Just a few years ago, a strange signal was received from the plane of the Milky Way.

It was something astronomers had never seen before, pulsing with a radio beat too slow to fit any known astronomical object.

It may have just come and gone as a one-off anomaly.

But then they found another one.

And another.

To date, around a dozen of these long-period radio transients (LPTs) have been detected from diverse corners of the galaxy, leaving scientists baffled.

Now, a team led by astronomer Kovi Rose of the University of Sydney in Australia thinks they may finally have found their Rosetta Stone, the object that could help them interpret at least some of these weird, pulsating objects.

In the direction of the galaxy's inner regions, the researchers traced an LPT signal directly to a magnetic cataclysmic variable star – a strongly magnetized white dwarf cannibalizing its companion and belching periodic radiation.

"Long-period radio transients have puzzled astronomers for years," Rose says.

"We've only found about a dozen, and their origins have been unclear. Now, we've been able to show that the source for one of these transients comes from a white dwarf actively pulling material from a companion star."

The mystery of the LPTs, first detailed in a 2022 paper, reared its head again after astronomers found something in the plane of the Milky Way pulsing in a weird way.

Every 18.18 minutes, the brightness of an object named GLEAM-X J162759.5−523504.3 increased for 30 to 60 seconds, temporarily making it one of the brightest objects in the low-frequency radio sky.

Then it stopped.

But it wasn't long before astronomers found more – showing that, whatever this strange object was, it wasn't just a one-off weirdness.

As the population grew, astronomers began to piece together possible explanations.

Some observations pointed to highly magnetized white dwarfs, while others hinted that at least some LPTs might arise in binary systems, where a white dwarf interacts with a companion star.

A major breakthrough came in 2025, when one LPT signal, named ILT J1101+5521, was traced to a binary star consisting of a red dwarf and a white dwarf, orbiting so closely together that their magnetic fields repeatedly clashed, sending out periodic bursts of radio waves.

The picture grew even more complicated when astronomers discovered that one LPT, ASKAP J1832-0911, also emitted X-rays, suggesting energetic processes beyond radio emission alone.

But no single object seemed capable of tying all the clues together.

And that's what makes this new discovery so intriguing. Its name is ASKAP J1745-5051, and it's the first object to unite many of the puzzle pieces previously observed in other LPTs.

That includes both radio and X-ray emission, a white dwarf and a binary companion, strong magnetic activity, orbital motion, and accretion – the gravitational transfer of material onto the white dwarf.

"Some similar objects had been linked to binary systems before, but this is the first one where we can clearly see both stars and the accretion process in action," says astrophysicist Tara Murphy of the University of Sydney and the ARC Center of Excellence for Gravitational Wave Discovery (OzGrav).

The discovery was made using CSIRO's ASKAP radio telescope in Wajarri Yamaji Country in Western Australia – one of the world's most sensitive facilities.

Because the system is such a chaos gremlin, it's impossible to tell exactly how far away it is. The best estimates place it between around 1,300 and 30,000 light-years away.

But the data were detailed enough that the researchers could figure out what kind of object it is.

ASKAP observations show a system that flares in radio waves every 81 minutes (1.35 hours), accompanied by matching periodic X-ray emission detected by NASA's Swift observatory and the Einstein Probe X-ray Telescope.

Optical observations obtained using the Southern Astrophysical Research (SOAR) Telescope showed a white dwarf binary at the emission's location in the sky, with spectra revealing a clear orbital period of about 81 minutes – closely matching the period of the radio and X-ray bursts.

These observations reveal that the object is a magnetic cataclysmic variable. Every orbit, the white dwarf pulls material from its red dwarf companion star, which is funneled by the white dwarf's magnetic field onto its surface.

As the material crashes onto the white dwarf, it heats to millions of degrees and emits high-energy radiation – that's the source of the X-ray signal.

Related: Mystery Signals May Be Coming From One of The Rarest Stars in The Galaxy

Meanwhile, gas accelerated by the two stars' clashing magnetic fields appears to produce the radio signal, similar to the mechanism proposed for ILT J1101+5521.

It's such a beautiful convergence of characteristics that it could help explain other LPTs that only show some of these traits.

And it's genuinely exciting to be able to observe our understanding of LPTs evolve in real time.

