Category: 7. Science

SpaceX launched another batch of its Starlink broadband satellites today (Aug. 30), sending 24 of them up from California’s central coast.

A Falcon 9 rocket carrying the Starlink craft lifted off today from Vandenberg Space Force Base at 12:59 a.m. EDT (0359 GMT; 9:59 p.m. local California time on Aug. 29).

The rocket’s first stage, designated Booster 1082, came back to Earth as planned about 8.5 minutes later, touching down at sea on the SpaceX drone ship named “Of Course I Still Love You.” It was the 15th launch and landing for this particular booster, according to a SpaceX mission description.

That number, while impressive, is far from SpaceX’s reuse record of 30, which a Falcon 9 booster set this past Thursday (Aug. 28) on another Starlink mission.

Taipei, Aug. 30 (CNA) A total lunar eclipse, an astronomical event often referred to as a “blood moon,” will be visible to skywatchers in Taiwan starting around midnight on Sept. 8, the Taipei Astronomical Museum announced on Friday.

The phenomenon is also called “blood moon” due to the reddish-orange hue it takes on when the Earth passes directly between the Sun and the Moon, completely blocking direct sunlight from reaching the lunar surface.

The only light is refracted by the Earth’s atmosphere, and its red wavelengths are bent toward the Moon, illuminating it in a dramatic crimson light.

Describing the event as the most important astronomical phenomenon of 2025, the museum said the eclipse will begin at around 11 p.m. on Sept. 7 as the Moon enters the Earth’s partial shadow.

The eclipse will start at 0:27 a.m. on Sept. 8, when the Moon begins entering the Earth’s full shadow. The period of totality, when the Moon is completely in the earth’s shadow and appears dark red, will last from 1:31 a.m. to 2:53 a.m.

This will be the first total lunar eclipse fully visible from Taiwan since 2018, the museum noted, recommending that stargazers find a location with an unobstructed view of the southwestern sky for the best viewing.

In addition to the main event, the museum noted a few other celestial treats for observers.

The Beehive Cluster (Praesepe) and Venus will appear together in the night sky on Monday, and on Sept. 13, the last quarter moon will be seen near the Pleiades star cluster (Messier 45), also known as the Seven Sisters.

Have you seen comet C/2025 K1 (ATLAS) yet?

This icy visitor from the Oort Cloud is currently visible, but best seen from the Southern Hemisphere, or at the very least, southerly latitudes within the Northern Hemisphere.

It was discovered in May 2025 by the Asteroid Terrestrial-impact Last Alert System and is expected to reach perihelion, its closest point to the Sun in its orbit, on 8 October 2025.

C/2025 K1 (ATLAS) may then disintegrate, but if it survives its close passage near the Sun, it could emerge and become a bright object visible through binoculars in autumn and winter 2025.

Prolific comet-chaser and photographer José J. Chambó (www.cometografia.es) has been out photographing the comet ahead of perihelion, revealing its glowing nucleus and bright tail.

“After its first approach to Earth, I imaged comet C/2025 K1 (ATLAS) on 21 August 21 2025, when it was near the star 9 Herculis,” José says.

“In this image it shines at about magnitude +12.5, showing a greenish coma just over 2 arcminutes wide with moderate central condensation. The tail extends roughly 20 arcminutes.

“On its way to perihelion, which it will reach on 8 October 2025 at only 0.33 AU from the Sun – inside Mercury’s orbit – the comet faces a high risk of disintegration.

“If it survives, it could become observable again on its return toward Earth, in the morning sky of the Northern Hemisphere, reaching a brightness near magnitude +8 and perhaps visible with binoculars.”

For help and advice, read our guide on how to photograph a comet.

Share your comet images with us by emailing contactus@skyatnightmagazine.com

What have scientists at the University of Galway discovered this week?

They have found a baby exoplanet – a baby in chronological terms, but not in terms of size.

What is an exoplanet?

An exoplanet is a planet orbiting around another sun. They were first discovered in 1995. Since then thousands of them have been detected. There are countless billions of them in the universe. The holy grail for astronomers is to find a planet like our own in the so-called “Goldilocks zone”, where it is neither too hot nor too cold for life.

What have the scientists found?

The romantically named WISPIT 2b was discovered orbiting a new star 430 light years away in the constellation of Aquila. WISPIT 2 is a young star, which has just been formed.

Astronomers know this because it is surrounded by a multiringed disk known as a protoplanetary disk. This is material left over after a star is formed. The planets in our solar system emerged from the birth of our sun six billion years ago.

The significance of this discovery is that astronomers were able to see within this disk a planet being formed. The planet in question is a gas giant like our Jupiter or Saturn, but is many times bigger. The astronomers liken the discovery to a prehistoric time machine where one can watch the birth of a solar system like our own.

