Subaru Telescope Discovers "Fossil" of the Early Solar System

Figure 1: Artist’s illustration of the distant Solar System object nicknamed "Ammonite."
Credit: AI-generated illustration by Ying-Tung Chen (ASIAA))

Figure 2：The orbit of Ammonite (red line) and the orbits of the other three sednoids (white lines). Ammonite was discovered close to its perihelion, at a distance of 71 astronomical units (71 times the average distance between the Sun and Earth). The yellow point shows its position as of July 2025. Credit: NAOJ

Figure 3: This animation shows the motion of Ammonite over several hours. Based on its brightness at the time of observation, its diameter is estimated to be between 220 and 380 kilometers. Credit: NAOJ/ASIAA

---

The Subaru Telescope has revealed a fourth member of the sednoids, a group of small bodies with peculiar orbits around the outer edge of the Solar System that includes Sedna. The new object, officially designated 2023 KQ14, has been nicknamed "Ammonite" by the research team. Numerical simulations indicate that it has maintained a stable orbit since the early stages of the Solar System's formation. Ammonite is expected to serve as a "fossil" preserving memories of the Solar System's infancy. It may provide clues to the existence of the hypothetical Planet Nine and the origins of the Solar System.

Ammonite was discovered by the survey project "FOSSIL" (Formation of the Outer Solar System: An Icy Legacy), which uses the Subaru Telescope’s wide-field prime-focus camera, Hyper Suprime-Cam (HSC). FOSSIL was launched in 2020 by an international team led primarily by researchers from Japan and Taiwan to explore the icy worlds of the outer Solar System. FOSSIL aims to uncover the history of the Solar System from past to present by observing small bodies that retain traces of planetesimals formed when the Solar System was born. The name "FOSSIL" reflects the project's goal of uncovering the “fossils” of the Solar System.

"In recent years, spacecrafts have been sent to various small bodies in the Solar System for close observation and sample collection. However, these spacecrafts have only explored limited regions of the Solar System. Most of the vast Solar System remains unexplored. Wide-field observations with the Subaru Telescope are steadily pushing back the frontier," says Dr. Fumi Yoshida of the University of Occupational and Environmental Health and the Chiba Institute of Technology, who leads FOSSIL.

Ammonite was discovered by the survey project "FOSSIL" (Formation of the Outer Solar System: An Icy Legacy), which uses the Subaru Telescope’s wide-field prime-focus camera, Hyper Suprime-Cam (HSC). FOSSIL was launched in 2020 by an international team led primarily by researchers from Japan and Taiwan to explore the icy worlds of the outer Solar System. FOSSIL aims to uncover the history of the Solar System from past to present by observing small bodies that retain traces of planetesimals formed when the Solar System was born. The name "FOSSIL" reflects the project's goal of uncovering the “fossils” of the Solar System.

The FOSSIL team also conducted numerical simulations of Ammonite’s orbital evolution using computational resources including the PC Cluster operated by the National Astronomical Observatory of Japan. The results showed that Ammonite has maintained a stable orbit for at least 4.5 billion years. Although its current orbit differs from those of the other sednoids, the simulations indicate that their orbits were remarkably similar around 4.2 billion years ago.

The fact that Ammonite currently follows an orbit different from the other sednoids suggests that the outer Solar System is more diverse and complex than previously thought. It also imposes new constraints on the hypothetical Planet Nine. The numerical simulations conducted in this study suggest that if Planet Nine exists, its orbit should lie even farther out than previously predicted. Furthermore, the existence of Planet Nine would also need to explain why Ammonite’s orbit does not cluster with those of the other sednoids.

Dr. Yukun Huang of the National Astronomical Observatory of Japan who conducted simulations of Ammonite’s orbit comments, "The fact that Ammonite’s current orbit does not align with those of the other three sednoids lowers the likelihood of the Planet Nine hypothesis. It is possible that a planet once existed in the Solar System but was later ejected, causing the unusual orbits we see today."

Regarding the significance of this discovery, Dr. Fumi Yoshida states, "Ammonite 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 Ammonite formed. 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."