"Each new discovery is helping us piece together the bigger picture," Rose says.

"We're only just beginning to understand this new class of cosmic events."

The research has been published in Nature Astronomy.

ScienceAlert stories are written, fact-checked, and edited by humans, never generated by AI. Don't miss a story, subscribe here.

Humans are not yet done cooking. We're continuing to evolve and adjust to the world around us, the records of our adaptations written in our bodies.

We know that some environments can make us unwell. Mountain climbers often experience altitude sickness – the body's reaction to a significant drop in atmospheric pressure, which means less oxygen is taken in with each breath.

And yet, at high altitudes on the Tibetan Plateau, where oxygen levels in the air people breathe are notably low, human communities thrive.

Over more than 10,000 years of settlement in the region, the bodies of those living there have changed.

They've changed in ways that allow the inhabitants to make the most of an atmosphere that, for most humans, would result in insufficient oxygen being delivered to the body's tissues via blood cells, a condition known as hypoxia.

Watch the video below for a summary of the research:

"Adaptation to high-altitude hypoxia is fascinating because the stress is severe, experienced equally by everyone at a given altitude, and quantifiable," anthropologist Cynthia Beall of Case Western Reserve University in the US told ScienceAlert.

"It is a beautiful example of how and why our species has so much biological variation."

Beall has been studying the human response to hypoxic living conditions for years. In research published in October 2024, she and her team revealed some of the specific adaptations in Tibetan communities: traits that improve the blood's ability to deliver oxygen.

To unlock this discovery, the researchers looked into one of the markers of what we call evolutionary fitness: reproductive success.

Women who deliver live babies are those who pass on their traits to the next generation.

The traits that maximize an individual's success in a given environment are most likely to be found in women who are able to survive the stresses of pregnancy and childbirth.

These women are more likely to give birth to more babies.

Those offspring, having inherited survivability traits from their mothers, are also more likely to survive, reproduce, and carry those same traits forward.

That's natural selection at work.

Natural selection can be a bit strange and counterintuitive; in places where malaria is common, for example, the incidence of sickle cell anemia is high, because it involves a gene that protects against malaria.

Beall and her team studied 417 women aged 46 to 86 who had lived their entire lives in Nepal at altitudes above 3,500 meters (11,480 feet).

The researchers recorded the number of live births – ranging from 0 to 14 per woman, with an average of 5.2 – along with physical and health measurements.

Among the things they measured were levels of hemoglobin, the protein in red blood cells responsible for delivering oxygen to tissues.

They also measured how much oxygen was being carried by the hemoglobin.

Interestingly, the women who demonstrated the highest rate of live births had hemoglobin levels that were neither high nor low, but average for the testing group.

But the oxygen saturation of their hemoglobin was high.

The results suggest that the adaptations are able to maximize oxygen delivery to cells and tissues without thickening the blood – an outcome that would increase stress on the heart as it struggles to pump a higher-viscosity fluid more resistant to flow.

"Previously we knew that lower hemoglobin was beneficial; now we understand that an intermediate value has the highest benefit," Beall said.

"We knew that higher oxygen saturation of hemoglobin was beneficial; now we understand that the higher the saturation, the more beneficial. The number of live births quantifies the benefits.

"It was unexpected to find that women can have many live births with low values of some oxygen transport traits if they have favorable values of other oxygen transport traits."

The women with the highest reproductive success rate also had a high rate of blood flow into the lungs, and their hearts had wider-than-average left ventricles, the chamber of the heart responsible for pumping oxygenated blood into the body.

Taken all together, these traits increase the rate of oxygen transport and delivery, enabling the human body to make the most of the low oxygen in the air respired.

It's important to note that cultural factors can play a role, too. Women who start reproducing young and have long marriages seem to have a longer exposure to the possibility of pregnancy, which also increases the number of live births, the researchers found.

Even taking that into account, however, the physical traits played a role. Nepalese women with physiologies most similar to women in unstressed, low-altitude environments tended to have the highest rate of reproductive success.

Related: Humans in The Andes Appear to Have Evolved a Strange Genetic Ability

"This is a case of ongoing natural selection," Beall said.

"Understanding how populations like these adapt gives us a better grasp of the processes of human evolution."

The research was published in the Proceedings of the National Academy of Sciences.

An earlier version of this article was published in October 2024.