[ New ‘exceptionally beautiful’ planet discovered by Irish astronomersOpens in new window ]

How was it discovered?

Observing exoplanets is exceptionally difficult. They emit no light of their own and can usually only be detected by blocking out the light from the sun around it.

The ground-breaking discovery was made using one of the world’s most advanced observatories – the European Southern Observatory’s Very Large Telescope (ESO’s VLT) in the Atacama Desert in Chile.

The teams at Galway, Leiden University in the Netherlands and the University of Arizona took multiple photographs of the star in question to see if they could detect light reflecting from an exoplanet.

Instead they found the multiringed, multicoloured dust disk. The disk is huge stretching to 380 astronomical units (380 times the distance of the Earth from the Sun) or 5.7 trillion kilometres.

The astronomy world was amazed as this phenomenon had been detected but never seen before.

How have astronomers reacted?

Chloe Lawlor, a doctoral student at the University of Galway, summed up the excitement: “WISPIT 2b, with its position within its birth disk, is a beautiful example of a planet that can be used to explore current planet formation models. I am certain this will become a landmark paper.”

The planet was captured in near infrared light – the type of view that someone would see when using night-vision goggles – as it is still glowing and hot after its initial formation phase.

You most likely learned factorization in elementary school. You take a number and, using some known rules and some trial and error, you can work out its prime factors: the prime numbers you can multiple together to get the original number. Let’s have an example.

If I were to ask you the factors of the number 30, you would immediately know that one has to be 2, because 30 is even. To find the next factors, we would divide 30 by 2, which gives us 15. The number 15 is not prime, so we need to do the process again. There are multiple ways to find another factor. We know that numbers that end in 5 and 0 are divisible by 5. So that’s our next factor, and we are left with the number 3. The bigger the number, the more complicated and longer the process gets. Even for the most powerful computers.

Factorization is incredibly important in cryptology, the science of secure communication. The authors, Peter Gutmann and Stephan Neuhaus, are experts in the field. An encryption algorithm, for example, uses large prime numbers multiplied together to create public key components, given how difficult it is to solve such a problem.

Quantum computers have the potential to be exponentially faster at solving such problems than regular computers. But so far, that potential has not borne fruit. Algorithms have factorized 15 and 21, but failed to factorize 35, for example.

There was also the factorization of a much larger number, the so-called RSA-2048 number; it has 617 decimal digits (which I will not write here), but the team points out there was sleight of hand there too. The number is the product of two consecutive primes, and it can be solved with a square root method. Take the example of the numbers 328 and 5,183. The square root of the first is 17.92, very close to 18, the number between its two factors, 17 and 19. The square root of the second one is 71.99. No stars for guessing that its two factors are 71 and 73.

Alfredo, we were promised a dog! I’m getting to it, do not worry! Knowing that the numbers selected for these tests are chosen for how well they can be solved, the team decided to point out that they can do the same in several ridiculous ways. First, they used a computer from 1981 and an algorithm from 1945 to do the same work. Even more impressive is that you can do the same with an abacus.

But the cherry on top is the use of one of the author’s dogs: Scribble. Scribble was employed in the factorization process by barking three times, being able to find the number of factors for both 15 and 21. Obviously, we had to try this ourselves.

             

Our canine computer, Llywelyn ‘Clue’ Orpheus Carpineti, is a lot more barky than the well-behaved Scibble. We picked the number 187 to be factorized and Clue delivered 11 barks, the correct number to factorize 187. The other factor is 17. One of the points that the team raises in the paper is that the factors should be unknown to the experimenter.

Due to the sheer number of barks necessary to solve the RSA-2048 number and given that “Scribble is very well behaved and almost never barks,” the authors did not attempt to factorize that number. But they point out algorithms that you can use to have barky dogs solve even enormous numbers without the need of a huge number of barks. It all comes down to picking the right number to factorize.

The moral of the story is that quantum computing is hard. The potential of this technology is incredible, but there are many major challenges to overcome before it will be at a useful level. 

The study is available via the Cryptology ePrint Archive.

Ever wondered why the moon looks slightly different every night? This is due to where we are in the lunar cycle.

The lunar cycle is a series of eight unique phases of the moon’s visibility. The whole cycle takes about 29.5 days, according to NASA, and these different phases happen as the Sun lights up different parts of the moon whilst it orbits Earth. 

So, let’s see what’s happening with the moon tonight, Aug. 30.

What is today’s moon phase?

As of Saturday, Aug. 30, the moon phase is Waxing Crescent, and 43% will be lit up to us on Earth, according to NASA’s Daily Moon Observation.