Video: This animation shows the orbit of a newly discovered sednoid, 2023 KQ14, in red, along with the orbits of the three previously known sednoids in white. The grid in the background is aligned with the ecliptic plane, with each square representing 100 astronomical units (au). Credit: NAOJ

These results appeared as Ying-Tung Chen et al. "Discovery and Dynamics of a Sedna-like Object with a Perihelion of 66 au" in Nature Astronomy on July 14, 2025.

Source: Subaru Telescope

---

Relevant Links

• ASIAA July 15 2025 Press Release
• NAOJ July 15, 2025 Press Release
• NAOJ Center for Computational Astrophysics July 15, 2025 Press Release
• Planetary Exploration Research Center (Chiba Institute of Technology) July 15, 2025 News

---

About the Subaru Telescope

The Subaru Telescope is a large optical-infrared telescope operated by the National Astronomical Observatory of Japan, National Institutes of Natural Sciences with the support of the MEXT Project to Promote Large Scientific Frontiers. We are honored and grateful for the opportunity of observing the Universe from Maunakea, which has cultural, historical, and natural significance in Hawai`i.

---

Crustal Clues to Earth’s Formation

An illustration of rocky material bombarding the young Earth
Credit: NASA Goddard

Earth’s crust contains chemical elements that we’d expect to find in its core, not near its surface. What can detailed simulations of planet formation tell us about the likely origins of these elements?

A plot of the abundances of individual chemical elements in Earth’s crust. The siderophile elements, outlined in yellow, are rare in Earth’s crust, though not as rare as expected. Credit: Gordon B. Haxel, Sara Boore, and Susan Mayfield from USGS

A Crash Course in Earth History
 

Early in the solar system’s history, rocky planetesimals collided to form larger bodies and eventually planets. As early Earth accreted material through collisions, siderophile (“iron-loving”) elements like gold and platinum dissolved into the young planet’s iron-rich core. However, present-day Earth has an unexpectedly large amount of these elements in its crust, indicating that they were added to the planet late in its formation.

The number, size, origin, and composition of the objects that delivered this final sprinkling of siderophile elements is still uncertain, though. Now, astronomers have used simulations to make sense of the elements found in Earth’s crust and reconstruct our home planet’s formation history.

Location, masses, and origins of planetesimals in the Grand Tack simulation (left) and the calm accretion simulation (right). The top row shows the beginning of the simulation and the bottom row shows the end. In the calm accretion scenario, the planetesimals tend to contain material sourced from their location (indicated by the symbol color). In the Grand Tack model, the planetesimals tend to become “bluer” because of material moved inward by Jupiter. Click to enlarge. Credit: Adapted from Carter & Stewart 2022

Plentiful Planetesimals

Philip Carter (University of Bristol, UK, and University of California, Davis) and Sarah Stewart (University of California, Davis) set out to understand if Earth’s unusual crustal composition could be due to collisions with planetesimals late in the planet’s formation history. To do so, the team used numerical models to track the composition of tens of thousands of simulated planetesimals as they migrated and collided over a period of 21 million years. The authors explored two scenarios for the dynamics of the inner solar system: the Grand Tack model, in which a simulated Jupiter barrels into the inner solar system before retreating to its current location, and the calm accretion model, in which there is no disturbance from a giant planet.

In the calm accretion model, planetesimals tended to collect material from very close to their birthplace. Since the composition of the planet-forming disk changes as a function of distance from the Sun, this means that planetesimals forming at different distances from the Sun had different compositions.

In the Grand Tack model, on the other hand, Jupiter’s migration mixes the material in the inner solar system, leading to the formation of planetesimals containing a blend of material from throughout the inner solar system. In this scenario, planetesimals at a range of distances from the Sun had similar compositions.

The Grand Tack model concentrates mass in a region located 0.8–1.3 au from the Sun. The Jupiter-induced mixing in this region results in a substantial fraction of planetesimals with similar composition to the planetary embryos that are present within 0.2 au. Credit: Adapted from Carter & Stewart 2022

Ample Earth-Like Material

If Jupiter’s migration shook up the inner solar system, it may have created plenty of planetesimals similar in composition to Earth. If those planetesimals collided with Earth late in its formation, they could distribute the siderophile elements in their cores over Earth’s surface.

