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Observationally, these two structures were viewed as products of separate formation processes, with observational surveys showing no clear correlation between their masses and sizes. However, the formation process is not understood, and realistic simulations have so far been lacking.

This long-standing mystery is now challenged by a new galaxy simulation from the SMUGGLE-Ring project, offering a fresh perspective and bridging theory and observations. In a paper accepted as a Letter to the Editor in Astronomy & Astrophysics, AIP researcher Dr. SungWon Kwak and collaborators demonstrate, for the first time, that a fully self-consistent, high-resolution hydrodynamical simulation of a Milky Way–like barred galaxy can naturally form both a nuclear star cluster and a nuclear stellar disk and follow their growth over billions of years. The paper is available on the arXiv preprint server.

The bar feeds both structures

The simulation reveals that the galaxy's stellar bar plays a central role in this process. "Our simulation achieves this by showing how the galactic bar acts like a cosmic conveyor belt, channeling gas inward to feed both structures simultaneously from the same reservoir," Kwak explains. As gas accumulates in the central region, stellar feedback from dying stars generates shocks that repeatedly trigger new episodes of star formation. Over the course of several billion years, hundreds of millions of solar masses of stars are assembled in these central structures.

One of the key advantages of the simulation is that it allows researchers to observe processes that cannot be directly seen in real galaxies. Astronomical observations provide only a single snapshot of a galaxy at the present day. By contrast, the simulation follows the evolution of the galaxy over four billion years, allowing scientists to watch the stellar bar form, trace the inward flow of gas, monitor bursts of star formation and observe how the nuclear stellar disk grows outward from the center over time.

Why the link looks hidden

The results also explain why observations have struggled to reveal a clear connection between nuclear star clusters and nuclear stellar disks. "The apparent disconnection does not mean that the stars themselves differ fundamentally in age, chemical composition, or motion," explains Dr. Cristina Chiappini, also an AIP scientist and co-author of the study.

Instead, the simulation shows that the structural relationship between the two components naturally evolves over time. During long periods of steady growth, the relative masses and sizes of the cluster and the disk gradually drift apart. As a result, the nuclear star clusters and nuclear stellar disks of galaxies observed at different stages of their evolution can appear remarkably different, even if the underlying growth mechanism is the same.

Live dark matter changes the picture

Including realistic dark matter dynamics in the simulation plays a crucial role in this finding. "Previous studies rely on fixed background potentials for the galactic bar and dark matter halo, but the realistic dynamical treatment of stars and the dark matter halo using live particles in our model allows us to form a realistic bar that evolves over time and then naturally forms nuclear structures," explains Dr. Ivan Minchev, co-author of the study.

"Furthermore, our model also exhibits a 'dark gap' around the bar region, which is found in many observations and is known as evidence of the interaction between stars and dark matter driven by the rotation of the stellar bar."

A merger may reshape the core

The picture becomes even more fascinating because, in the simulation, a particularly massive star cluster with roughly 30 million solar masses spirals into the galactic center and merges with the nuclear star cluster. Interestingly, recent observations have captured such massive star clusters inside the bar of NGC 1365, some of which are expected to spiral into its center and merge with the galaxy's nuclear star cluster. Such merger events can alter the mass and size of the nuclear star cluster over a short time scale.

This makes the coevolution history of galactic centers more complex, yet interesting, since a supermassive black hole is lurking inside the nuclear star cluster in galaxies. Consequently, these merger events might leave an imprint on the mass of the supermassive black hole, potentially expanding the connection between galactic components and allowing us to interpret future observations.

Publication details

SungWon Kwak et al, SMUGGLE-Ring: Evolutionary link between nuclear star cluster and nuclear disk, arXiv (2026). DOI: 10.48550/arxiv.2606.05157

Who's behind this story?

Lisa Lock

BA art history, MA material culture. Former museum editor, paramedic, and transplant coordinator. Editing for Science X since 2021. Full profile →

Robert Egan

Bachelor's in mathematical biology, Master's in creative writing. Well-traveled with unique perspectives on science and language. Full profile →

Citation: Milky Way-like simulation reveals how central galactic structures grow together (2026, August 6) retrieved 6 August 2026 from https://phys.org/news/2026-08-milky-simulation-reveals-central-galactic.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. %!s()

Even before it was released, it was clear that the quirky life sim Tomodachi Life: Living the Dream was going to be a Switch hit. What nobody could have guessed was just how popular the slice-of-life game would be. The newest Tomodachi Life game didn't just do well on Nintendo's older platform: it outdid a number of major franchises on Switch 2.