There’s a lot to see when you look up at the moon tonight. With no visual aids, you’ll see the Mare Serenitatis, the Mare Fecunditatis, and the Mare Tranquillitatis.

With binoculars, you’ll also get a glimpse of the Endymion Crater, the Posidonius Crater, and the Mare Nectaris. If you have a telescope in your lineup, you’ll also spot the Rima Ariadaeus, Apollo 17, and the Rupes Altai.

When is the next full moon?

The next full moon will be on Sept. 7. The last full moon was on Aug. 9.

Mashable Light Speed

What are moon phases?

According to NASA, moon phases are caused by the 29.5-day cycle of the moon’s orbit, which changes the angles between the Sun, Moon, and Earth. Moon phases are how the moon looks from Earth as it goes around us. We always see the same side of the moon, but how much of it is lit up by the Sun changes depending on where it is in its orbit. This is how we get full moons, half moons, and moons that appear completely invisible. There are eight main moon phases, and they follow a repeating cycle:

New Moon – The moon is between Earth and the sun, so the side we see is dark (in other words, it’s invisible to the eye).

Waxing Crescent – A small sliver of light appears on the right side (Northern Hemisphere).

First Quarter – Half of the moon is lit on the right side. It looks like a half-moon.

Waxing Gibbous – More than half is lit up, but it’s not quite full yet.

Full Moon – The whole face of the moon is illuminated and fully visible.

Waning Gibbous – The moon starts losing light on the right side.

Last Quarter (or Third Quarter) – Another half-moon, but now the left side is lit.

Waning Crescent – A thin sliver of light remains on the left side before going dark again.

Now, two of the researchers involved — Aster Taylor of the U-M Department of Astronomy and Darryl Seligman of Michigan State University — have authored a new study starting to characterize this far-flung object, dubbed 3I/ATLAS.

Interstellar objects are born outside our solar system and cruise through it without falling into a stable orbit around the sun. 3I/ATLAS and its two predecessors have opened rare, invaluable opportunities for researchers to learn new things about distant parts of our galaxy.

“This is what we’re here for — finding objects like this, making the public aware of them and generating excitement,” said Aster Taylor, a Fannie and John Hertz Fellow in the U-M Department of Astronomy.

That public excitement, in turn, keeps momentum going for funding and the new tools to enable future discoveries. For example, the Vera C. Rubin Observatory, which is supported by the U.S. National Science Foundation and the U.S. Department of Energy, came online this summer. Although it did not discover 3I/ATLAS, it’s projected to find one or two new interstellar objects per year, Taylor said.

“It’s an auspicious time to find cool objects,” Taylor said. “We’re excited about three, but if we can get to 10 or more of these things, then we’ll have a reasonable sample and we’ll be really excited about that.”

Both reports are available as preprints on arXiv. Taylor and Seligman also authored an op-ed about the discovery for Space.com.

Tale of the tape

The discovery of 3I/ATLAS was made possible by NASA’s Asteroid Terrestrial-impact Last Alert System. ATLAS consists of four telescopes — two in Hawaii, one in Chile and one in South Africa — that automatically scan the whole sky several times every night looking for moving objects.

ATLAS’s name hints at one of the most pressing factoids about this object: It’s not going to make terrestrial impact. That is, it won’t crash into Earth. In fact, it won’t get any closer to us than we are to the sun.

Also, it’s likely a comet, Taylor said. It’s enveloped by what’s known as a coma, a fuzzy cloud of gas and dust around its rocky nucleus. As 3I/ATLAS nears the sun, that coma will likely evolve and reveal interesting clues about its composition.

“3I/ATLAS likely contains ices, especially below the surface, and those ices may start to activate as it nears the sun,” said Seligman, a postdoctoral fellow at MSU. “But until we detect specific gas emissions, like H2O, CO or CO2, we can’t say for sure what kinds of ice or how much there is.”

Over the coming months, space telescopes like Hubble and JWST will be able to zoom in on 3I/ATLAS to probe these and other questions about its size, spin and how it reacts to being heated.

“We have these images of 3I/ATLAS where it’s not entirely clear and it looks fuzzier than the other stars in the same image,” said James Wray, a professor at the Georgia Institute of Technology who was involved in the discovery. “The object is pretty far away and, so, we just don’t know.”

Still, the researchers were able to work out some important characteristics from their initial observations. Specifically, 3I/ATLAS is faster, larger and older than its predecessors, 1I/’Oumuamua and 2I/Borisov.

3I/ATLAS has a hyperbolic velocity of just under 60 kilometers per second — roughly 130,000 miles per hour — compared to 26 for ‘Oumuamua and 32 for Borisov. The diameter of 3I/ATLAS is currently estimated to be as much as 10 kilometers, or 6 miles, which would be 100 times that of ‘Oumuamua and 10 times that of Borisov.

