Category: 7. Science

Despite the powerful telescopes that modern astronomers have to work with, the distant reaches of the Solar System are still mysterious. Not much sunlight pierces these regions, and there are strong hints that undiscovered objects lurk there. The objects that astronomers have discovered in these dim reaches are primordial, and their orbits suggest the presence of more undiscovered objects. Piecing it all together is a challenge.

While some objects announce themselves with fiery explosions or streaks of light across the sky, distant Solar System objects don’t attract much attention. They reveal themselves in tiny hints; a nearly imperceptible tug on another object, a nearly-invisible and short-lived glimmer of light. Yet these objects have something important to tell us about how our Solar System formed and evolved.

Astronomers have detected hints of a ninth planet in the Solar System’s distant reaches. This hypothetical and elusive Planet Nine is held up to explain the puzzling orbital groupings of a family of distant objects called Trans-Neptunian Objects (TNO).

Astronomers working with Japan’s Subaru Telescope in Hawaii found evidence of a new distant object in the Solar System. It’s a Trans-Neptunian Object, meaning it orbits the Sun at a greater average distance than Neptune, the outermost planet. But it’s also a member of an important and puzzling sub-class of objects: Sednoids. It’s name is 2023 KQ14, but its nickname is Ammonite, after the fossilized cephalopod.

Sednoids follow more extreme orbits than TNOs. Their orbits are extremely elongated, with high eccentricity, distant perihelia, and large semi-major axes. They’re named after the dwarf planet Sedna, and the new discovery is only the fourth Sednoid ever detected.

A new paper in Nature Astronomy presented the discovery. It’s titled “Discovery and dynamics of a Sedna-like object with a perihelion of 66 au.” The lead author is Ying-Tung Chen from the Academia Sinica Institute of Astronomy and Astrophysics in Taipei, Taiwan.

“Understanding the orbital evolution and physical properties of these unique, distant objects is crucial for comprehending the full history of the Solar System.” – Dr. Fumi Yoshida, co-author.

Ammonite was first detected with the Subaru Telescope during observation efforts in March, May, and August 2023. Those observations alone weren’t sufficient to confirm the dim object’s existence, and follow-up observations in July 2024 with the Canada-France-Hawaii Telescope, as well as a search through archived data from other observatories, provided confirmation. Overall, the researchers tracked Ammonite’s orbit for 19 years.

Ammonite was found as part of the FOSSIL (Formation of the Outer Solar System: An Icy Legacy) observing program. It uses the Subaru Telescope’s powerful HyperSuprimeCam to measure the populations and sub-populations of the objects that populate the outer Solar System. The FOSSIL team used computer numerical simulations to determine that Ammonite has followed a stable orbit for at least 4.5 billion years, dating all the way back to the Solar System’s earliest times. Ammonite’s orbit is currently different from the other Sednoids, but the simulations show that there orbits were all similar about 4.2 billion years ago.

There’s an odd gap in distant Solar System objects when it comes to their perihelion distances and Ammonite sits in that gap. “The orbit of Ammonite does not align with those of the other Sedna-like objects and fills the previously unexplained ‘q-gap’ in the observed distribution of distant Solar System objects,” the authors explain in their paper.

This figure is divided into two panels divided by a vertical black line, and shows the orbital data for outer Solar System objects. The left side shows the semi-major axis versus perihelion distribution, with the red vertical dashed line representing the approximate region where galactic tides and passing stars can perturb the orbits of TNOs. The horizontal black lines show the upper boundary of chaotic diffusion and gravitational scattering by Neptune. The named objects all have large perihelia, and it clearly shows hos Ammonite is different from the others. It’s in the region that currently lacks any other detections. The right side shows how Ammonite falls outside the proposed clustering of objects with large perihelia. Image Credit: Chen et al. 2025. NatAstr. https://doi.org/10.1038/s41550-025-02595-7

Dr. Yukun Huang of the NAOJ is a co-author of the paper who conducted simulations of Ammonite’s orbit. “The fact that 2023 KQ14’s current orbit does not align with those of the other three sednoids lowers the likelihood of the Planet Nine hypothesis,” Huang said in a press release. “It is possible that a planet once existed in the Solar System but was later ejected, causing the unusual orbits we see today.”

Neptune is the only known massive object near the outer Solar System that could have shaped the orbits of the TNOs and Sednoids. But according to study co-author Dr. Fumi Yoshida, Ammonite is beyond its reach.