ScienceAlert stories are written, fact-checked, and edited by humans, never generated by AI. Don't miss a story, subscribe here.

In 2019, astronomers recorded a distant star doing something unexpected.

For about an hour, its brightness gently flared before settling back down to baseline levels.

Its behavior matched no obvious stellar phenomenon – too long for a stellar flare, too brief for a supernova, and too smooth for most known kinds of stellar variability.

Now, after a careful probe into the event's properties, astronomers say it could be a signal from one of the most elusive objects in the Universe: a tiny primordial black hole weighing only about as much as three of Earth's Moons.

A black hole of that mass would have an event horizon about the same size as the period at the end of this sentence.

A team of astronomers led by Renee Key of Swinburne University of Technology in Australia say that no other explanation fits the event's statistics quite so well, and so they've named the candidate black hole Phoebe.

"Phoebe suggests a population of compact, lunar-mass objects associated with the dark matter distribution of the Milky Way, and potentially opens a new window to the physics of inflation," the team writes in a preprint posted to arXiv.

We tend to think of black holes as really weighty, large objects – with masses starting at at least a few Suns, and ranging all the way up to tens of billions of Suns.

This is because of the way they form, starting with the death of a massive star whose giant core then collapses under gravity, giving birth to one of the densest known objects in the Universe.

Just after the Big Bang, however, conditions may have been just right to create much, much smaller black holes. Quantum fluctuations in space-time could have created overdensities in the expanding Universe that collapsed much as a stellar core can today.

These black holes are known as primordial black holes, and currently, they are only known to exist in the world of theory.

This could be because they are hard to detect. A primordial black hole the mass of Earth would be just 1.8 centimeters (0.7 inches) across.

Even if such a black hole did manage to have an accretion event, the light screaming from the material caught in its gravitational grasp would be barely a pinprick – not detectable from Earth with our current instruments.

But that's not the only way we could detect a primordial black hole.

Even at very tiny diameters, the gravity around these objects would be extreme enough to bend space-time outside the event horizon.

This region of strongly curved space-time can act as a cosmic lens, and any background light passing through it would be magnified, producing a brief, gentle brightening before returning to normal levels – what is known as a microlensing event.

That's exactly the kind of signal the Dark Energy Camera (DECam) recorded in 2019 when it turned its gaze in the direction of the Large Magellanic Cloud, about 163,000 light-years away from Earth.

The event took place on December 18, when DECam ran for five consecutive nights as part of the Asteroid-Mass Primordial black hole Microlensing (AMPM) survey.

For about 60 minutes, the light of a star in the Large Magellanic Cloud grew in brightness when its neighboring light sources did not.

Microlensing events are rare, but not unknown. Previous microlensing events have been attributed to stellar-mass black holes, tiny, dim stars and their attendant worlds, or rogue exoplanets drifting through space untethered from a star.

To find whether Phoebe could be a black hole, the researchers had to first rule out glitches in the instrument, stellar flares, contamination from other stars, and stellar fluctuations.

Then, they had to model different microlensing scenarios: a free-floating exoplanet in the Milky Way; a free-floating exoplanet in the Large Magellanic Cloud; and a primordial black hole in the Milky Way's extended dark matter halo, away from the concentration of matter in the galactic plane.

According to their calculations, the lensing body, Phoebe – whatever it is – is five orders of magnitude more likely to belong to the Milky Way's dark matter halo than to known stellar populations in either galaxy.

The preferred explanation is that Phoebe is a primordial black hole, about three times the mass of the Moon, located around 59,630 light-years away.

That doesn't rule out a rogue exoplanet in the Milky Way's halo. In fact, the rogue exoplanet is still firmly on the table, given that, observationally at least, rogue exoplanets are far more likely to exist and be detected.

But, in the Milky Way's halo, which is only sparsely populated at best, a black hole is far more likely than a rogue exoplanet, which are generally thought to be more populous in regions of space that have a lot of stars.

The discovery lands smack-bang amid another debate.

In February 2026, astronomers in the US and Japan, analyzing data from the Subaru Telescope, identified 12 microlensing candidates toward Andromeda that, they said, could be due to primordial black holes.

Then, a different team from the University of Warsaw, Poland, reanalyzed the same data and uploaded their rebuttal in March, finding that every one of the events could be attributed to normal, known stars.

