Teams at Katalyst Space are making progress slowing the spin of their LINK spacecraft, which is designed to boost the orbit of NASA’s Neil Gehrels Swift Observatory. A series of thruster burns this week reduced the rate of spin from approximately 9 degrees per second to less than 4 degrees per second. Katalyst is continuing with this approach to restabilize the spacecraft in the coming days.

Teams also further evaluated LINK’s functionality and determined there are still potential paths forward for a boost. NASA is working closely with Katalyst to consider revised, innovative approaches. The agency will continue to provide updates about stabilization of LINK and next steps for the mission. LINK is now expected to approach Swift around the end of August.

Learn more from Katalyst, and monitor NASA’s Swift blog for continued updates:

https://science.nasa.gov/blogs/swift

The post Efforts Continue to Stabilize LINK Spacecraft for NASA’s Swift Boost appeared first on NASA Science.

Scientists from the Paul Scherrer Institute (PSI), conducting a new series of experiments with millions of ultracold neutrons, have determined that the neutral particles do not switch between our universe and a theoretical “mirror universe” containing oppositely charged, identical counterparts of all elementary particles previously proposed by theoretical physicists.

Although the new experiments do not completely disprove the concept of a mirror universe, the experiments do cast doubt on one of the idea’s fundamental principles, making its existence less likely. The team behind the new study said their findings also aid future experiments by eliminating one potential area of inquiry.

Neutrons Are the Perfect Candidate to Test for a Mirror Universe

Although theoretical physicists sometimes propose radical concepts, one such idea proposes a mirror universe where every elemental particle has a “twin.” For example, the authors of the new study explain, there would be mirror protons, mirror electrons, and mirror neutrons. Still, they note, interaction between the particles in our universe and their mirror universe companions is likely to be minimal.

Geza Zsigmond, a researcher at the PSI Center for Neutron and Muon Sciences, said the theory suggests that the two mirror particles “sense each other’s presence” through gravity. Some physicists have even suggested that gravitational interaction with mirror-universe particles could explain dark matter. Unfortunately, experiments designed to hunt for the mirror universe have returned zero positive results.

Bernhard Lauss, leader of the research group for ultracold neutron physics at the PSI Center for Neutron and Muon Sciences, said, “There is no way of proving the existence of mirror particles using gravitational interaction alone.” Fortunately, the theory also offers a second testing possibility.

According to Zsigmond and colleagues, mirror universe particles would interact with our universe either through gravitation or through what they described as a “rare” oscillation of neutrons. This means that neutral particles like a neutron could occasionally disappear from our universe and reappear in the mirror universe. Even more surprisingly, the same theory says that these particles could magically return to our universe as well.

“Based on this hypothesis, neutral particles might oscillate to and fro between our normal matter world and the mirror world,” Lauss said.

The team said that this possibility, combined with new experiments at the Institut Laue-Langevin in France that “rekindled” speculation about the mirror universe, focused their new efforts on this “other” property of mirror universe particles.

Study Finds No Evidence for Neutral Particle Oscillations

After joining up with researchers from ETH Zurich and the Jagiellonian University in Kraków, the PSI team designed a series of experiments that should show if neutrons are zipping back and forth between universes. Zsigmond said that neutrons are ideal to test the concept for two reasons. First, they are neutral particles, and second, the researcher said they have a “strange property” the team hoped to exploit.

“Neutrons appear to have different lifetimes, depending on how this is measured,” Zsigmond explained.

Although several theories have been proposed to explain this discrepancy, the team acknowledged that the varying neutron lifetimes could be caused by some of these neutral particles disappearing from our universe and entering the mirror universe.

First, the team used the high-intensity proton accelerator at PSI to generate the millions of neutrons needed for their experiments. Next, the team slowed the neutrons down, creating what scientists call “ultracold” neutrons.

Next, the researchers trapped the ultracold neutrons in a specially designed non-magnetic stainless steel vacuum chamber. Because the theory suggests that the probability of neutrons jumping between universes is extremely sensitive to magnetic fields, the vacuum chamber was surrounded by magnetic field coils that the researchers could control with the required precision.

Throughout the experimentation phase, the researchers stored 1.5 million ultracold neutrons in the chamber every five minutes. After about 200 seconds, the team would empty the chamber and count how many neutrons remained. The team repeated this process over several months, resulting in the creation, storage, and measurement of approximately 25 billion neutrons.