“2023 KQ14 was found in a region far away where Neptune’s gravity has little influence. The presence of objects with elongated orbits and large perihelion distances in this area implies that something extraordinary occurred during the ancient era when 2023 KQ14 formed,” Yoshida said. “Understanding the orbital evolution and physical properties of these unique, distant objects is crucial for comprehending the full history of the Solar System. At present, the Subaru Telescope is among the few telescopes on Earth capable of making such discoveries. I would be happy if the FOSSIL team could make many more discoveries like this one and help draw a complete picture of the history of the Solar System.”

Ammonite’s orbit is now different from the other Sednoids, and that fact needs an explanation. It’s evidence that there’s more complexity and diversity among distant Solar System objects. Astronomers have long wondered if our Solar System hosts a ‘Planet Nine’ that has shepherded the orbits of these distant objects. If there is, then Ammonite’s discovery places more constraints on its orbit, and where it may be hiding. It effectively reduces the number of hiding spots for this hypothetical planet.

An artist’s illustration of the mysterious, elusive, hypothesized Planet Nine. Image Credit: NASA

“Sedna-like objects with large semi-major axes (a > 200 au) and large perihelia (q > 60 au) appear to evolve in stable orbits that have remained largely unchanged and not altered by the gravity of Neptune since the formation of the Solar System,” the researchers explain in their paper. “No viable transfer mechanisms to raise their perihelia exist with the current configuration of planets. Their stability suggests that an external gravitational influence beyond those of the currently known Solar System planets is required to form their orbits.”

This figure shows the orbits of the four Sednoids, with Neptune’s orbit around the Sun shown for comparison. “Ammonite’s longitude of perihelion is in the opposite direction of the other Sedna-like objects,” the authors explain. “Its high perihelion suggests the potential for long-term orbital stability,” and it’s valuable for testing the hypothesized clustering of Sednoids and the hypothetical Planet Nine. Image Credit: Chen et al. 2025. NatAstr. https://doi.org/10.1038/s41550-025-02595-7

Astronomers have proposed many sources for this external gravitational influence, including interactions with a rogue planet or star, ancient stellar interactions from when the Sun was still in its natal cluster, and the capture of objects from other lower-mass stars in the Solar System’s early times. But the explanation that gets the most attention is interactions with a hypothetical planet, Planet Nine.

While this study neither confirms nor disputes the existence of Planet Nine, it does place further constraints on its orbit. In fact, each time another Sednoid is discovered, it constrains Planet Nine. Astronomers now know of four of them, but they don’t know how many may still be hiding out there, potentially shepherded by the elusive, hypothetical, Planet Nine.

If Planet Nine exists, it has a huge area to hide in. Some astronomers who have studied its potential existence think it could be the fifth largest planet in the Solar System. It would be so far away that it would be extremely dim. However, we may be on the cusp of detecting it, if it exists.

The Vera Rubin Observatory recently saw first light and will begin its decade-long Legacy Survey of Space and Time (LSST). The LSST will find transient events and objects in the Solar System like no other telescope before it. It’s purpose-built to find hard to detect objects, and not even an elusive object like Planet Nine may be able to hide from it.

Earth’s continents may look fixed on a globe, but they’ve been drifting, splitting and reforming over billions of years – and they still are. Our new study reveals fresh evidence of rhythmic pulses of molten rock rising beneath east Africa, reshaping our understanding of how continents break apart.

Our findings could help scientists understand more about volcanic activity and earthquakes.

There are around 1,300 active volcanoes on the Earth’s surface . Active volcanoes are those thought to have had an eruption over the last 12,000 years or so. Of these volcanoes, over 90 lie on the East African Rift Valley – the seam along which Africa is splitting apart. This weak seam of crust may even allow a new ocean to form over the next few million years.

Although ocean formation is happening around the world, and has been for several billion years, there are few places on Earth where you can study different stages of continental breakup at the same time. This is because they normally become submerged under water as the Earth’s crust thins, and seawater eventually inundates the rift valley.

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The Rift Valley is different. There is, at its northern end (in Ethiopia) a place called Afar, which sits at the meeting point of three rifts . These are called the Red Sea Rift, the Gulf of Aden Rift, and the Main Ethiopian Rift (see the map below).

The Red Sea Rift has been spreading for the last 23 million years , and the Main Ethiopian Rift for the last 11 million years . There are active volcanoes across all three of these rifts. In Afar, all three rifts are at least partly exposed, with the Red Sea Rift and Main Ethiopian Rift having the most exposure.

Volcanic rocks that erupt when Earth’s tectonic plates spread apart provide a window into the inner Earth that wouldn’t otherwise be accessible. Each lava flow and volcano has its own story that is recorded in the rock and we can learn about that through geochemistry – the concentrations of the elements that make up the rock – and mineralogy – the minerals within the rock.

