years. The researchers ran 16 more sets, varying the amount of dust the system needed to start with, from exactly the same mass of Earth to 10,000 times the mass of Earth.

The astronomers' last four sets of simulations varied depending on the host star's mass, which ranges from 1.5 to 5 times the mass of the Sun. They ran their two largest sets on shorter timescales than the rest because large stars burn out their fuel faster and have shorter lifetimes than smaller stars. At the end of a star's life, it expands, sometimes quite dramatically. Scientists used these sets to find scenarios in which the star swallows the asteroid as it expands, and scenarios in which the star survives.

The researchers noted that computing power limits the scope of the simulation, as certain systems cannot perform calculations on more than 1,000 objects at once. Also, ice and rock were not allowed to accumulate at the edges of the system, as they do in real star systems. They said these factors limit the accuracy of models of planet formation processes and long-term system dynamics, respectively.

Overall, the research team found that asteroids should be extremely abundant in the universe. They found that under the parameters they studied, systems consisting of only planets between 1 and 110 million times the mass of Earth could “easily form.” They suggested that estimates of how often planets form around stars may significantly underestimate the actual frequency of planets.

Astronomers have found that the most important factor determining how large an asteroid becomes is the amount of dust it can initially form. But they also found that systems containing only small planets stop forming when the initial available dust exceeds 100 times the mass of Earth. Their final conclusions dealt with the outermost asteroids of certain systems, which are more than 10 times the distance from Earth to the Sun. They found that although these planets rarely grow larger than small moons, they can survive the star's inevitable expansion and persist for billions of years after the star's expansion.


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Source: sciworthy.com

The Possible Collapse of AMOC: Simulations Highlight Real Danger of Stopping Atlantic Currents

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Ocean currents flowing from the tropics to the North Atlantic have a major influence on Europe's climate.

jens carsten roseman

As the planet warms, is there a serious risk that the Atlantic Current that warms Europe will slow down and stop? Yes, according to the most detailed computer simulation ever performed. The likelihood of this scenario remains highly uncertain.

“We have demonstrated that it is indeed possible with our current setup,” he says. René van Westen At Utrecht University in the Netherlands.

Now, warm water, made more salty by evaporation, flows north from the tropics along the surface of the Atlantic Ocean, keeping Europe much warmer than it would otherwise be. When this water cools, it sinks because it becomes more salty and denser. It then returns to the tropics and flows along the ocean floor into the southern hemisphere.

This is known as the Atlantic Meridional Overturning Circulation (AMOC). Studies of past climate suggest that the dramatic cooling episodes that have occurred around Europe over the past 100,000 years or so have been associated with so-called tipping points, when reverse currents slow down or stop completely, and small changes in may convert one system to another. state.

The cause is thought to be melting ice sheets. The influx of large amounts of fresh water into the North Atlantic reduces salinity, which in turn reduces surface water density and reduces the amount of water that sinks.

However, this has proven difficult to model. Most shutdown simulations require adding unrealistically large amounts of fresh water at once. Some also question whether this is a potential tipping point, since recent simulations using more advanced models have not shown any shutdowns.

Now, van Westen's team has run the most sophisticated simulation to date, which took a total of six months to run on the Dutch state-run supercomputer Sunellius. It was very expensive, he says.

Unlike previous simulations, the team added fresh water gradually rather than all at once. This created a positive feedback that amplified the effect. The decrease in salinity reduced the amount of water sinking, which reduced the amount of brine flowing north, further reducing salinity.

This eventually broke the overturning circulation, causing temperatures to rise in the Southern Hemisphere but plummet in Europe. For example, in this model, London would be 10°C (18°F) cooler on average, and Bergen, Norway would be 15°C (27°F) cooler on average. Other impacts include localized sea level rise in areas such as the East Coast of the United States.

Additionally, some of the changes seen in the model before the collapse are consistent with changes seen in the real Atlantic Ocean in recent decades.

But to cause this collapse, the researchers had to run the model for 2,500 years. And they needed to add huge amounts of fresh water. Although less than previous simulations, it is still about 80 times the amount that is currently flowing into the ocean from the melting Greenland ice sheet. “So it's absurd and not very realistic,” Van Westen said.

Furthermore, this simulation did not include global warming. The team now plans to rerun the simulation with that in mind.

“This is the most cutting-edge model in which such experiments have been performed,” he says. Peter Ditlefsen He is a co-author of a 2023 study predicting that the Atlantic overturning current could break up between 2025 and 2095, based on changes in sea surface temperatures.

The model suggests it will take large amounts of fresh water and centuries to stop the circulation from reversing, but why do we think climate models are underestimating the risk of nonlinear changes like the Atlantic tipping point? There are several, Ditlefsen said.

Climate models need to divide the world into large cubes to make their calculations workable, he says, and this has a smoothing effect. Additionally, the model has been calibrated based on how well it simulates the 20th century climate, although there was a linear relationship between greenhouse gas emissions and the resulting changes. may not be applicable in the future.

“We should expect the model to be less sensitive than the real world,” Ditlevsen says.

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Source: www.newscientist.com