This scenario could also explain why the Moon has the same chemical signature as Earth; if the Mars-sized protoplanet hypothesized to have collided with Earth to form the Moon contained elements in similar ratios to Earth, that would naturally explain the Moon’s composition.

Plenty of questions remain, but the new simulations make a compelling case that collisions between early Earth and material similar in composition could explain many aspects of present-day Earth. For more details and future prospects, be sure to read the full article cited below!

Citation

“Did Earth Eat Its Leftovers? Impact Ejecta as a Component of the Late Veneer,” Philip J. Carter and Sarah T. Stewart 2022 Planet. Sci. J. 3 83. doi:10.3847/PSJ/ac6095

 

By Kerry Hensley

Source:American Astronomical Society - AAS Nova

---

Three’s a crowd

(130) Elektra
Credit: ESO/Berdeu et al., Yang et al.

Between Mars and Jupiter lie some of the relics of the early Solar System: the main asteroid belt. This belt is full of unusual asteroids whose origins reveal the building blocks of the early terrestrial planets. Of these, one of the more intriguing is Elektra, imaged here using the instrument SPHERE, installed on ESO’s Very Large Telescope at Paranal, Chile. 

Previously, Elektra was known to have not one but two moons orbiting it, shown by the orange and green orbits respectively. But now a team of astronomers, led by Anthony Berdeu, from the National Astronomical Research Institute of Thailand, have found a new satellite orbiting the asteroid — shown with the blue orbit. This discovery makes Elektra the first ever quadruple asteroid system.

This new, third moonlet of Elektra, provisionally named S/2014 (130) 2, lies closer to its parent asteroid than the other moons, at an average distance just under 350 km, and is 15000 times fainter than Elektra. The team used public data from the ESO science archive and a new processing technique to reveal this small moon. The discovery will help astronomers understand how these satellites form and, in turn, provides crucial information about planetary formation and evolution of our own solar system.

SPHERE, the Spectro-Polarimetric High-contrast Exoplanet REsearch instrument, is a powerful planet-finding instrument. It uses an extreme adaptive optics system which allows for real time corrections of turbulence in the Earth’s atmosphere which causes stars to twinkle. It was only with SPHERE’s sensitivity and spatial resolution, coupled with cutting-edge data processing techniques, that the team was able to spot Elektra’s newest satellite.

Link

• Video showing the asteroid and its moons in motion
• Three's a crowd (non-annotated)

Source: ESO/potw

---

Extinct atom reveals the long-kept secrets of the solar system

The unstable atom 92Nb, which has long since disappeared, provides information about the beginnings of our solar system.
Illustration: Makiko K. Haba

Using the extinct niobium-​92 atom, ETH researchers have been able to date events in the early solar system with greater precision than before. The study concludes that supernova explosions must have taken place in the birth environment of our sun.

If an atom of a chemical element has a surplus of protons or neutrons, it becomes unstable. It will shed these additional particles as gamma radiation until it becomes stable again. One such unstable isotope is niobium-​92 (⁹²Nb), which experts also refer to as a radionuclide. Its half-​life of 37 million years is relatively brief, so it went extinct shortly after the formation of the solar system. Today, only its stable daughter isotope, zirconium-​92 (⁹²Zr), bears testimony to the existence of ⁹²Nb.

Yet scientists have continued to make use of the extinct radionuclide in the form of the ⁹²Nb-⁹²Zr chronometer, with which they can date events that took place in the early solar system some 4.57 billion years ago.

Use of the ⁹²Nb-⁹²Zr chronometer has hitherto been limited by a lack of precise information regarding the amount of ⁹²Nb that was present at the birth of the solar system. This compromises its use for dating and determining the production of these radionuclides in stellar environments.

Meteorites hold the key to the distant past

Now a research team from ETH Zurich and the Tokyo Institute of Technology (Tokyo Tech) has greatly improved this chronometer. The researchers achieved this improvement by means of a clever trick: they recovered rare zircon and rutile minerals from meteorites that were fragments of the protoplanet Vesta. These minerals are considered to be the most suitable for determing ⁹²Nb, because they give precise evidence of how common 92Nb was at the time of the meteorite's formation. Then, with the uranium-​lead dating technique (uranium atoms that decay into lead), the team calculated how abundant ⁹²Nb was at the time the solar system’s formation. By combining the two methods, the researchers succeeded in considerably improving the precision of the ⁹²Nb-⁹²Zr chronometer.

