Astronomers used a telescope in Hawaii to find a new object on the outer edges of our solar system, helping to fuel evidence of a long-standing theory about Planet Nine, or Planet X.
For years, scientists have theorized about a ninth planet beyond Neptune because of the orbital patterns of smaller objects in the Kuiper Belt, a region of icy objects beyond Neptune. Pluto is considered a Kuiper Belt Object, or KBO. The theoretical planet would be the ninth planet because in 2016 Pluto was downgraded to a dwarf planet after the object Eris was discovered.
ON 95TH ANNIVERSARY OF PLUTO DISCOVERY, ITS HOME OBSERVATORY CELEBRATES SOLAR SYSTEM’S UNDERDOG
On Tuesday, scientists with the Subaru Telescope operated by the National Astronomical Observatory of Japan revealed a fourth member of the sednoids, a group of small bodies with “peculiar orbits.” The findings were published this week in Nature Astronomy.
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.
(NAOJ/ASIAA / FOX Weather)
Nicknamed “Ammonite,” researchers say it could provide more evidence for the hypothetical “Planet Nine” beyond Neptune.
Ammonite has likely been around since the solar system’s infancy and has maintained a stable orbit for about 4.5 billion years, according to the research group. This newly discovered object follows a different orbit than the other sednoids.
TELESCOPE CAPTURES SIGHT OF BRIGHT AURORAS, BUT THESE AREN’T ON EARTH
“The numerical simulations conducted in this study suggest that if Planet Nine exists, its orbit should lie even farther out than previously predicted,” according to a news release from the observatory. “Furthermore, the existence of Planet Nine would also need to explain why Ammonite’s orbit does not cluster with those of the other sednoids.”
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)
(NAOJ)
According to Dr. Fumi Yoshida, of the University of Occupational and Environmental Health and the Chiba Institute of Technology, who led the survey project, Ammonite is too far away from Neptune for major gravitational 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 said. “Understanding the orbital evolution and physical properties of these unique, distant objects is crucial for comprehending the full history of the Solar System.”
According to NASA, “Planet X (Planet Nine) has not yet been discovered, and there is debate in the scientific community about whether it exists.”
