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A Supermassive Black Hole Gets Blamed for Quenching Star Formation
Some of the most massive galaxies in the Universe appear to be missing a lot of stars. That seems unusual, since birthing stars is one of a galaxy’s main tasks as it grows. According to Xin “Cindy” Xiang of the University of Michigan, something is suppressing or quenching the births of stars in these galaxies, and she thinks that black holes might be the culprit.
Xiang led a team of researchers who used the X-Ray Imaging and Spectroscopy Mission (XRISM) to study outflows from the accretion disks of black holes. Such regions are bright in X-rays, due to the fantastically high energies expended by material in the disks. Depending on the strength of winds coming from the region, they may play a very important role in affecting star formation. However, the team needed extremely high-resolution spectral studies of the emissions from the black hole to understand what was happening. “Previously, without XRISM, we could only see broad features of the outflows,” Xiang said. “But you need to be able to resolve fine features to answer important questions. What is their structure and geometry? How are the winds launched and when are they launched?”
Creating an Environment that Suppresses Stars
Supermassive black holes, like their smaller counterparts (the stellar-mass black holes), feed on material that gets caught in their strong gravitational pull. That includes light, as well as gas, dust, and anything bigger (such as stars) that tends to stray too close. The material swirls in through an accretion disk that forms around the black hole. The disk, particularly around a supermassive one, is an incredibly energetic environment. The activity there mixes gas and dust particles, and the whole thing is threaded through with magnetic fields. All that motion creates friction, and gravity works as well to atomize the material.
If things are energetic enough, they can even peel electrons off of those atoms, creating a very hot, very bright plasma. Like a bubbling cauldron, this disk can also fling out material, creating powerful winds. If the winds are strong enough, they can blow away gas in nearby regions. Unfortunately, that gas is what galaxies need to form new stars. So, black holes can have a pretty deleterious effect on the starbirth activity nearby.
Catching the Black Hole’s Outflow
Xiang and her team used XRISM to study activity near the supermassive black hole at the heart of galaxy NGC 4151. It supplied a high-resolution look at the winds flowing from the accretion disk at the heart of this active galactic nucleus (AGN) and measured their characteristics. AGN typically occur during a supermassive black hole’s growth phase, and their energetic activities shape the evolution of the host galaxy. They grow by gobbling up gas, as well as influencing surrounding gas clouds. They emit those powerful energetic winds during the growth phase.
This is what’s happening in the core of NGC 4151 as it gorges on nearby material and creates the accretion disk. “With XRISM, we have the greatest resolution observing the brightest AGN, and we’re getting the richest information on outflows that we have observed so far for an accretion disk,” Xiang said.
A Hubble Space Telescope view of the galaxy NGC 4151. Note the bright blue regions of starbirth out in the spiral arms, while there are relatively few regions near the core. Credit: NASA, ESA, Joseph DePasquale (STScI)
What XRISM Tells Us
It turns out that the strongest winds that shape the galaxy and eat up the gas that stars need to form don’t flow all the time. Xiang had to come up with a way to understand when those winds are the strongest. So, she analyzed hundreds of days of NGC 4151 observations, looking for peaks in X-ray brightness that would indicate strong winds.
An illustration of the winds and accretion disk around a supermassive black hole that makes up an AGN. Credit: NASA/M.Weiss (Chandra X-ray Center)
In addition, she looked at how hard or soft the X-rays were detected by XRISM so she could correlate them with wind strength. She put all these variables into a metric that she called the “color intensity index”, or “cindicity”. “Partly because my name is Cindy,” Xiang said. “But the idea is that, in the future, you could tell me the cindicity of your source at this moment and I can tell you the probability that you’re seeing a fast outflow.”
For NGC 4151, Xiang found the fast winds were strongest when the X-rays were hard but faint. The fastest winds were not seen during flares, but typically about 10,000 seconds—or just under 3 hours later—providing the first direct timing link to the outflows.
How Winds Affect Star Formation
As mentioned, the principal effect of an AGN on surrounding gas clouds in a galaxy is pretty catastrophic for starbirth regions. The winds can simply blow the gas away, dispersing it throughout the galaxy or into intergalactic space. If it’s spread out widely enough, there won’t be enough in any given region to begin the process of star formation. The winds can also shred the gas molecules, which also affects star formation.
The black hole’s main activity, gobbling down material, also removes the available star formation material completely. The result is the same: no gases to coalesce into stars. In turn, the galaxy loses its chance to grow through star formation.
