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JWST Spies Once-hidden Treasures in the W51 Starbirth Crèche
Star formation is a dramatic and complex process that erupts throughout the Universe. Yet, a lot of that action gets hidden by clouds of gas and dust. That’s where observatories such as the James Webb Telescope JWST and the Atacama Large Millimeter Array (ALMA) come in handy. They use infrared light and radio waves respectively, to pierce the veil surrounding the process of starbirth.
A team led by University of Florida doctoral candidate Taehwa Yoo recently used to JWST to make observations of the giant Milky Way starbirth region Westerhout 51 (W51). It lies about 17,000 light-years away from Earth in the direction of the constellation Sagittarius. The images and data they collected revealed many fine details of the star-formation activity going on there. “With optical and ground-based infrared telescopes, we can’t see through the dust to see the young stars,” said Adam Ginsburg, Ph.D., a professor of astronomy at UF. “Now we can.”
An overview of W51A region. The composite image is produced by combining NIRCam F360M (blue), F410M (green), and MIRI F560W (red) on JWST. The north and east directions in ICRS coordinates are marked as arrows at the upper left corner. Courtesy Yoo, et al.
Despite the impressive images and data, some aspects of star birth remain hidden away behind clouds too dense even for JWST to pierce. The team compared their JWST images to observations of the same region made by the ALMA, and found that only a fraction of stars are detectable by both telescopes. The observations that JWST did make, however, showed a lot of detail in the structures it could see. And that provides astronomers with new insights into the starbirth process. “Because of James Webb, we can see those hidden, young massive stars forming in this star-forming region,” Yoo said. “By looking at them, we can study their formation mechanisms.”
Digging Into W51’s Starbirth Activity
Cutout images of specific regions in W51. (a) A dust filament around W51-E. (b) W51-IRS2 protocluster. (c) Cometary objects around W51-IRS2 (these are globules of dust that look like comets, sculpted by radiation from nearby stars). (d) W51-E protocluster. (e) A bar at the edge of IRS1 H II region. (An HII region is a cloud of mostly hydrogen gas from which stars can form.) (f) W51 IRS1 H II region shell structure. (g) W51b1 H II region. (h) W51b2 H II region and YSOs. (i) W51e7 H II region. (j) W51c1 H II region. (k) and (l) Newly discovered H II regions. Courtesy Yoo, et al.
W51 is divided into several regions of enhanced star formation. As part of the observations, JWST zeroed in on the W51A region, the youngest starbirth crèche in the area. Multiple clouds of ionized gas and warm dust exist there, with some of the dust arranged in filaments. The science team also spotted a good example of a cavity around one of the newborn stars, which indicates that the star is “eating away” at its birthplace. They also studied giant gas bubbles of gas, dark dust filaments (which are likely still-hidden crèches), cometary objects, and protostellar jets streaming away from protostellar objects. Each of these are part of the starbirth process.
The team focused on the massive protoclusters called W51-E and W51-IRS2, using the Near Infrared Camera (NIRCAM) and the Mid-infrared Instrument (MIRI). Most of the stars they were able to observe are still accreting material and hadn’t yet reached their full masses. Some have only formed in the past million years or so.
Yoo’s group estimates there are about 10,000 solar masses of stars in W51A. Many are very young, massive stars, and not a lot is known about their earliest infancy, which is what fascinates astronomers today. In some areas, those remain hidden by too-thick clouds of gas and dust. Luckily, W51A has a lot to offer based on previous studies made by the Atacama Large Millimeter/submillimeter Array (ALMA). That radio array in Chile detected over 200 compact sources referred to as “PPOs (Pre/Protostellar Objects)” in the region. These are places where stars are actively forming or will start to form in the relatively near future. Astronomers want to know what kickstarts the process of star formation in regions like these, and what stages occur as massive young stars begin to form.
Combined observations from JWST and ALMA show the location of protocluster regions where multiple stars are forming. The locations of the matching sources are marked in the upper panel with the background image of F162M, F210M, and F480M filters on JWST. In the lower panels, W51-E and W51-IRS2 protocluster regions are zoomed in with the background image of the JWST NIRCam filters and ALMA 1.3 mm image combined. Courtesy Yoo, et al.
Starbirth Stages
In a general sense, astronomers know the overall process of starbirth: clouds of gas and dust condense and form hot cores called “young stellar objects.” These are where the future star will be born. After a period of accretion, the star reaches a point where it begins fusing hydrogen to helium in its core. That’s the point where the star is born. Before that, the star begins as that hot core, and also blows material away from itself via a superheated jet. High-mass stars born like this obviously affect their environment, especially in their birth crèches. They interact with neighboring clouds of gas, which affects the formation of sibling stars in the same region. The radiation from those high-mass stars can even go so far as to rip apart the clouds of gas. That chokes off the available material for new stars to form. From the JWST images and data, it’s clear that each of those steps is in process in the W51A cloud.