Analysing these things can tell us about the depth at which the melting rock formed and roughly where in the Earth’s mantle it formed. In our new study, we analysed over 130 new lava samples, obtained from the Afar rock repository at the University of Pisa and our own fieldwork.

We used these samples to investigate the characteristics of the mantle beneath this rifting, when tectonic plates are moving apart from each other. These samples are from Holocene eruptions (rocks younger than 11.7 thousand years old) from across Afar and the East African Rift.

Since the 1970s, scientists have believed that there is a mantle plume beneath the Afar region. Mantle plumes are a portion of abnormally hot mantle (around 1,450°C) or unusual composition of the mantle (or both) below the Earth’s surface. Scientists think it pushed some of the mantle to the Earth’s surface. Our study not only confirms the presence of a mantle plume in this region, but also gives scientists details about its characteristics.

We discovered that the mantle plume beneath the region rises beneath the tectonic plates in pulses, and the pulses have slightly different chemical compositions.

There are mantle plumes around the world. They can be identified in the geological record as far back as several billion years . Each of the plumes has different characteristics – with their own unique chemical composition and shape.

One mantle plume still active today is the one lying below the Hawaiian islands. These islands are part of the Hawaiian Emperor chain, formed over the last 80 million years or so , and are still forming today. The islands originate from the Pacific tectonic plate slowly moving across the top of a mantle plume, making lava bubble up, erupt and eventually solidify as rock.

This plume melts the Earth’s mantle and forms magma, which over long periods results in the formation of an island chain or breaks up continents. It can also form volcanoes along a rift in the Earth’s crust, as we see in east Africa. The Hawaiian plume signature comes from two chemical compositions rising up through the mantle together like two vertical strands.

While scientists have long thought there probably is a plume underneath Afar, what it looks like is debated .

In our study, we created several scenarios of what the plume looks like and then used mathematical modelling to see which plume scenario best fit the sample data. Using this data-driven approach, we show that the most likely scenario is a singular plume that pulses with different chemical compositions.

The three rifts in Afar are spreading at different rates. The Red Sea Rift and Gulf of Aden Rift are moving faster at about 15mm per year (that’s half the rate your fingernails grow at) compared to the Main Ethiopian Rift moving at about 5mm per year . We deduced that the pulses are flowing at different speeds along the stretched and thinner undersides of the tectonic plates.

All this shows us that the motion of tectonic plates can help focus volcanic activity to where the plate is thinner.

This finding has important implications for how we interpret volcanic and earthquake activity. It may indicate that volcanism could be more likely to occur in the faster spreading and thinner portions of the rift, as the flow beneath replenishes the magma more frequently.

However, the eruptions here may be less explosive than the slower spreading rifts. This fits observations that explosive eruptions occur more frequently in the Main Ethiopian Rift (which sits on a thicker part of the plate and where the volcanoes are more mature), compared to the Red Sea Rift.

Our understanding of the link between continental rifting and mantle plumes is still in its infancy but research is already providing insights into how tectonic plates affect mantle plumes and how this might be recorded in the future seafloors of Earth.

Emma Watts works for Swansea University. She receives funding from Natural Environment Research Council and the UK Research Council.

Derek Keir works for the University of Southampton. He receives funding from the Natural Environment Research Council.

Thomas Gernon works for the University of Southampton. He receives funding from the WoodNext Foundation, a donor-advised fund program, and from the Natural Environment Research Council.

/Courtesy of The Conversation. This material from the originating organization/author(s) might be of the point-in-time nature, and edited for clarity, style and length. Mirage.News does not take institutional positions or sides, and all views, positions, and conclusions expressed herein are solely those of the author(s).

Geologists have stumbled on what they call gigantic fortresses lying almost 1,800 miles below our feet in Earth’s mantle.

New seismic evidence shows how these subterranean bulwarks are older and tougher than the cooler debris of dead ocean plates that surround them, turning a long‑running mystery into a concrete data story.

Each fortress spans an area comparable to a continent beneath Africa and the Pacific, and registers hotter than its frigid surroundings.

Utrecht University‘s seismologist Arwen Deuss, working with colleagues across Europe, Australia, and the United States, led the crew that pieced together the picture.

Fortresses in Earth’s mantle

The scientific shorthand for the fortresses is large low seismic velocity provinces or LLSVPs, continent‑scale masses perched at the core‑mantle boundary about 1,800 to 1,900 miles down.

They dampen shear waves and slow them, marking them out as zones of hot, sluggish rock that differs sharply from the stiff material around them.

