NASA’s Fermi Spots Young Star Cluster Blowing Gamma-Ray Bubbles - UNIVERSE

For the first time, astronomers using NASA’s Fermi Gamma-ray Space Telescope have traced a budding outflow of gas from a cluster of young stars in our galaxy — insights that help us understand how the universe has evolved as NASA explores the secrets of the cosmos for the benefit of all.

The cluster, called Westerlund 1, is located about 12,000 light-years away in the southern constellation Ara. It’s the closest, most massive, and most luminous super star cluster in the Milky Way. The only reason Westerlund 1 isn’t visible to the unaided eye is because it’s surrounded by thick clouds of dust. Its outflow extends below the plane of the galaxy and is filled with high-speed, hard-to-study particles called cosmic rays.

“Understanding cosmic ray outflows is crucial to better comprehending the long-term evolution of the Milky Way,” said Marianne Lemoine-Goumard, an astrophysicist at the University of Bordeaux in France. “We think these particles carry a large amount of the energy released within clusters. They could help drive galactic winds, regulate star formation, and distribute chemical elements within the galaxy.”

A paper detailing the results published Dec. 9 in Nature Communications. Lemoine-Goumard led the research with Lucia Härer and Lars Mohrmann, both at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany.

This image of super star cluster Westerlund 1 was captured with the Near-InfraRed Camera on NASA’s James Webb’s Space Telescope. The cluster is largely hidden at visible wavelengths by dust clouds, which infrared light penetrates. Westerlund 1’s large, dense, and diverse stellar population of massive stars has no other known counterpart in the Milky Way.

ESA/Webb, NASA & CSA, M. Zamani (ESA/Webb), M. G. Guarcello (INAF-OAPA) and the EWOCS team

Super star clusters like Westerlund 1 contain more than 10,000 times our Sun’s mass. They are also more luminous and contain higher numbers of rare, massive stars than other clusters.

Scientists think that supernova explosions and stellar winds within star clusters push ambient gas outward, propelling cosmic rays to near light speed. About 90% of these particles are hydrogen nuclei, or protons, and the remainder are electrons and the nuclei of heavier elements.

Because cosmic ray particles are electrically charged, they change course when they encounter magnetic fields. This means scientists can’t trace them back to their sources. Gamma rays, however, travel in a straight line. Gamma rays are the highest-energy form of light, and cosmic rays produce gamma rays when they interact with matter in their environment.

Most gamma-ray observations of stellar clusters have limited resolution, so astronomers effectively see them as indistinct areas of emission. Because Westerlund 1 is so close and bright, however, it’s easier to study.

In 2022, scientists using a group of telescopes in Namibia operated by the Max Planck Institute called the High Energy Spectroscopic System detected a distinct ring of gamma rays around Westerlund 1 with energies trillions of times higher than visible light.

Lemoine-Goumard, Härer, and Mohrmann wondered if the cluster’s unique properties might allow them to see other details by looking back through nearly two decades of Fermi data at slightly lower energies — millions to billions of times the energy of visible light.

Fermi’s sensitivity and resolution allowed the researchers to filter out other gamma-ray sources like rapidly spinning stellar remnants called pulsars, background radiation, and Westerlund 1 itself.

What was left was a bubble of gamma rays extending over 650 light-years from the cluster below the plane of the Milky Way. That means the outflow is about 200 times larger than Westerlund 1 itself.

Data from NASA’s Fermi Gamma-ray Space Telescope reveal the budding gas bubble of star cluster Westerlund 1. Brighter colors indicate a stronger likelihood that gamma rays arise from specific types of point sources, notably two pulsars located at center and in the brightest portion of the image. Pink contours denote steep changes in likelihood. An underlying orange-magenta feature extends down the image, starting from the cluster’s location, and represents the nascent outflow. The grey lines indicate distance below the galactic plane. The bubble is over 650 light-years long and angles slightly away from us. Westerlund 1’s stellar activity more easily pushes gas outward into lower-density regions of the galaxy’s disk.

NASA's Goddard Space Flight Center/Lemoine-Goumard et al. 2025; ESA/Webb, NASA & CSA, M. Zamani (ESA/Webb), M. G. Guarcello (INAF-OAPA) and the EWOCS team

The researchers call this a nascent, or early stage, outflow because it was likely recently produced by massive young stars within the cluster and hasn’t yet had time to break out of the galactic disk. Eventually it will stream into the galactic halo, the hot gas surrounding the Milky Way.

Westerlund 1 is located slightly below the galactic plane, so the researchers think the gas expanded asymmetrically, following the path of least resistance into a zone of lower density below the disk.

“One of the next steps is to model how the cosmic rays travel across this distance and how they create a changing gamma-ray energy spectrum,” Härer said. “We’d also like to look for similar features in other star clusters. We got very lucky with Westerlund 1, though, since it’s so massive, bright, and close. But now we know what to look for, and we might find something even more surprising.”

“Since it started operations 17 years ago, Fermi has continued to advance our understanding of the universe around us,” said Elizabeth Hays, Fermi’s project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “From activity in distant galaxies to lightning storms in our own atmosphere, the gamma-ray sky continues to astound us.”

By Jeanette Kazmierczak
NASA’s Goddard Space Flight Center, Greenbelt, Md.  

Source: NASA’s Fermi Spots Young Star Cluster Blowing Gamma-Ray Bubbles - NASA Science  

Neptunium study yields plutonium insights for space exploration - Energy & Green Tech

Credit: Pixabay/CC0 Public Domain

Researchers at the Department of Energy's Oak Ridge National Laboratory are breathing new life into the scientific understanding of neptunium, a unique, radioactive, metallic element—and a key precursor for production of the plutonium-238, or Pu-238, that fuels exploratory spacecraft.