According to Nintendo's most recent financial report, Tomodachi Life has sold a total of 7.96 million units for Nintendo Switch. For the sake of comparison, other 2026 releases for Nintendo Switch 2, like Star Fox and Yoshi and the Mysterious Book have each sold fewer than 1 million copies. The veritable sensation Pokémon Pokopia has sold at least 3.6 million copies as of early June, but that figure does not include Japanese sales, which are reported by The Pokémon Company. That incomplete number still placed Pokopia in the top five best-selling Switch 2 games, though.

Based on current numbers, Living the Dream has evidently outsold multiple brand stalwarts combined, on what is technically on an older platform. Of course, some of those people must have played the newest Tomodachi game on the newer console, which is backwards comptabile. The latest sales figures haven't been updated on Nintendo's site, but the new report suggests that Tomodachi Life is outperforming many releases on Switch 2, despite releasing on an older platform.

Players who tried the 2026 game Nintendo exclusive may not be surprised by its success. The game, which allows custom Mii characters to interact with one another in absurd ways, is rife with moments made for social media virality. The title is also surprisingly permissive for a Nintendo game. Players can fill their Tomodachi island with content that would normally be filtered or banned on most platforms. Rather than creating a cesspool of content, the lack of censorship has only helped Tomodachi Life stand out amid a stacked lineup of classic video game franchises.

Correction: This article has been edited to reflect Tomodachi Life: Living the Dream is a Nintendo Switch release, not a Nintendo Switch 2 exclusive. %!s()

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• list 1 of 3Fauci invokes Fifth Amendment in heated COVID-19 Senate hearing
• list 2 of 3US Senate’s Fauci hearing renews COVID origin debate but reveals little
• list 3 of 3Why did Anthony Fauci invoke the Fifth Amendment? US hearing explained

Fauci, the former Director of the National Institute of Allergy and Infectious Diseases (NIAID), charged that the Republican-led hearing was designed to entrap him. He had previously been pre-emptively pardoned by former President Joe Biden after a politically divisive government response to the pandemic, which included school closures and vaccine promotion.

In his opening statements last week, Fauci accused the committee chairman, Republican Senator Rand Paul of Kentucky, of having an “unhinged obsession” with him, arguing he had previously cooperated in several congressional hearings and investigations following the pandemic.

“The only conclusion I can reach is that the sole reason he is calling me before this committee is to get me to say something – anything – that could vindicate his repeated public pledges that I end up, in his words – quote – ‘behind bars’,” Fauci said.

After the vote on Thursday, the panel could refer Fauci to the Department of Justice for possible criminal prosecution.

Speaking before the vote, Democratic Senator Richard Blumenthal of Connecticut said there was “virtually no chance that a court would actually approve any contempt because [Fauci] had a well-founded fear of self-incrimination, which entitled him to invoke the Fifth Amendment”.

Rand, meanwhile, argued that Fauci’s decision to deliver an opening statement decrying the hearing before invoking his Fifth Amendment right during questioning, showed he was “trying to have it both ways”.

Democrats and critics have charged that last week’s hearing, which comes six years after the pandemic spread across the US, was a purely political exercise that shed no new light on the issue.

Several Republicans have for years accused Fauci of leading an intentional effort to mislead the public on the origins of the COVID-19 pandemic, charging he downplayed the possibility the virus may have emerged from a lab in Wuhan, China, and not from a nearby wet market via natural animal-to-human transmission. Fauci has denied he ever outright dismissed the “lab leak” theory.

The origin of the virus remains unknown, but surveys have found a majority of experts in the field believe available evidence indicates natural transmission over a lab leak.

Nevertheless, Republican President Donald Trump’s White House has fully embraced the lab leak theory, launching a website last year highlighting several claims that experts said gloss over the nuance of the debate.

Trump’s health and human services secretary, Robert F Kennedy Jr, a vaccine sceptic, has also been a top critic of Fauci. Before last week’s hearing, Republicans on the Senate committee released several of Fauci’s diary entries, which had been provided by the secretary.