Xiang’s team found multiple types of disk winds in the outflows from NGC 4151. All of these outflows had outflow rates that were equal to or greater than the mass accretion rate, meaning they were blowing essential material away. The team’s measurements and conclusions about the winds flowing from this galaxy’s supermassive black hole will help astronomers predict when such outflows are happening in other galaxies. That, in turn, could enhance scientists’ understanding of AGNs across the Universe.
For More Information
Revealing How and When a Black Hole’s Mighty Winds Can Squash Star Formation
XRISM Spectroscopy of Accretion-driven Wind Feedback in NGC 4151
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Surveillance Prices. Hidden Fees. Shifting Costs. This Madness Must Stop.
It’s time to combat commercial surveillance with stronger laws on fair pricing.
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Dry Martian Meteorite Reveals Early Water in Mars’s Crust
Billions of years ago, Mars was hypothesized to have been a habitable world with flowing liquid water and the potential for life. But directly studying its ancient past is currently limited to orbiters and rovers, as scientists have yet to obtain direct samples from Mars. However, meteorites have been found on Earth to have potentially originated from Mars during large impacts that flung chunks of the Red Planet into space, eventually being grabbed by Earth’s gravity and crashing into the Earth’s surface.
Now, an international team of scientists might be one step closer to piecing together Mars’ watery ancient past, and specifically how much water could have flowed across the Red Planet’s surface long ago. In findings recently published in the Geophysical Research Letters, a collaborative team of researchers led by the Technical University of Denmark investigated an intriguing meteorite with an even more intriguing name, “Black Beauty”, with the scientific designation of Northwest Africa 7034 (NWA 7034). What makes Black Beauty so intriguing is its designation as the only known meteorite that originated from the crust of Mars, having been blasted away during an impact billions of years ago, as Black Beauty is estimated to be about 4.4 to 4.5 billion years old.
Using a combination of X-ray and neutron tomography, the researchers analyzed Black Beauty with the goal of ascertaining if the ancient meteorite contained traces of water, also called hydrous materials in the scientific community. While X-ray tomography is used to identify the densest parts of Black Beauty while focusing on iron and silicon, neutron tomography was used to identify that previous “holes” found by normal X-rays were actually hydrous materials.
“Neutrons are particularly sensitive to hydrogen,” said Dr. David Mannes, who is a scientist at the Paul Scherrer Institute (PSI), a co-author on the study. Dr. Mannes collaborated with fellow study co-author, Dr. Anders Kaestner, on the neutron tomography at PSI. “In combination with X-ray tomography, we were not only able to detect tiny hydrated minerals, but also, for the first time, visualize larger, macroscopic hydrogen deposits.”
Essentially, the researchers identified that early Mars contained a water reservoir large enough to engage with the Martian surface and crust, resulting in water deposits into crustal rocks that eventually became Black Beauty. The researchers also note these materials are similar to materials found in Jezero Crater by NASA’s Perseverance rover. Therefore, Black Beauty continues to add a growing pile of evidence that Mars was a much warmer and wetter planet billions of years ago.
While Black Beauty has revealed intricate details regarding ancient Mars and its watery past, arguably the most famous meteorite from Mars is the Allan Hills 84001 (ALH84001) meteorite, which was recovered in Antarctica on December 27, 1984. However, it wasn’t until 1996 before scientists discovered it was potentially from Mars, as ALH84001 had initially been designated as an asteroid chunk, which are frequently discovered on Earth. Once scientists studied ALH84001, they discovered it contained unique structures they hypothesized could indicate signs of ancient Martian life.
While their 1996 study published in Science gained worldwide attention, including an official address from President Bill Clinton, the scientific community was quick to claim these features could have formed from non-biological processes. Regardless of its specific origin, both Black Beauty and ALH84001 demonstrate the importance of bringing back samples from Mars to reduce relying on ancient meteorites.
Unfortunately, the long-anticipated NASA-ESA Mars Sample Return mission was canceled by Congress due to ballooning costs, meaning all the sample tubes that NASA’s Perseverance rover has been depositing on the Martian surface is potentially for nought. For now, scientists have to rely on meteorites to unlock the secrets of ancient Mars, but China’s planned Tianwen-3 might be the first to return Mars samples to Earth sometime next decade.
What new insights into the “Black Beauty” meteorite and ancient Mars will researchers make in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!