But Taylor is confident those numbers will shrink as astronomers get better observations of 3I/ATLAS. Such a large size would imply galaxies are way more efficient at making these kinds of objects than is physically possible.

Finally, ‘Oumuamua and Borisov have ages measured in millions of years, while 3I/ATLAS appears to be between 3 billion and 11 billion years old.

“It’s a wide range,” Taylor said. “But 11 billion years is pretty old. It’s about as old as the galaxy.”

This is another number that Taylor suspects will ultimately turn out to be toward the smaller end of the range. But it will be interesting regardless because it can provide more clues about how our galaxy was forming stars, planets and other objects earlier in its history.

The discovery

Taylor was recruited for the project while traveling to help confirm 3I/ATLAS was an interstellar object and make early characterizations. And there was a time crunch. If the ATLAS team had noticed 3I, odds were other astronomers had, too, and the team wanted to confirm its suspicions and get the news out first.

“I was fully on vacation in Fiji with my family when this was announced. When I heard, I just thought, ‘All right. Well, that’s my next two days,’” Taylor said. “It’s very exciting, but it’s also more stressful than you might think.”

Seligman had a little bit more notice, but not much. News started to spread within the group on July 1.

“I heard something about the object before I went to bed, but we didn’t have a lot of information yet,” Seligman said. “By the time I woke up around 1 a.m., my colleagues, Marco Micheli from the European Southern Observatory and Davide Farnocchia from NASA’s Jet Propulsion Laboratory, were emailing me that this was likely for real. I started sending messages telling everyone to turn their telescopes to look at this object.”

Larry Denneau, a member of the ATLAS team, reviewed and submitted the discovery observations from the European Southern Observatory’s Very Large Telescope in Chile shortly after it was observed.

“We have had false alarms in the past about interesting objects, so we know not to get too excited on the first day,” Denneau said. “But the incoming observations were all consistent, and late that night it looked like we had the real thing.”

John Tonry, another member of ATLAS and professor at the University of Hawaii, was instrumental in the design and construction of ATLAS, the survey that discovered 3I.

“It’s really gratifying every time our hard work surveying the sky discovers something new, and this comet that has been traveling for millions of years from another star system is particularly interesting,” he said.

Once 3I/ATLAS was confirmed, Seligman and Karen Meech, faculty chair for the Institute for Astronomy at the University of Hawaii, both managed the communications flow and worked on getting the data pulled together for submitting the paper.

“Once 3I/ATLAS was identified as likely interstellar, we mobilized rapidly,” Meech said. “We activated observing time on major facilities like the Southern Astrophysical Research Telescope and the Gemini Observatory to capture early, high-quality data and build a foundation for detailed follow-up studies.”

Other contributors to this research include the European Space Agency Near-Earth Objects Coordination Centre in Italy, California Institute of Technology, Auburn University, Universidad de Alicante in Spain, Universitat de Barcelona in Spain, European Southern Observatory in Germany, Villanova University, Lowell Observatory, University of Maryland, Las Cumbres Observatory, University of Belgrade in Serbia, Politecnico di Milano in Italy, University of Western Ontario in Canada, Universidad Diego Portales, Santiago in Chile and Boston University.

Like bees breathing life into gardens, providing pollen and making flowers blossom, little cellular machines called mitochondria breathe life into our bodies, buzzing with energy as they produce the fuel that powers each of our cells. Maintaining mitochondrial metabolism requires input from many molecules and proteins-some of which have yet to be discovered.

Salk Institute researchers are taking a closer look at whether mitochondria rely on microproteins-small proteins that have been difficult to find and, consequently, underestimated for their role in health and disease. In their new study, a microprotein discovered just last year at Salk, called SLC35A4-MP, was found to play a critical role in upholding mitochondrial structure and regulating metabolic stress in mouse fat cells. The findings plant the seed for future microprotein-based treatments for obesity, aging, and other mitochondrial disorders.

The study, published in Science Advances on August 29, 2025, is part of a series of recent discoveries at Salk that showcase the functional importance of microproteins in cellular biology, metabolism, and stress.

“Microproteins have long been dismissed as random genetic junk, but our work adds to a growing body of research demonstrating that many of them are actually crucial regulators of cell physiology,” says senior author Alan Saghatelian, professor and Dr. Frederik Paulsen Chair at Salk. “Here we reveal that a microprotein is responsible for preserving mitochondrial structure and function in brown fat tissue, which regulates body temperature and energy balance.”