In a recent paper in the Astrophysical Journal (noted below), Yoo and the team point out that several hot cores with rich chemistry associated with massive protostars exist in W51A. These are very likely sites of maser emissions from several varieties of molecules in the gas clouds crèches, including OH (hydroxide), CH3OH (methanol), SiO (silicon monoxide), NH3 (ammonia), and CS (carbon monosulfide). The presence of these masers acts as a tracer for dense molecular clouds where stars are expected to form (if they aren’t doing so already).
In addition to the hot cores that indicate the very early stellar birth process, the team also observed at least one “knot” of emission from a protostellar object. It indicates ionized iron and hydrogen within the cloud. They think it’s from a jet streaming from a hot young star that’s heating up and affecting the nearby interstellar medium.
This latest look at W51 with JWST gives astronomers a much better idea of what different stages of starbirth look like, stages that are normally hidden from optical observations. The quality of the JWST data revealed more information and showed new structures in the area that astronomers can now use to more fully explain the process of starbirth. “They are not the first photos of this region, but they are the best,” said Ginsburg. “They’re so much better that they essentially are brand new photos. Every time we look at these images, we learn something new and unexpected.”
For More Information
Researchers Use JWST to Reveal Hidden Details of W51 Star Formation
A JWST NIRCam/MIRI view of the W51A high-mass star-forming region
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ICE shootings protested in Pasadena on National Day of Action
Approximately 50 demonstrators gathered Saturday morning in Pasadena as part of a national action to honor lives lost during immigration enforcement operations and in detention centers during the Trump administration.
They wore fliers around their necks, hung with yellow thread, bearing the smiling faces and names of some of the 75 people who have died since January 2025.
“Killed by ICE” was printed above a photo of each person, including local resident Roberto Carlos Montoya Valdez, a 52-year-old killed while trying to flee immigration agents who descended on a Home Depot in Monrovia last year.
The Los Angeles residents, part of the San Gabriel Foothills Indivisible group, carried American flags and held signs that read “No ICE No War” and “Stop ICE Murders.”
“Good morning, Pasadena,” Betsy Hanger, an organizer with the group, boomed into a megaphone as she walked through an intersection. “Honk for democracy. Honk if you want ICE off our streets now.”
A chorus of horns sounded as drivers signaled their support.
Organizer Andra Clarke held a banner in each hand that read “Neighbors Say ICE Out.” The sign around her neck carried the name and photo of Francisco Gaspar-Andrés, a 48-year-old who died in a Texas detention center in December.
Heba Turner was among protesters demanding justice for those killed by ICE officers.
(Myung J. Chun / Los Angeles Times)
Clarke, 61, said the group has been gathering at the intersection of Colorado Boulevard and Fair Oaks Avenue every Saturday since March. Last weekend, they celebrated civil rights activist John Lewis.
This Saturday, though, their focus was aimed at ICE.
“Now 75 people have died at the hands of ICE,” Clarke said. “We were originally told, ‘Oh they’re going to go after the criminals, the people who are the worst of the worst.’ That’s a lie; that is not what’s happening.
“They’re targeting communities, they’re targeting people of color. It’s fascism. … Anybody who cares about humanity should care about what’s happening.”
Clarke said it hit her hard when she learned of the two recent deaths at the hands of ICE.
The event was also a vigil honoring 52-year-old Lorenzo Salgado Araujo, who was killed by an ICE agent in Houston on July 7 while driving his construction crew to a job site, and Johan Sebastian Guerrero, 25, who was fatally shot by an ICE officer in Maine during a traffic stop earlier this month.
“It’s like, again? It just doesn’t end. It feels like it never ends — the evil.”
Shortly before noon, Clarke used a megaphone to read aloud the names of the dozens who have died. After each name read, Hanger struck a singing bowl, the vibrations sounding out in the corner where they stood. At times, she read “unidentified man” or “four unidentified women.”
Next to them was a poster board with a photo of Daphy Michel, a 31-year-old woman found unresponsive at a bus shelter in Pittsburgh after ICE released her “into cold winter conditions and no care for mental health episodes or notice to relatives.”
“Let’s take a moment of silence for all those who were taken,” Clarke said, bowing her head.
“It’s like, again? It just doesn’t end. It feels like it never ends — the evil,” said Andra Clarke, an organizer for San Gabriel Foothills Indivisible.
(Myung J. Chun / Los Angeles Times)
Among those gathered to listen was Leticia Lopez, a 65-year-old South Pasadena resident whose voice trembled as she talked about the impact of hearing about another arrest or death tied to enforcement operations.
“It gets me to the core,” she said, striking her chest. “It’s not getting any better, it’s getting worse. I just feel like I need to do something.”
Lopez, who wore a shirt that read “Immigrants are not criminals but the president is,” said her mother and grandmother were forcefully repatriated from Arizona to Mexico.
Her mother, who was raised in Mexico, later met her father there. He moved to the U.S. in the 1950s as a bracero. Hearing the stories of today, she said, “triggers everything that they went through.”
“When I see it happening, it’s a generational trauma that I feel,” she said. Lopez said people around her are carrying passports and documents in public to prove they’re citizens.