“This improved chronometer is thus a powerful tool for providing precise ages for the formation and development of asteroids and planets – events that happened in the first tens of millions of years after the formation of the solar system,” says Maria Schönbächler, Professor at the Institute of Geochemistry and Petrology at ETH Zurich, who led the study.

Supernova released niobium-92

Now that the researchers know more precisely how abundant ⁹²Nb was at the very beginnings of our solar system, they can determine more accurately where these atoms were formed and where the material that makes up our sun and the planets originated.

The research team’s new model suggests that the inner solar system, with the terrestrial planets Earth and Mars, is largely influenced by material ejected by Type Ia supernovae in our Milky Way galaxy. In such stellar explosions, two orbiting stars interact with each other before exploding and releasing stellar material. In contrast, the outer solar system was fed primarily by a core-​collapse supernova – probably in the stellar nursery where our sun was born –, in which a massive star collapsed in on itself and exploded violently.

Reference  Releated Articles

Haba MK, Lai Y-J, Wotzlaw J-F, Yamaguchi A, Lugaro M, Schönbächler M. Precise initial abundance of Niobium-​92 in the Solar System and implications for p-​process nucleosynthesis. PNAS February 23, 2021 118 (8) e2017750118. DOI: 10.1073/pnas.2017750118

Releated Articles

• Stardust from red giants (ETH-​News 09.12.2019)
• Stony ambassadors from the asteroid Vesta (ETH-​News 12.06.2019)

By:  Peter Rüegg

Source:  ETH Zurich /News

---

Simulating nature’s cosmic laboratory, one helium droplet at a time

Schematic representation of the new method: Two reactants R1 and R2 are added to a helium droplet. The energy released in the resulting reaction decreases the droplet’s size. The decrease in size can be measured, and allows researchers to deduct the reaction energy. Image: Krasnokutskiy / MPIA

Two astronomers from the Max Planck Institute for Astronomy and from the University of Jena have found an elegant new method to measure the energy of simple chemical reactions, under similar conditions as those encountered by atoms and molecules in the early solar system. Their method promises accurate measurements of reaction energies that can be used to understand chemical reactions under space conditions – in cluding those reactions that were responsible of creating organic chemicals as the raw material for the development of life.

In order for life to form, nature needed plenty raw materials in the shape of complex organic molecules. Some of those molecules are likely to have formed long before, in space, during the birth of the Solar System. Systematic studies of the necessary chemical reactions, which take place on the craggy and convoluted surfaces of dust grains, were and are hampered by a lack of data. Which elementary reactions, involving which individual reactants are possible? What temperature is required for a reaction to take place? Which molecules are produced in those reactions? Now, Thomas Henning, director at the Max Planck Institute for Astronomy (MPIA), and Sergiy Krasnokutskiy of the MPIA’s Laboratory Astrophysics Group at the University of Jena have developed an elegant method to study such elementary surface reactions – using minute liquid helium droplets.

In the early solar system, long before the formation of Earth, complex chemical reaction took place, creating substantial amounts of organic molecules. The cosmic laboratory for these works of chemical synthesis was provided by grains of dust – clusters of mostly silicates and carbon, covered with a mantle of ice, with complicated and delicate tendrils and ramifications, and on this basis with one crucial property: A comparatively large surface on which chemical reactions could take place. In the millions of years that follows, many of those dust grains would cluster together for form ever larger structures, until finally, solid planets emerged, orbiting the young Sun.

Creating the raw ingredients for life

While all of the organic compounds synthesized on the grain surfaces would be destroyed by the unavoidable heat during planet formation, some of the molecules remained in waiting, encapsulated in, or clinging to the surface of, smallish grains or lumps of rock, as well as in the icy bodies of the comets. By one account of the history of life, once Earth’s surface had cooled sufficiently for liquid water to form, it was these grains and rocks, hitting Earth’s surface in the shape of meteorites, some of them landing in warm, small, ponds, that provided the chemical basis for life to form on our home planet.