In the late spring of 2024, Saghatelian’s lab discovered the genetic code for SLC35A4-MP hidden in an upstream open reading frame on a strand of messenger RNA (mRNA). The longstanding belief was that each mRNA strand codes for a single protein-a one-to-one ratio of mRNA-to-protein, always. So, when scientists found additional sections of genetic material- upstream open reading frames-on mRNA strands, they thought they must be either 1) random noncoding junk or 2) regulatory code that influences the translation of that mRNA.

But as genetic probing and sequencing technology became more sophisticated, researchers soon realized some of those upstream open reading frames coded for functional microproteins. This discovery brought an entirely new dimension to cellular life, as microproteins long hidden in disregarded upstream open reading frames are now in full bloom-ready to be plucked and studied.

Some of the first functional microproteins to be described were involved in metabolism and mitochondrial regulation. This includes Saghatelian’s 2024 study, in which the lab first discovered SLC35A4-MP in the walls of mitochondria. Further tests suggested the microprotein might be helping maintain healthy cellular metabolism.

But these findings were based on data collected from biochemical assays in test tubes and cells cultured in petri dishes. To fully confirm and describe SLC35A4-MP’s physiological role, they would have to test its function in a living system.

“SLC35A4-MP is among the first microproteins to be functionally characterized in mice,” says first author Andréa Rocha, a postdoctoral researcher in Saghatelian’s lab. “Indeed, we found that SLC35A4-MP regulates mitochondrial function and lipid metabolism in mice, which really goes to show that microproteins cannot be overlooked as we search for biological factors that regulate health.”

To classify SLC35A4-MP, the researchers looked at an exemplary metabolic tissue that works its mitochondria especially hard: brown fat. Brown fat cells are metabolically demanding, as they regulate energy balance and body temperature. The researchers removed SLC35A4-MP entirely from mouse brown fat cells, then induced metabolically stressful events like cold exposure or a high-fat diet.

Without SLC35A4-MP, mice were unable to dial up their metabolism during cold exposure. Their mitochondria were structurally compromised, enlarged, dysfunctional, and inflamed. Outside of the mitochondria, other parts of the brown fat cells were also affected. The researchers saw signs of cell interior remodeling and further inflammation-trademarks of metabolic decline in obesity-related conditions.

The findings demonstrate the fundamental role SLC35A4-MP plays in regulating brown fat cell function and response to metabolic stress. And because mitochondria, our buzzing cellular bees, are in every cell type in the body, the findings extend everywhere, too. SLC35A4-MP could be a powerful therapeutic target for any disease or disorder that impacts metabolic and mitochondrial function, from obesity to aging and beyond.

Microprotein research is finally springing to life, and the team sees bright blooms ahead in the search for more functional microproteins.

“As scientists have been able to add more microproteins to our protein databases, the question has remained, do these microproteins have any physiological relevance?” says Saghatelian. “And our study says yes, they are important physiological regulators. I hope that adds more fuel to the study of microproteins moving forward.”

Other authors include Antonio Pinto, Jolene Diedrich, Huanqi Shan, Eduardo Vieira de Souza, Joan Vaughan, and Mark Foster of Salk; Christian Schmedt of Novartis Research Foundation and Integrate Bioscience; Guy Perksin and Mark Ellisman of UC San Diego; Kaja Plucińska and Paul Cohen of Rockefeller University; and Srinath Sampath of Novartis Research Foundation and UC San Diego.

The work was supported by the National Institutes of Health (P30 CA014195, R01 GM102491, U24 NS120055, R01 NS108934, R01 GM138780, R01 AG065549, S10 OD021784, RC2 DK129961, NIA R01 AG081037, NIA R01 AG062479, NIMH RF1 MH129261, NIH-NCI CCSG P30 CA014195, NIH-NIA San Diego Nathan Shock Center P30 AG068635, NIH-NIA Alzheimer’s Disease Research Center P30 AG062429), National Science Foundation (2014862), American Heart Association Allen Initiative, California Institute for Regenerative Medicine, Henry L. Guenther Foundation, Helmsley Charitable Trust, and George E. Hewitt Foundation for Medical Research.

Symmetry in crystal structures plays a pivotal role in determining emergent phenomena in condensed matter systems, including unique electronic band structures with robust spin-momentum locking^1,2,3, time-reversal symmetry broken states^4,5, and topological swirling spin textures known as magnetic skyrmions⁶. Skyrmions have garnered significant attention for their potential applications in spintronic devices. Their helicity is highly dependent on the symmetry of their host material⁷. Known bulk skyrmion hosts include MnSi⁸, FeGe⁹, Fe_1−xCo_xSi¹⁰, and Cu₂OSeO₃^11,12, which crystallize in the cubic P2₁3 space group, as well as GaV₄(S/Se)₈ in R3m^13,14 and VOSe₂O₅ in P4cc ¹⁵. In these systems, the stabilization of the multiple-q skyrmion lattice (SkL) phase originates from the Dzyaloshinskii-Moriya interaction (DMI) within the helimagnetic ground state, a consequence of the relativistic spin–orbit coupling^16,17. Notably, skyrmions in P2₁3 systems are of the Bloch type, whereas in hosts with R3m symmetry, Néel-type skyrmions are observed.