The diaries contained no smoking gun proving Fauci intentionally misled the public although they did include some uncomfortable revelations.

Those included Fauci recounting advising then-New York City Mayor Bill de Blasio and an aide to California Governor Gavin Newsom on COVID-19 restrictions, including the closing of schools and businesses. Condemnation of such closures became a politically potent cause for Republicans in the wake of the pandemic.

The vote on Thursday comes just before midterm elections in November.

What happens next?

It was not immediately clear what the next steps would be.

Typically, the issue would be brought to a full Senate vote before referral to the DOJ. That would require passing a 60-vote threshold, only attainable if several Democrats break from their party. Paul has said he wants to bypass the process and directly refer the matter to the DOJ with an accompanying legal brief.

Under federal law, it is illegal for a person called as a witness before the Senate or the US House of Representatives to “refuses to answer any question pertinent to the question under inquiry”.

Still, Fauci’s lawyers have maintained that he remains on solid legal ground in invoking his constitutional right to remain silent to avoid self incrimination.

Senator Gary Peters, the top Democrat on the Senate panel, said the vote on Thursday contradicted the longstanding practice of lawmakers respecting the right of witnesses to invoke their fifth amendment rights.

“If this committee now seeks to punish a witness for asserting their constitutionally protected Fifth Amendment rights, future witnesses will argue that appearing before Congress exposes them to punishment regardless of whether they comply with a subpoena and invoke a constitutional protection,” he said.

Biden’s pre-emptive pardon of Fauci covers only his actions from January 1, 2014 through January 19, 2025. The former president has said he granted the pardon due to a fear of political prosecutions, and not because he believed Fauci had committed any wrongdoing.

If convicted of a contempt of Congress charge, Fauci could face a maximum sentence of a year in prison and a fine of $100,000. %!s()

Toyota's hybrid subcompact SUV meets the needs of most drivers. It has room for groceries, fits up to five passengers, and gets gas mileage that can save you a few bucks at the pump compared with other options. It doesn't excel in any of these categories, but few vehicles ever do. And with an attractive starting price of $31,390 for the hybrid ($26,930 for the nonhybrid), the Corolla Cross is a respectable option for people who don't want to think much about their car.

Toyota refreshed the Corolla Cross for 2026, and the difference is mostly visible in its grille. While the nonhybrid version keeps a chunkier, rugged look, the hybrid takes on sleeker front styling that mimics Toyota's other hybrid offerings. Black trim around the fenders gives both models a hint of visual pizazz along the sides, and simple body lines provide an overall pleasant design language. The Agreeable Gray vehicle fittingly comes in a couple of shades of gray, along with a few other colors, including Cavalry Blue, which made our Hybrid XSE test car easier to spot in a parking lot.

The 2026 refresh was cosmetic only, so the Corolla Cross Hybrid continues to use a 2.0-liter inline-four engine and electric motors at both axles that net a combined 196 horsepower, along with a continuously variable automatic transmission. While the vehicle is front-wheel-drive biased, all-wheel drive will electronically engage when the Cross senses the need for extra grip, such as during a launch, in corners, and on slippery surfaces. When that happens, the rear motor kicks into action.

Just as before, the Corolla Cross Hybrid is more of a Sunday driver than a speed demon, but this powertrain has two important advantages over the 169-hp base version. Our test model reached 60 mph in 7.6 seconds, which is 1.6 seconds quicker than an all-wheel-drive nonhybrid model that we previously tested. The Corolla Cross Hybrid returned 39 mpg in our 75-mph highway fuel-economy test, a 9-mpg boost over the nonhybrid XLE we tested.

The Corolla Cross is easy to live with and use. The controls you probably reach for most, such as climate and volume, are still governed by buttons and knobs. The steering wheel's simple layout makes it easy to set cruise control, switch between songs, and change information settings on the digital gauge cluster without doing much searching.

The infotainment is refreshingly simple too. Toyota's in-house system is clean and effective, though we'd venture that most drivers will prefer to connect their phone via wireless Apple CarPlay or Android Auto. The $38,469 XSE we tested had the 12.3-inch digital gauge cluster and an optional JBL stereo system that offers a pretty good thump.