Lauss said the researchers gradually varied the strength and direction of the magnetic field throughout the process to “scan all the relevant regions in which one might expect oscillations between neutrons and mirror neutrons to occur.” However, Lauss said, “we saw no evidence at all of such oscillations.”

Experiments “Set the Standard” For the Foreseeable Future

When discussing the significance of their findings, the PSI-led team said the lack of evidence of mirror universe oscillation by ultracold neutrons suggests a very high probability that such mirror universe neutral particle roundtrips “can be ruled out.” They also note that failing to find evidence of a mirror universe still resulted in benefits for particle physics by eliminating an area of inquiry.

“By restricting the scope for certain speculations, we are showing researchers in theoretical physics that they need to explore new avenues,” Zsigmond explained. “Physics needs that kind of impetus if it is to continue to evolve.”

Moving forward, the team said that “substantial improvements” to their experiments would require a much more elaborate setup. Until then, they said their experiment and its results are “the best of its kind in the world and will set the standard for the foreseeable future.”

The study “New High-Sensitivity Search for Neutron to Mirror-Neutron Oscillations at the PSI Ultracold Neutron Source” was published in Physical Review Letters.

Christopher Plain is a Science Fiction and Fantasy novelist and has spent the last six years as Associate News Editor and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him at christopher@thedebrief.org

An unusual clump of gas 450 million years after the Big Bang may contain stars hailing from the universe’s elusive first generation of stars. New research examines an alternative explanation involving an accreting black hole.

Meet Hebe

Initially spotted in 2024, an early-universe gas clump nicknamed Hebe has now been identified as a possible hiding place of Population III (Pop III) stars — the universe’s first generation of stars. Pop III stars are thought to be massive and chemically pristine, containing only hydrogen, helium, and a whisper of lithium. This exciting hypothesis was prompted by the detection of recombination lines from helium, which could be ionized by the high-energy radiation of the first stars.

Before the community settles on this exciting explanation, however, the hypothesis must withstand all the tests astronomers can throw at it. In a recent research article, Junehyoung Jeon, Tae Bong Jeong, and Saiyang Zhang (The University of Texas at Austin) along with Volker Bromm (The University of Texas at Austin) attempted to explain Hebe’s properties in another way.

Considering Alternatives

Hebe glows with distinctive helium emission that requires a source of high-energy radiation. This radiation could be provided by a cluster of Pop III stars, but it could also, in theory, arise from an accreting supermassive black hole embedded within the gas clump.

The authors used models to explore both possibilities. For the first scenario, in which the telltale helium emission is driven by a cluster of Pop III stars, the team calculated the maximum possible mass of the cluster, which sets how much high-energy radiation is produced. The cluster mass is moderated by high-energy radiation from another source: GN-z11, a starburst galaxy situated about 10,000 light-years from Hebe. For the second scenario, the team modeled the spectral energy distribution arising from a supermassive black hole — either a direct-collapse black hole or a primordial black hole — accreting pristine gas from the surrounding cloud.

Still a Leading Explanation

While the black hole scenario could, with reasonable black hole masses, gas densities, and accretion rates, reproduce individual flux measurements drawn from JWST observations, this hypothesis struggled to simultaneously match multiple measurements. The Pop III star cluster scenario, with a cluster mass of a few hundred thousand solar masses, provided the best fit to the JWST data.

As a final test, the team introduced a third possibility involving a population of second-generation stars, which are more chemically enriched than Pop III stars. While this model fit well, the number of stars necessary to match the data — roughly 10 million — would produce a stellar continuum detectable (but so far not seen) by JWST.

While a cluster of Pop III stars is still the leading explanation for Hebe’s properties, the team noted that the Pop III star and black hole hypotheses aren’t mutually exclusive; Hebe could very well harbor a primordial black hole and a smattering of Pop III stars. Regardless of what powers its characteristic helium emission, Hebe offers an enticing glimpse into the early universe, and more work is needed to understand this intriguing object.

Citation

“What Is Powering the Enigmatic He II Emitter Hebe: The First Stars or Black Holes?” Junehyoung Jeon et al 2026 ApJ 1006 27. doi:10.3847/1538-4357/ae7bea

The post First-Generation Stars Provide Better Fit than a Black Hole for Early-Universe Gas Clump appeared first on AAS Nova.