Among these hosts, Cu₂OSeO₃ stands out as the first insulating material in which skyrmions were experimentally discovered. Its insulating nature enables electric-field manipulation of the SkL phase^{18,19,20,21,22}, a property complemented by other phenomena such as the stabilization of an independent SkL phase at low temperature^23,24 and novel magnetic and functional behaviors^25,26,27,28. Under high pressure, Cu₂OSeO₃ undergoes a series of structural phase transitions: first to an orthorhombic P2₁2₁2₁ phase, then to a monoclinic P2₁ structure, and finally to a triclinic P₁ polymorph^29,30. Remarkably, pressure has been shown to extend the stability range of the SkL phase up to room temperature³⁰. These attributes make Cu₂OSeO₃ a model system for advancing skyrmion physics. Recent studies have also demonstrated that when skyrmion hosts are confined in nanoparticles, approaching the size of a single skyrmion, the magnetic phase diagram is significantly altered, leading to modifications of the topological spin textures existing in bulk crystals and even lead to the emergence of novel ones^31,32,33,34. However, due to the finite spin–lattice coupling in the aforementioned SkL hosts, it is imperative to discuss the underlying crystal structure, especially while the particle size approaches the diameter of a single isolated skyrmion.

In this work, we present the discovery of a new polymorph of Cu₂OSeO₃. Through detailed crystallographic studies and density functional theory calculations, we show that this novel polymorph crystallizes in the trigonal space group R3m, belonging to the same C_3v point group symmetry than the Néel-type skyrmions hosts GaV₄(S/Se)₈. This structural change suggests that size effects could potentially drive a transformation from Bloch-type to Néel-type skyrmions in Cu₂OSeO₃. Our findings offer a possible alternate explanation for the unexpected observations of Néel-type skyrmions at the surfaces of bulk Cu₂OSeO₃ crystals³⁵.

For this study, bulk and few hundred micron sized single crystals were grown by chemical vapor transport. They were characterized using X-ray diffraction (XRD). Fifty single crystals exhibited a chiral enantiopure structure, with equal distribution between “right-handed” (denoted as I) and “left-handed” (denoted as I’) enantiomorphs. Both conform to the chiral space group P2₁3, with structure I matching prior reports on Cu₂OSeO₃ structure^7,36. No new polymorph was found in single crystals with size down to few tens of microns. Cu₂OSeO₃ nanoparticles were synthesized via a wet chemical process. Their crystal structure was determined using electron diffraction (ED) (Fig. 1a).

Of the ten analyzed nanoparticles, eight consisted of twins combining both enantiomorphs, typically comprising ~ 80% of I and ~ 20% of I’ (Fig. 1b). Two nanoparticles displayed F-centered cubic unit cell (Fig. 1c), with lattice parameters a = 8.893(5)Å (Table 1). The corresponding structure (denoted as II) was refined in the trigonal space group R3m (nonstandard F3m) with twinning along the twofold axes (100), (010), and (001) of the cubic basis (Fig. 1e). Refinement yielded R_1obs = 0.0862 and wR_all = 0.0656. To assess the stability of the trigonal structure II, density functional theory (DFT) calculations were performed within the generalized gradient approximation (GGA). The results yielded relatively small Hellmann–Feynman forces, suggesting that the structure is close to a local energy minimum. This was further validated by a direct structural optimization, using the experimental unit cell parameters and internal atomic coordinates as input. The total GGA energy of the optimized R3m phase was found to be approximately 0.8 eV/f.u. higher than that of the cubic P2₁3 phase. However, surface effects, prominent in nanoparticles, cannot be accounted in the DFT calculations but could significantly alter the energy balance and stabilize the R3m phase. Detailed refinement parameters and characteristics of structure II are provided in Tables S1, S2 and S3. Atomic positions and interatomic parameters of the trigonal phase II obtained by refinement of the ED data and by DFT are compared in Table 2 and Table S4, respectively.