Ride quality is pleasant, and while there's some bumpiness when the Corolla Cross goes over potholes and railroad tracks, it's still relatively smooth and recovers easily. The softer ride gives it a bit of body roll on curves, but not to the point that the Corolla Cross feels like a mess. Steering is overassisted, but the small SUV generally behaves exactly as you'd expect it to, which is pretty much all that shoppers in this segment want.

Pair the unsurprising ride with Toyota's swath of driver-assistance features, and you've got a vehicle that's great for drivers who are new, have anxiety, or simply want an extra set of eyes on the road. The Corolla Cross comes standard with adaptive cruise control, lane-departure warning with steering assist, lane tracing, and automatic high-beams. The XSE also has blind-spot monitoring and rear-cross-traffic alert.

Our biggest gripe with the Cross is its engine, which is about as enthusiastic as you might be at 3 o'clock on a Monday. The four-pot does its job but seems like it would rather be taking a nap. The electric motors help give the hybrid a nudge off the jump, but practically any tap of the throttle will engage the engine, which emits a steady groan thanks to a transmission that doesn't simulate shifting. The engine drone is fairly loud, especially when the vehicle is reaching highway speeds. We recorded 81 decibels at wide-open throttle.

HIGHS: Simple controls, easy to drive, decent fuel efficiency.

As for the interior design, Toyota designers reheated the Corolla sedan's pizza. It mostly works, but the Corolla Cross is missing some storage space that would've made it feel more functional as an SUV. The bulky gearshift housing and cupholder setup leave little room for the center armrest, and aside from a bit of storage inside the center console, the only other places to stash things are the glovebox and a small pocket behind the passenger's seat. The bulky motif continues throughout, even appearing in the form of inexplicably thick sun visors.

LOWS: Unenthusiastic powertrain, lacks storage space, clunky interior.

The seats are generally comfortable, but we think they could use more padding. So could the armrests on the center console and doors. The XSE's seats wear snazzy blue stripes that help make an otherwise unexciting cabin feel a bit more fun. But overall, trim materials feel bottom-spec, even in the highest-trim XSE model. The cabin is full of hard plastic and plain styling.

The Cross competes with the Kia Niro Hybrid and the Subaru Crosstrek Hybrid, which offer similar features in similar-size packages. The Niro costs less and boasts a higher-end interior but lags behind a bit in acceleration. The Crosstrek has slightly lower fuel economy than the Corolla Cross but offers marginally better off-roading capability.

VERDICT: It might be the auto industry's Agreeable Gray, but the Corolla Cross Hybrid delivers on its promise of being a practical car at a practical price.

The Corolla Cross is far from exciting, but with simple, modern styling and an attractive price, it's a solid choice for those who aren’t fixated on their car's specs.

➡️ Skip the lot. Let Car and Driver help you find your next car.

Specifications

Specifications

2026 Toyota Corolla Cross Hybrid XSE AWD
Vehicle Type: front-engine, front- and rear-motor, all-wheel-drive, 5-passenger, 4-door wagon

PRICE
Base/As Tested: $35,425/$38,469
Options: Convenience package (tilt-and-slide sunroof, power liftgate), $1250; JBL Premium Audio, $800; crossbars, $330; Connected Services trial offering, $325; doorsill protectors, $179; mudguards, $160

POWERTRAIN
DOHC 16-valve 2.0-liter Atkinson-cycle inline-4, 150 hp, 139 lb-ft + 3 permanent-magnet synchronous AC motors (combined output: 196 hp; lithium-ion battery pack)
Transmissions, F/R: continuously variable automatic/direct-drive

CHASSIS
Suspension, F/R: struts/multilink
Brakes, F/R: 12.0-in vented disc/11.1-in disc
Tires: Goodyear Assurance Finesse
225/55R-18 98H M+S

DIMENSIONS
Wheelbase: 103.9 in
Length: 176.8 in
Width: 71.9 in
Height: 64.8 in
Passenger Volume, F/R: 52/35 ft3
Cargo Volume, Behind F/R: 44/22 ft3
Curb Weight: 3405 lb