“Because they’re afraid they might be profiled, picked up, kidnapped by ICE. When my son goes out, I worry,” she said of her 28-year-old.
Later that afternoon, about four miles away outside of Home Depot in Pasadena, organizers staked in the ground dozens of white crosses that bore photos of the dead — the majority of them men. Attendees of the vigil laid flowers at the crosses in a makeshift cemetery.
“Shot dead by ICE,” read one with a photo of Keith Porter Jr., who was killed by an off duty ICE officer in California.
Several of them contained details of how the deaths unfolded. A man killed after a tractor trailer struck him as he fled an ICE raid in Florida. A Cuban immigrant who died in a detention center (his death was later ruled a homicide). A Mexican national who fell 30 feet to his death during a raid in California.
Among the photos on crosses were Renee Good and Alex Pretti.
“Are we going to wait until 70 more die to do something?” asked Marlom Portillo, an educator with the National Day Laborer Organizing Network, as he staked more crosses into the ground.
“What they want us to do is forget them,” Portillo added. “We will never get tired of denouncing this atrocity.”
“There are more people who died than there are people here protesting,” Kathleen Vallee, a Monrovia resident, observed to her friend. “And that says a lot about us.”
Vallee said when she attended the “No Kings” protest, it was “jam-packed.” Only a dozen people had gathered around 20 minutes into the vigil.
“It turns my stomach,” Vallee said, hands clasped. “This just seems to be seeping up from the sewer into our democracy and that motivates me.”
As the small crowd assembled, demonstrators carried signs that read “Every person is sacred,” “we keep us safe” and “neighbors say ICE out.” One woman carried a handmade sign that read: “Who will they come for next?”
Sheri Lochner, a 64-year-old Monrovia resident, is part of East Pasadena Community Defense Corner, a small group that “provides support and a sense of community” for day laborers.
Lochner said she watched as immigrant agents took six or seven men at an Oct. 1 ICE raid at the Monrovia Home Depot.
“So un-American,” Lochner said, as she scanned the rows of crosses. “This isn’t right.”
She added that her mom, who voted for Trump the first time, agreed with her.
“I speak up, I will not be silent,” she added.
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Lucky 13! Starship Deploys Starlink Satellites and Splashes Down Intact
SpaceX’s Starship super-rocket deployed operational next-generation Starlink satellites for the first time during its 13th flight test, which addressed snags that arose in the previous test.
The 407-foot-tall, two-stage rocket rose from its Starbase launch pad in Texas at 5:51 p.m. CT today (10:51 p.m. UTC), with all 33 Raptor engines firing on the Super Heavy booster. On the way up, the rocket set a record for maximum dynamic pressure, also known as Max-Q.
Minutes after liftoff, the Starship upper stage — known as Ship — separated to continue on the flight test’s trajectory, and then the booster relit its engines for a controlled splashdown in the Gulf of Mexico. SpaceX launch commentator Dan Huot noted that not all of the engines fired up as planned — making for a splash that was a bit spicier than expected but still safe.
During the next phase of the test, Ship sent out 20 operational Starlink V3 satellites from a deployment system that’s been nicknamed the “Pez Dispenser.” For about 20 minutes, SpaceX’s engineering team ran a series of tests to check the deployment of solar arrays and see how the satellites were able to communicate with other spacecraft in the telecom network using laser systems.
“Not only were we able to make contact with all 20, but we also made comms over lasers with all of them as well,” SpaceX engineer Kate Tice said. “So, that is awesome.”
The satellites weren’t meant to stay in orbit. After the tests were completed, all 20 re-entered the atmosphere and burned up. But the data gathered during the tests will help SpaceX ensure that future batches of Starlink V3 satellites work properly.
Starlink V3 satellites are built to download data at speeds of up to 1 terabit per second, which marks a substantial technological advance over the V2 satellites that make up the bulk of the Starlink constellation. Adding V3 satellites to the network will upgrade Starlink’s capacity for direct-to-device services.
After satellite deployment, the upper stage executed a relight of one of its six Raptor engines in mid-flight, and then descended through the atmosphere to a splashdown in the Indian Ocean. On the way down, Ship’s heat shield weathered fiery flashes of plasma that made for quite a fireworks show on the in-space video transmitted down to Earth via Starlink. At the very end, the upper stage settled down intact in the water, spouting flames as it floated.
“That is a first. That is the softest splashdown we have ever had with a Starship there in the Indian Ocean,” Huot said. “This is a dream scenario for the team that’s trying to get this heatshield data.”
This marked the second test of SpaceX’s beefed-up Starship V3 rocket. The previous test in May followed a similar flight profile and was rated a success, but SpaceX made some modifications to systems on the Super Heavy booster as well as on the upper stage to address engine performance issues.
SpaceX’s initial attempt to launch the 13th flight test was aborted a week ago, at the moment of ignition, when four Raptor engines failed to start up for launch. After the scrub, SpaceX found six booster engines that raised concerns and replaced them for today’s second try.
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