All three structures I, I’ and II contain a similar substructure unit with Cu₂OSe composition and which has a cubic symmetry with the F-43m space group. Cu₂OSeO₃ is obtained by adding two O sites with half occupancy (half-filled pink circles in Fig. 1f). Based on this structural similarity, a prototype model of the ambient-pressure Cu₂OSeO₃ structure is proposed. The prototype is constructed from the substructure unit and the two additional O-sites (Fig. 1f and Table S5). However, this leads to unacceptably long Se-O distances of 2.23 Å (Table S3). These structure anomalies may be resolved by reducing the structure symmetry in two ways: (i) from F-43m to P2₁3 characteristic of I and I’ (Fig. 1d) or (ii) from F-43m to R3m_trigonal = F3m_cubic characteristic of II (Fig. 1e). During the refinement, the Se–O distances decrease to an acceptable 1.70 ± 0.01 Å in both cases (Table S3). We attribute the difference in the crystal structure to the size of the nanoparticles. Indeed, the crystals showing the I–I’ twinned structure are well-formed nanoparticles as indicated by the rather bright experimental reflections with a low background (Fig. 1b). The crystals exhibiting the structure II are characterized by weaker and split experimental reflections with a much lower intensity (Fig. 1c), indicating smaller attached nanoparticles. Unlike the pure enantiomorph bulk crystals grown from a single nucleus, multiple nucleation centers form during the synthesis process after selenious acid leaching from CuSeO₃·2H₂O precursor. This leads to nanoparticles with multiple twinning. The smaller particle size observed in the R3m polymorph suggests the existence of a critical size threshold below which the cubic form of Cu₂OSeO₃ cannot be stabilized. This hypothesis warrants further investigation.

Figure 2 illustrates both the similarities and differences among the three structural forms of Cu₂OSeO₃. The fundamental building unit consists of two corner-sharing oxygen-centered tetrahedrons, forming structural [O₂Cu₇] dimers ⁷. Across all structures, the interatomic distances and Cu–O–Cu bond angles remain comparable (see Table S3 in the Supplementary Information). In the cubic structure, these [O₂Cu₇] dimers exhibit ferrimagnetic ordering, with Cu1 and Cu2 carrying opposing magnetic moments. In all structures, including the prototype (Fig. 2b), the structural dimers are arranged in hexagonal rings oriented perpendicular to the threefold axis along the four diagonals of the cubic lattice (Figs. 2c-d). Similar hexagonal arrangements appear in the trigonal lattice along the (001) plane, as well as the (021), (-221), and (2–21) planes (Fig. 2e). However, the arrangement of the [O₂Cu₇] dimers within these hexagonal rings differs between the cubic and trigonal structures. In the cubic structure, hexagons consist of alternating O1-Cu1-O3 and O3-Cu2-O1 bonds (Figs. 2c-d), whereas in the trigonal structure, they are built with six O1-Cu2-O4 bonds, with O4-Cu1-O1 acting as bridges along the threefold symmetry axis (Fig. 2e). The distinct arrangement of dimers in the trigonal structure, as compared to the cubic phase, suggests a different magnetic ordering and hierarchy of energy scales, which may give rise to fundamentally different magnetic structures in the trigonal polymorph.

In the cation-centered polyhedral representation (Fig. 3), Cu1 and Cu2 are positioned within a trigonal bipyramid and a tetragonal pyramid, respectively. The Cu2-centered tetragonal pyramids differ between the two structures in terms of Cu–O interatomic distances: in the cubic structure, the apical Cu–O bond is longer than the equatorial ones, whereas in the trigonal structure, all five Cu–O distances are similar. Although the Cu1- and Cu2-containing polyhedra share edges and follow a similar arrangement (Fig. 3a), the connectivity of Cu2-centered polyhedra varies due to differences in the positioning of SeO₃ groups. In the cubic lattice, these tetragonal pyramids contribute to a three-dimensional framework, while in the trigonal structure, they form a flat triangular arrangement (Fig. 3b). Consequently, the trigonal polymorph of Cu₂OSeO₃ exhibits a layered-like structural organization (Fig. 3b).

This structural distinction may help explain a previously unpredicted observation reported by Zhang et al³⁵. who used resonant elastic X-ray scattering (REXS) at the Cu–L₂ absorption edge. At this energy, the X-ray penetration depth is limited to only a few tens of nanometers which is the size range of the Cu₂OSeO₃ nanoparticles studied here. The unexpected Néel-type swirls observed at the surface of bulk Cu₂OSeO₃ could be attributed to a local symmetry lowering, potentially reflecting the trigonal structure similar to the one discussed in this work. While our single-crystal XRD results rule out the presence of the R3m polymorph in the bulk, they do not preclude the possibility of this lower-symmetry phase existing at the surface.