Related: LIGO May Have Detected The First Primordial Black Hole, Scientists Say

This new discovery is grist for this debate.

Key and her colleagues say their finding supports the original interpretation of the Subaru data that the events are consistent with primordial black holes.

Which means only one thing. We're going to need a more sensitive telescope.

"Our detection motivates the Roman and Vera C. Rubin Observatory microlensing programs to support high cadence, sit-and-stare observations to boost the sensitivity to low-mass microlenses," the team writes in their paper.

We can't wait.

The preprint is available on arXiv.

ScienceAlert stories are written, fact-checked, and edited by humans, never generated by AI. Don't miss a story, subscribe here.

If you've ever tried to overhaul a garden, you know you're bound to find broken bits of pottery and long-forgotten statuary swallowed by vines.

But for one couple, that imitation of archaeological discovery turned into the real thing.

At first glance, the marble slab etched in Latin – including the phrase "spirits of the dead" – might have looked like a mass-produced facsimile designed to lend a garden a little decorative gravitas.

But for anthropologist Daniella Santoro, who lives with her husband Aaron Lopez in a historic home in New Orleans' Carrollton neighborhood, the object – found half-buried in the undergrowth – set off some spidey senses.

For a moment, she feared they might have uncovered an old grave.

"The fact that it was in Latin that really just gave us pause, right?" Santoro told the Associated Press.

"I mean, you see something like that and you say, 'Okay, this is not an ordinary thing.'"

Instead of ignoring the instinct, Santoro reached out to experts.

Among those who examined the inscription were archaeologist Susann Lusnia of Tulane University and anthropologist D. Ryan Gray of the University of New Orleans, who shared the find with other colleagues.

It didn't take long for the researchers to recognize what the couple had found.

The Latin text begins Dis Manibus – "to the spirits of the dead" – a common dedication on Roman funerary tablets.

In Roman funerary practice, Dis Manibus was a standard dedication to the spirits of the departed, often carved at the top of tombstones. Thousands of such inscriptions survive across the former Roman Empire.

Further translation revealed that the stone commemorated a Roman soldier, a Thracian named Sextus Congenius Verus.

Commissioned by his heirs, Atilius Carus and Vettius Longinus, the grave marker records that he died at 42, after 22 years of military service – some 1,900 years before Santoro and Lopez found his grave marker in an overgrown garden, half a world away.

Intriguingly, this was not the first record of the stone. Early in the 20th century, it had been documented as part of the collection of the National Archaeological Museum of Civitavecchia, Italy, a port town where the grave marker once stood in a small cemetery.

The museum was heavily damaged during Allied bombing in 1943 and 1944, and numerous artifacts were lost or displaced. Across Europe, wartime bombing and looting displaced countless cultural artifacts, many of which remain unaccounted for decades later.

The grave marker was among those later listed as missing. Its exact measurements, as recorded by the museum, matched those of the tablet found in Santoro and Lopez's garden.

Exactly how the stone traveled from wartime Italy to suburban Louisiana remained an equally fascinating saga.

According to Erin Scott O'Brien, the Carrollton house's former owner, the tablet had been on display in a cabinet containing other heirlooms in the Gentilly house of her grandfather, Charles Paddock Jr., a soldier stationed in Italy during WWII.

Related: 'Mammoth' Bones Kept in a Museum For 70 Years Turn Out to Be An Entirely Different Animal

Paddock Jr. and his wife died in the 1980s; when O'Brien moved into the home in the early 2000s, her mother gifted her the stone.

"We planted a tree and said this is the start of our new house. Let's put it outside in our garden," O'Brien told Preservation in Print. "I just thought it was a piece of art. I had no idea it was a 2,000-year-old relic."

More than 80 years have passed since the museum that once held the relic was devastated by war, and the principal players in the drama are dead.

It's likely we'll never know the true story of how Paddock came into possession of the stone, but perhaps what really matters is that it's finally returning home – to the land of the empire Sextus Congenius Verus so faithfully served.

The FBI's Art Crime Team is coordinating its repatriation to the National Archaeological Museum of Civitavecchia.

An earlier version of this article was published in February 2026.

ScienceAlert stories are written, fact-checked, and edited by humans, never generated by AI. Don't miss a story, subscribe here.