C/D TEST RESULTS
60 mph: 7.6 sec
1/4-Mile: 15.8 sec @ 88 mph
100 mph: 21.1 sec
110 mph: 26.8 sec
Results above omit 1-ft rollout of 0.3 sec.
Rolling Start, 5–60 mph: 8.1 sec
Top Gear, 30–50 mph: 4.0 sec
Top Gear, 50–70 mph: 5.6 sec
Top Speed (gov ltd): 114 mph
Braking, 70–0 mph: 178 ft
Roadholding, 300-ft Skidpad: 0.79 g

Interior Sound
Idle: 33 dBA/2 sone
Full Throttle: 81 dBA
70-mph Cruising: 74 dBA/33 sone

C/D FUEL ECONOMY
Observed: 35 mpg

EPA FUEL ECONOMY
Combined/City/Highway: 42/46/39 mpg

Alayna Wilkening grew up reading motorsport magazines and following her grandpa around his Chevrolet dealership's showroom floor. In true Hoosier fashion, her first car was a hot pink custom cardboard "Fiero-vette" for her kindergarten Kindy 500 race. She now autocrosses a 1994 Miata with her dad, which she learned to drive the night before her first event. Alayna went to Indiana University and graduated with a degree in journalism and a minor in graphic design. As a testament to her great taste in cars, her first real one was a metallic orange 2007 Chevy HHR, which she lovingly called "The Dumptruck."   %!s()

It comes as official attendance data, published on Thursday, suggested school absence rates in England remained above pre-pandemic levels, with nearly one in five pupils missing at least 10% of school in the 2025/26 academic year.

Education minister Paul Waugh said the new attendance targets would take each school's local challenges into account, but that "every school has a role to play to improve attendance".

Before the Covid pandemic, when many schools closed to pupils for significant periods of time, attendance rates at English mainstream state schools regularly stayed above 95%, but schools have struggled to get back to those rates in the years since.

Thursday's figures, external suggested an overall attendance rate of 93% for 2025/26, a slight decrease on the previous year. That includes both authorised absences, such as illness, and unauthorised absences, which is when pupils miss school without permission or a valid reason.

The rates of persistent absence have doubled since the pandemic. A pupil is described as persistently absent if they miss at least 10% of school sessions.

In 2018/19, persistent absence rates for England state schools were around 10%, while the most recent data showed it was at 19% in 2025/26.

Pupils on free school meals and those with special educational needs and disabilities (SEND) were also still more likely to be absent from school than their peers.

Many mainstream schools in England were given attendance targets specific to their school in a widespread trial last year, but on Thursday the Department for Education (DfE) confirmed that every school would be getting their own target and that it would be monitored for the first time.

The BBC understands there will be no immediate penalties for schools who miss their attendance targets, but that the DfE will get in touch with schools that are off-track to make sure they are aware and taking action.

Schools could then be pointed towards best practice guidance, or encouraged to join with other schools in a local behaviour and attendance hub.

The regulator Ofsted already considers a schools' overall attendance rates in their inspections.

In an opinion piece published in The Independent newspaper on Thursday, newly-appointed education minister Paul Waugh said the latest attendance stats showed "progress has slowed over the past year", and that the government's response needed to be "broader, smarter and more ambitious".

Schools have been promised access to more data tools in the coming year to help them analyse individual pupils' attendance records, Waugh said, so they can identify concerns earlier and be "intervening more quickly when pupils begin to drift away from regular attendance".

Fridays are "becoming a particular weak spot for attendance", he added, and said he would be investigating why pupil illness absences are regularly significantly higher at the end of each week.

He called on schools to put on interesting clubs and enrichment sessions on Fridays "so every child stays engaged right through to the end of the week".

Paul Whiteman, general secretary of schools leaders' union NAHT, said Thursday's attendance data showed "just how hard it is to drive absence rates back down to pre-pandemic levels".

"Schools already go above and beyond in encouraging attendance, but it isn't a problem that they can solve alone or that government targets will fix," he said.

"The issue often has roots beyond the classroom, from illness and mental health challenges to poverty and unmet special educational needs."

He said it highlighted the importance of the government's upcoming reforms to the SEND system in England.

The data released on Thursday also showed that nearly 12% of pupils missed school in the week beginning Monday 22 June, when an exceptional heatwave was affecting parts of England, leading to the highest absence rate of the year. %!s()