Seismic tomography first lit them up in global maps during the 1990s. Two hulking blobs emerged, one under Africa and one under the central Pacific, each more than 3,000 miles across.

Later surveys confirmed that the African LLSVP towers roughly 600 miles high while its Pacific twin rises even farther.

Yet whether they were temporary stains or ancient fixtures remained unsettled, in part because most models assumed vigorous, homogenizing flow in the lower mantle.

Taken together, the two provinces occupy about eight percent of the mantle’s volume, a reminder that Earth’s interior is far from uniform.

Listening to the planet’s bell

Seismologists treat the Earth like a giant bell that rings when a great quake strikes. The catastrophic 1994 Bolivia event provided tones that hummed for hours, carrying clues from the deepest layers and offering clean, low‑noise data.

“Large earthquakes make the whole Earth ring like a bell with different tones,” said Deuss after reviewing decades of records.

Her team tuned in not only to the pitch shifts but also to how loudly each mode persisted, a seldom‑used metric called quality factor.

That loudness, known as damping, revealed something odd. Vibrations grew quiet in the cold slab graveyard but stayed loud inside the hot fortresses, implying low internal friction and unexpectedly efficient energy transmission.

Against expectation, the LLSVPs sapped little energy from the waves. The finding overturned the simple view that heat alone controls attenuation, forcing scientists to search for another variable.

Texture tells a deeper story

The key lies in grain boundaries, the microscopic seams between crystals in mantle minerals. Fewer seams mean fewer places for energy to bleed away, a principle familiar to anyone who has tried to push water through a coarse versus fine filter.

Subducted plates recrystallize into tiny grains as they plunge, multiplying boundaries and soaking up seismic energy. They show up as the quietest patches in the global map, matching the high‑damping ring around the Pacific.

Inside the fortresses, grains have had eons to grow fat. Large crystals line up like chunky bricks, stiffening the rock and letting waves glide through with little loss, a behavior confirmed in high‑pressure laboratory rigs.

Laboratory tests on olivine confirm the trend, showing that doubling grain size can nearly halve seismic attenuation at mantle temperatures.

That experimental curve fits the numbers seen in the new global model, strengthening the grain‑size explanation.

Restless mantle and giant fortresses

Modeling suggests the grain growth needed to reach that size takes at least 500 million years, perhaps far longer.

The fortresses, therefore, predate many supercontinents that have since broken apart, including Pangea and its earlier cousins.

Such rigidity helps them ignore the slow churn of mantle convection. They stand their ground while cooler slabs crawl and sink around them, like boulders lodged in a riverbed of flowing rock.

“There is less flow in Earth’s mantle than is commonly thought,” Deuss explained, noting that the presence of these immovable masses forces scientists to rethink convection cycles. The textbook picture of a well‑stirred mantle no longer fits.

A layered mantle, part conveyor and part castle, now seems more likely. That hybrid view changes every surface process driven from below, from the drift of continents to the cycling of carbon.

Why the finding matters at the surface

The hot edges of the fortresses appear to be launchpads for mantle plumes that punch up to volcano chains such as Hawaii. Their buoyant rise fuels not only island arcs but also the massive basalt floods seen in Earth’s deep past.

Large igneous provinces linked to mass extinctions tend to cluster above these plume zones. Knowing that the plumes come from fortress margins ties surface cataclysms to deep‑mantle architecture.

Mountain belts form where plates collide, but the deep heat flow that drives those collisions may trace back to these hot roots. In that sense, the fortresses could set the tempo of orogeny and rifting alike.

Over geologic time, their stability may even shape the drift path of continents, steering plates around the mantle’s slow‑moving keystones. That possibility will feed new computer models that link deep convection to plate motions.

What scientists will chase next

Researchers plan denser global arrays and machine‑learning tools to catch fainter normal modes. Each new quake becomes another flashlight aimed into the depths, refining the 3‑D map with every event.

Geochemists will compare volcanic rocks to lab‑made analogs, hunting chemical fingerprints of the fortresses.

A match would close the loop between seismic images and real material, settling the debate over whether the fortresses differ in composition as well as temperature.

Mineral physicists also want to recreate fortress conditions in diamond‑anvil presses, squeezing and heating samples to map how grain growth unfolds through deep time. The work could reveal why some minerals coarsen while others stay fine and brittle.

Meanwhile, geoneutrino observatories may soon detect radioactive decay signatures that differ inside and outside the fortresses.

Any contrast would add a new dimension to the planet‑sized puzzle, linking deep geology to particle physics.

The study is published in Nature.

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