In conclusion, this study reveals the discovery of a new polymorph of Cu₂OSeO₃, observed exclusively in nanoparticles. Electron diffraction based crystallographic analysis and DFT calculations confirm its R3m space group. While both trigonal and cubic polymorphs share a [O₂Cu₇] dimer-based framework, differences in SeO₃ positioning result in distinct connectivity between Cu-centered polyhedra, leading to a layered-like structure in the trigonal phase. The trigonal polymorph exhibits C_3v symmetry, like Néel-type skyrmion hosts, suggesting that size effects may drive a transformation from Bloch-type to Néel-type skyrmions in Cu₂OSeO₃. This discovery opens several promising directions for future research. First and foremost is the development of synthesis methods or deposition protocols capable of producing phase-pure trigonal nanoparticles or thin films. Such samples would allow precise determination of the stoichiometry of the trigonal phase, either confirming the composition deduced from structural analysis or revealing an off-stoichiometry required to stabilize this polymorph. They would also enable the investigation of skyrmion behavior under C_3v symmetry in Cu₂OSeO₃. If successful, this would open the door to a range of studies, including the identification of a cycloidal magnetic ground state, the emergence of a field-induced Néel-type skyrmion lattice, potential magnetoelectric coupling, electric-field-driven skyrmion dynamics, and the collective behavior of magnon modes in the microwave regime.

Scientists have discovered a clever new way to control the light emitted by quantum dots — tiny crystals that can release individual photons.

The advance could lead to faster, cheaper, and more practical quantum technologies, from ultra-secure communication systems to experiments that explore the strange foundations of quantum physics.

The Challenge of Single-Photon Sources

Quantum dots are tiny semiconductor structures capable of releasing single photons on demand, making them strong candidates for future photonic quantum computers. The difficulty is that no two quantum dots are exactly the same, and each can emit light at slightly different colors. This variation prevents researchers from combining multiple dots to create multi-photon states.

To work around this, scientists typically rely on a single quantum dot and then split its light into different spatial and temporal modes with the help of a fast electro-optic modulator. The drawback is that these modulators are costly, often require highly customized designs, and can be inefficient, leading to energy losses within the system.

An Elegant Optical Solution Emerges

A research collaboration led by Vikas Remesh of the Photonics Group at the Department of Experimental Physics, University of Innsbruck, together with partners from the University of Cambridge, Johannes Kepler University Linz, and other institutions, has now demonstrated a way to bypass these challenges. Their method relies on a fully optical process known as stimulated two-photon excitation. This technique allows quantum dots to emit streams of photons in distinct polarization states without the need for electronic switching hardware.

In tests, the researchers successfully produced high-quality two-photon states while maintaining excellent single-photon characteristics.

How the Technique Works in Practice

“The method works by first exciting the quantum dot with precisely timed laser pulses to create a biexciton state, followed by polarization-controlled stimulation pulses that deterministically trigger photon emission in the desired polarization,” explain Yusuf Karli and Iker Avila Arenas, the study’s first authors.

“It was a fantastic experience for me to work in the photonics group for my master’s thesis, remembers Iker Avila Arenas, who was part of 2022-2024 cohort of the Erasmus Mundus Joint Master’s program in Photonics for Security Reliability and Safety and spent 6 months in Innsbruck.

Moving Complexity to the Optical Stage

“What makes this approach particularly elegant is that we have moved the complexity from expensive, loss-inducing electronic components after the single photon emission to the optical excitation stage, and it is a significant step forward in making quantum dot sources more practical for real-world applications,” notes Vikas Remesh, the study’s lead researcher.

Looking ahead, the researchers envision extending the technique to generate photons with arbitrary linear polarization states using specially engineered quantum dots.

Real-World Quantum Applications

“The study has immediate applications in secure quantum key distribution protocols, where multiple independent photon streams can enable simultaneous secure communication with different parties, and in multi-photon interference experiments which are very important to test even the fundamental principles of quantum mechanics,” explains Gregor Weihs, head of the photonics research group in Innsbruck.

The research, published in npj Quantum Information, represents a collaborative effort involving expertise in quantum optics, semiconductor physics, and photonic engineering.

Reference: “Passive demultiplexed two-photon state generation from a quantum dot” by Yusuf Karli, Iker Avila Arenas, Christian Schimpf, Ailton Jose Garcia Junior, Santanu Manna, Florian Kappe, René Schwarz, Gabriel Undeutsch, Maximilian Aigner, Melina Peter, Saimon F. Covre da Silva, Armando Rastelli, Gregor Weihs and Vikas Remesh, 11 August 2025, npj Quantum Information.
DOI: 10.1038/s41534-025-01083-0

The work was supported by the Austrian Science Fund (FWF), the Austrian Research Promotion Agency (FFG), and the European Union’s research programs.

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