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Darth Vader to San Diego City Council: The Emperor liked Flock cameras

In a galaxy not so far, far away — well, in San Diego — the controversial police use of Flock surveillance cameras that photograph and record license plate numbers has at least one prominent supporter.
Darth Vader.
“The Emperor is a fan of Flock,” a person wearing a full-body costume of the “Star Wars” villain told a committee of the San Diego City Council this week, referencing Darth Vader’s evil, power-hungry boss, Emperor Palpatine, ruler of the Galactic Empire.
“And we must continue utilizing Flock technologies so that we can follow and surveil the Rebel scum as they move from playground to playground, from playground to pool, from pool to gymnasium,” the person said during public comments at a Wednesday meeting of the Public Safety and Livable Neighborhoods Committee.
The cosplayer, who breathed heavily into the microphone a la the movie villain, was formally called to the podium by the name Darth Vader.
It was a stance a bit out of sync with silver screen Darth, who famously told an Imperial stooge who got too braggadocious about the Empire’s planet-destroying Death Star: “Don’t be too proud of this technological terror you’ve constructed.”
But in a twist not quite as big as Darth telling Luke Skywalker he was his daddy, the bad guy in black showed up to the government meeting in San Diego to be sarcastic about Flock cameras. He didn’t actually support them at all.
Nor, it turns out, did a lot of people in the audience, who hoisted signs from the American Civil Liberties Union reading: “Get the Flock Out!”
The cosplayer’s sarcastic endorsement comes as Flock Safety — the company whose more than 120,000 artificial intelligence-enabled license plate readers can be found along roadsides in every state but Alaska — comes under increasing scrutiny by lawmakers, civil rights groups and members of the public who have expressed privacy concerns.
Dozens of mostly smaller cities have deactivated their Flock cameras or ended contracts with the company over concerns that it provides data to the Trump administration that can be used to track down immigrants for deportation.
And recent reporting by the Washington Post uncovered at least 50 instances nationwide in which law enforcement officials were accused of misusing their access to the cameras, largely to stalk former romantic partners or citizens.
Last month, the Los Angeles Police Department announced it was pausing its relationship with Flock, but police officials later said they were in the process of negotiating a new deal with the company that would include more data-sharing safeguards.
Both Mayor Karen Bass and her opponent in the November mayoral election, Councilmember Nithya Raman, have said the city should stop working with Flock.
The company, whose automated license readers document plate data as vehicles drive past, says it has partnerships with 5,000 law enforcement agencies nationwide.
Amid public backlash, the company announced this month several platform changes, including a shorter data retention window and audit tools for law enforcement customers intended to flag abnormal search behavior.
In San Diego, Flock cameras are affixed to streetlights in about 500 locations, according to the 2025 Annual Surveillance Report by the San Diego Police Department.
In addition to plate numbers, the report states, the cameras record the date, time and location of the scan, as well as vehicle descriptors such as make, model and color.
The information is encrypted and transmitted to a secure database that can be accessed only by San Diego police personnel, according to the department. The data is saved for 30 days and automatically deleted unless it is being used as evidence in an active investigation, according to the department.
The report says San Diego police officers last year conducted more than 244,000 investigative searches of the data and that it played a “key role in advancing 361 cases.”
The data, per the department, helped officers recover 259 stolen vehicles and find four missing people, as well as aiding the investigations of around nine of the city’s 28 homicides in 2025.
In a presentation to the Public Safety and Livable Neighborhoods Committee in November, San Diego Police Capt. Charles Lara said the technology “has been truly game-changing for our department, especially while we continue to operate with hundreds of officers below ideal staffing levels.”
Lt. Kristopher McAndrew said the “vast majority of data is never viewed” and that the police department does not share data with federal or out-of-state law enforcement agencies or private entities.
At the meeting this week, Darth Vader — who, like everyone else who approached the podium, was allotted two minutes of speaking time — said of the Flock camera system: “I need this so I can stalk my ex-girlfriend.”
He asked the City Council members how residents will continue to trust them when they continue to vote “for surveillance technology that imprisons them.”
He advised one of the council members to work on her Jedi mind tricks to fool them, then raised his hand to the audience, saying: “Do it like this.”
“This technology will help us find the Rebel scum and their hidden base on Hoth,” he said, referencing the ice planet in the “Star Wars” universe. “This technology will help us find Luke Skywalker as he traverses the universe in his X-wing. This technology is a necessary, necessary force.”
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