In order to understand the early natural chemical experiments in our universe, we need to know the properties of the various reactions. For instance, do certain reactions need a specific activation energy to happen? What is the eventual product of a given reaction? Those parameters determine which reactions can happen under what conditions in the early Solar system, and they are key for any realistic reconstruction of early Solar system chemistry.

Scarce data about low-temperature surface reactions

Yet precise data on these reactions is surprisingly scarce. Instead, a substantial part of chemical research is dedicated to the study of such reactions in the gaseous phase, with the atoms and molecules floating freely, colliding, and forming compounds. But the crucial chemical reactions in space needed to build up larger organic molecules take place under markedly different conditions – on the surfaces of dust grains. This changes even the basic physics of the situation: When a new molecule is formed, the energy of the chemical bond formation is stored in the newly created molecule. If this energy is not passed on to the environment, the new molecule will quickly be destroyed. This prevents the formation of many species of in the gas phase. On a surface, or in a medium, where energy can readily be absorbed by the additional matter present, the conditions for certain types of reactions building complex molecules, step by step, are much more favorable.

Henning and Krasnokutskiy developed an elegant method for measuring the energetics of such reactions. Their mock-ups of cosmic laboratories are miniature helium droplets, a few nanometers in size, drifting in a high vacuum. The reactants – that is, the atoms or molecules meant to take part in the reaction – are brought into the vacuum chamber as gases, but in such minute amounts that helium droplets are overwhelmingly likely to pick up either a single molecule of each required species or none, but not more. The helium droplets act as a medium that, similar to the surface of a dust grain, can absorb reaction energy, allowing reactions to happen under similar conditions to those in the early Solar system. This reproduces a key feature of the relevant surface chemistry (although other properties, such as catalytic properties of a specific dust surface, are not modelled).

Nanodrops as measuring devices

Furthermore, the two astronomers used the helium nanodrops as energy measuring devices (calorimeters). As reaction energy is released into the drop, some of the Helium atoms will evaporate in a predictable fashion. The remaining drop is now smaller than before – a difference in size that can be measured using two alternative methods: an electron beam (a larger drop is easier to hit than a smaller one!) or a precise measurement of the pressure in the vacuum chamber created by Helium droplets hitting the wall, where larger droplets produce greater pressure. By calibrating their method using reactions that had been studied in detail beforehand, and whose properties are well-known, the two astronomers were able to increase the method’s accuracy considerably. All in all, the new method provides an elegant new way of investigating the formation pathway of complex organic molecules in space. This should enable researchers to be more specific about the raw materials nature had to work with in the run-up of the emergence of life on Earth. But there is more:

The first measurements using the new technique confirm a trend that had already been visible in other recent experiments: On surfaces, at low temperatures, carbon atoms are surprisingly reactive. The researchers found a surprisingly high number – almost a dozen – of reactions involving carbon atoms which are barrierless, that is, which do not require extra energy input to proceed, and hence can occur at very low temperatures. Evidently, the condensation of atomic gas at low temperatures is bound to lead to the formation of a large variety of organic molecules. But that large possible variety also means that molecules of each specific species will be very rare.

This, in turn, suggests that astronomers might be drastically underestimating the amount of organic molecules in outer space. When it comes to estimating abundances, astronomical observations examine the trace signatures (spectral lines) of each molecular species separately. If there are many different species of organic molecules out there, each separate species can “fly under the radar.” Its molecules might be present only in amounts too minute for astronomers to detect, and in addition, even the tell-tale signatures of the molecules (more generally those of specific functional groups common to different types of molecules) could be slightly altered, making the molecule evade detection. But added up, it is possible that all these separate species of molecule together could make up a substantial amount of matter in outer space – a hidden outer-space world of organic chemistry.

Background information

The results presented here have been published as Henning, Th. & S. A. Krasnokutski 2019, “Experimental Characterization of the Energetics of Low-temperature Surface Reactions” in the journal Nature Astronomy.

Journal article

---

Science contact

Sergiy Krasnokutskiy
Email: sergiy.krasnokutskiy@uni-jena.de

PR contact

Markus Pössel
Public Information Officer
Phone:+49 6221 528-261
Email: pr@mpia.de

Source: Max Planck Institute for Astronomy/Science Releases

---