The ORNL team's research arrives during a period of increased national interest in the use of Pu-238 in radioisotope thermoelectric generators, or RTGs. Often used in space missions such as NASA's Perseverance Rover for long-term power, RTGs convert heat from radioactive decay into electricity. Advancing RTG knowledge and application possibilities also requires the same high-level evaluation of both chemical reactions and structural characterization, two key aspects of the materials science for which ORNL is known.

"When people want to do scientific experiments in space, they need something to power their instruments, and plutonium is typically the power source because things like solar and lithium ion batteries don't withstand deep space," said Kathryn Lawson, radiochemist in ORNL's Fuel Cycle Chemical Technology Group and lead author of the new study.

"Plutonium is the solution, so the more scientific inquiry there is to go on a spacecraft, you need to have these types of batteries," said Lawson. "The demand always exceeds our supply. Hence, we need to have a great understanding of neptunium chemistry to support that production of Pu-238."

The team's findings, which illuminate important chemical and structural aspects of neptunium, were discovered through thermal decomposition—or by breaking down neptunium samples with heat—helping scientists to identify critical intermediate phases and guide more precise thermal treatments to discover additional neptunium insights.

The research is published in the journal Inorganic Chemistry Frontiers.

At ORNL, this and other modern characterization techniques provide useful data on neptunium's chemistry, helping advance the lab's Pu-238 production process. A critical radioisotope for use in space exploration is being produced at ORNL.

Neptunium is an important precursor of Pu-238, meaning it participates in a nuclear reaction that eventually results in Pu-238. Unlocking neptunium's complex secrets for a better understanding of its chemistry will enable more efficient, effective Pu-238 production. By improving how we understand and work with neptunium, ORNL is helping to ensure a secure, domestic supply chain for this mission-critical material, while fueling deep space exploration and advancing U.S. energy independence.

In the early 1980s, ORNL designed the original thermal decomposition process for uranium analysis. Today, Lawson and her colleagues across the lab are deploying the method to break down neptunium samples with steadily increasing heat, from 150 to 600 degrees Celsius—302 to 1,112 degrees Fahrenheit—and using multiple measurement techniques to analyze the resulting chemical reactions.

By integrating the results from each categorization and measurement technique—including Raman spectroscopy, which bombards samples with lasers to examine molecular vibrations, and computational modeling, which offers a mathematic comparison point against the team's scaled experiments—the researchers discovered new mechanistic and materials chemistry information. Including the first detailed Raman fingerprint of a key neptunium oxide, these findings help advance a general understanding of neptunium while improving the lab's specific process for Pu-238 production.

"My group and I were looking at this from a structural point of view, to help understand the decomposition mechanism. Essentially, what we do is use Raman spectroscopy to shoot lasers at the sample and excite different vibrations in the structure of the material," said nuclear security scientist Tyler Spano of ORNL's Materials and Chemistry Group, a contributing researcher to the recently published study.

"What comes out is a series of peaks, a spectrum. That tells us something about the current material structure, but what we did was follow the heating pathway that Kathryn [Lawson] uses for the material," said Spano. "We made these measurements as we were heating the material, so we could see how the chemical bonding environments were changing as we increased the temperature."

The study reunited a familiar cohort of early-career staff spanning three research directorates at ORNL, including National Security Sciences, Fusion and Fission Energy and Science, and Isotope Sciences and Enrichment. Now colleagues and collaborators at ORNL, Spano and Lawson met more than a decade ago at the University of Notre Dame, when Spano served as Lawson's graduate teaching assistant, and they worked side by side in the same university research lab. In 2020, they were reunited when Lawson joined Spano at ORNL.

"I had started a couple years before that and was so excited when Kathryn started," said Spano. "Our community is small, and the pool of people who have the expertise that you can work with in this field is so limited. It's exciting to know that someone else who thinks literally about science and the important questions is going to be here."

Lawson, Spano and their ORNL colleagues and collaborators on neptunium research are contributing to the history of understanding radioactive, metallic elements, or actinides, such as uranium, neptunium and plutonium. Meanwhile, they're adding to the resurgence of interest in neptunium's possibilities for advancing Pu-238 science.

"We're already working on our next project. It's again very basic-science-focused, and we're looking at the decomposition of some other neptunium compounds," said Lawson. "Essentially, we've figured out that we have these capabilities, and so we're looking at a number of other poorly understood neptunium compounds that are all going to be potentially of interest for Pu-238 production."

Together, Lawson, Spano and their fellow early-career researchers are helping to reinvigorate the study of neptunium chemistry and contributing to a shared understanding of the natural world, even though naturally occurring neptunium is exceedingly rare.

"It's so fun to get to research with your friends. It's all in the family," said Spano. "There are so few people who do this type of research. We all know each other, and it's just really beneficial to work together and pool our resources and capabilities."

At a place like ORNL, that unique collection of people and capabilities can yield important innovations in energy research and scientific discovery.

"This work is fun because it supports RTGs, and that side of things really captivates people when they talk about space," said Lawson. "That's what I get to tell my family: I make batteries for space. That's the nutshell. Making the best and the most batteries for space, so that we can continue to explore our solar system." 

Provided by Oak Ridge National Laboratory  

by Chris Driver, Oak Ridge National Laboratory

edited by Stephanie Baum, reviewed by Andrew Zinin 

Source: Neptunium study yields plutonium insights for space exploration