‘Ammonite’: A Mysterious Deep Space Fossil That Could Rewrite Solar System History
How did your country report this? Share your view in the comments.
Diverging Reports Breakdown
“Something Extraordinary Occurred”: A New 380-Kilometer World Has Been Found In Our Solar System
The Subaru telescope located at the Mauna Kea Observatory on Hawai’i has found a new world within our Solar System, dubbed “Ammonite” by the team who found it. The planetoid was the first of the “sednoids” to be discovered; trans-Neptunian objects with highly-eccentric orbits. Their orbits are actually pretty unusual, and there are quite a few hypotheses about how they ended up where they are, ranging from galactic tides to the influence of an (as yet hypothetical) Planet 9. Looking at the other sednoids, the team found that Ammonite’s orbit was remarkably similar, until around 4.2 billion years ago, possibly when an unknown “clustering event” influenced their trajectories, 300 million years after the Solar System was formed. The object is between 220 and 380 kilometers (137 and 236 miles) in diameter. Its perihelion – its closest approach to the Sun – is between 50 and 75 astronomical units (AU), with one AU being the distance between the Earth and the Sun.
In 2003, NASA-funded researchers spotted what was then the most distant object discovered in our Solar System. The dwarf planet, named Sedna after the Inuit goddess of the sea, was found over 12.9 billion kilometers (8 billion miles) from Earth, potentially making it an inner object of the hypothetical “Oort cloud” surrounding our Solar System.
“Sedna is distinguished among other objects mentioned above by its highly elongated orbit and a much greater aphelion radius,” a 2021 paper on the topic explains, adding that the surface composition also shows similarities with Kuiper Belt objects.
“The discoverers have supposed that Sedna was created in the Solar System at the early stage of its evolution, and its orbit was changed because of dynamic effects that followed the Sun’s formation within a dense stellar cluster. According to other versions, Sedna’s orbit was changed by a stellar encounter (e.g., the passing Scholz’s star about 70 thousand years ago at a distance of 52 thousand au from the Sun), or Sedna was captured from a low-mass star or a brown dwarf in interstellar space.”
The planetoid was the first of the “sednoids” to be discovered; trans-Neptunian objects with highly-eccentric orbits. Their orbits are actually pretty unusual, and there are quite a few hypotheses about how they ended up where they are, ranging from galactic tides to the influence of an (as yet hypothetical) Planet 9.
Thanks to the new discovery, we may be a little closer to an answer.
“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,” Dr Fumi Yoshida, leader of the Formation of the Outer Solar System: An Icy Legacy (FOSSIL) project, said in a statement. “Most of the vast Solar System remains unexplored. Wide-field observations with the Subaru Telescope are steadily pushing back the frontier.”
Ammonite, captured over several hours. Image credit: NAOJ, ASIAA
In March, May, and August 2023 the telescope spotted a potential object on the outskirts of our Solar System. Follow-up observations in July 2024 using the Canada-France-Hawaii Telescope confirmed the object – officially named 2023 KQ14 – and its orbit, confirming it as the fourth Sednoid discovered. Further searches of archives showed that the object had been spotted in 2021 and 2014, as well as by the Kitt Peak National Observatory in 2005, allowing the team to narrow down the accuracy of Ammonite’s orbit.
Observations of Ammonite suggest it is between 220 and 380 kilometers (137 and 236 miles) in diameter. Modeling the sednoid’s orbit, the team found its perihelion – its closest approach to the Sun – is between 50 and 75 astronomical units (AU), with one AU being the distance between the Earth and the Sun. Its aphelion – the furthest point from the Sun – it is around 252 AU out from the center.
Simulating the orbit of Ammonite into the past, the team found that it has been stable for at least 4.5 billion years. Looking at the other sednoids, the team found that Ammonite’s orbit was remarkably similar, until around 4.2 billion years ago, possibly when an unknown “clustering event” influenced their trajectories, 300 million years after the Solar System was formed.
“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,” Yoshida added.
“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.”
What caused this clustering of the objects remains an open question, with the possibility of a passing star or an ejected planet still on the table.
“The significance of discovering Ammonite goes far beyond adding one more distant object,” Dr Shiang-Yu Wang, the corresponding author and a Research Fellow in ASIAA, added in a separate statement. “Ammonite’s orbit tells us that something sculpted the outer Solar System very early on. Whether it was a passing star or a hidden planet, this discovery brings us closer to the truth.”
While still possible, the team believes that this new discovery lowers the chances of the existence of Planet Nine, as it is unclear why the hypothetical planet would cluster the other sednoids, but not Ammonite.
“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,” Dr Yukun Huang of the National Astronomical Observatory of Japan added. “It is possible that a planet once existed in the Solar System but was later ejected, causing the unusual orbits we see today.”
More study of Ammonite and the other sednoids is necessary to further pin down what happened, but having this “fossil” object will help us along the way, and maybe help clear up if Planet 9 exists out there on the edge of our Solar System.
The study is published in Nature Astronomy.
Our solar system stole asteroids from interstellar space when it was young, scientists say
A cache of interstellar asteroids may have been hiding under scientists’ noses for billions of years, researchers say. New research focused on a handful of strange space rocks known as Centaurs. Astronomers have long been puzzled by Cent aurs because their orbits are very unpredictable. The new research suggests that’s because they were stolen by our solar system when it was very young, as stars were closer together in the early days of the solar system.. The discovery of a whole population of asteroids of interstellar origin is an important step in understanding the physical and chemical similarities and differences between solar system-born and interstellar asteroids, co-author Maria Helena Morais said.
A cache of interstellar asteroids may have been hiding under scientists’ noses for billions of years, researchers say.
That’s according to new research focused on a handful of strange space rocks known as Centaurs , which orbit the sun in the neighborhood of Jupiter and Saturn. Astronomers have long been puzzled by Centaurs because their orbits are very unpredictable, with simulations suggesting that they should bang into things or fly out of the solar system . The new research suggests that’s because they were stolen by our solar system when it was very young. With so much less expansion under the universe’s belt, stars were closer together.
“The close proximity of the stars meant that they felt each others’ gravity much more strongly in those early days than they do today,” Fathi Namouni, lead author of the study and an astronomer at Observatoire de la Cote d’Azur in France, said in a statement . “This enabled asteroids to be pulled from one star system to another.”
Related: Photos: Asteroids in deep space
The new research focused on 21 objects in the outer solar system: mostly Centaurs and a few other strange space rocks. Using a computer program, the scientists virtually cloned these objects tens of thousands of times over to understand likely scenarios for their escapades.
According to the researchers, that analysis suggests that the Centaurs’ strange-but-steady orbits are a hint they were born beyond our solar system and trapped here. Scientists have long hypothesized that objects move between solar systems, and saw the first confirmed interlopers in our neighborhood in the past few years, with ‘Oumuamua and Comet Borisov .
Both of those objects only passed through our solar system and weren’t caught by the sun’s gravity. The scientists on the new research think early asteroids may have been more likely to wander into other star systems and get stuck because in the early days of the solar system, with more than 4 billion years less of expansion , things were closer together.
Get the Space.com Newsletter Breaking space news, the latest updates on rocket launches, skywatching events and more! Contact me with news and offers from other Future brands Receive email from us on behalf of our trusted partners or sponsors
And identifying originally interstellar asteroids in our cosmic neighborhood is important because they are much easier to study than objects in distant solar systems.
“The discovery of a whole population of asteroids of interstellar origin is an important step in understanding the physical and chemical similarities and differences between solar system-born and interstellar asteroids,” co-author Maria Helena Morais, an astronomer at Universidade Estadual Paulista in Brazil, said in the same statement. “This population will give us clues about the sun’s early birth cluster, how interstellar asteroid capture occurred, and the role that interstellar matter had in chemically enriching the solar system and shaping its evolution.”
The research is described in a paper published today (April 23) in the journal Monthly Notices of the Royal Astronomical Society.