A Mysterious Object Discovered Beyond Neptune is Moving Around the Sun in the Opposite Direction

### Why the Object is Moving "the Wrong Way" Most planets in the Solar System orbit the Sun in roughly the same plane and in the same direction — counterclockwise when viewed from the North Pole of Earth, writes [EarthSky](https://earthsky.org/space/rubin-retrograde-object-far-solar-system-r631/). This is related to the origin of the Solar System, which formed about 4.6 billion years ago from a rotating cloud of gas and dust. The material gradually coalesced into the Sun, planets, and numerous smaller celestial bodies, inheriting a common direction of rotation. However, there are exceptions. In astronomy, orbits with an inclination exceeding 90 degrees relative to the main plane of planetary orbits are called retrograde. The discovered object R631 has an inclination of 142 degrees. Thus, it not only moves along a highly inclined trajectory but also orbits the Sun in the opposite direction. ### One Orbit Around the Sun Takes Nearly 548 Years R631 was discovered while analyzing observations from the Rubin Observatory, conducted from December 2025 to March 2026. Currently, the object only has a temporary designation. In the future, an official designation will be assigned by the Minor Planet Center. R631 is currently located about 32 astronomical units from the Sun. One astronomical unit corresponds to the average distance between the Earth and the Sun — about 150 million kilometers. In comparison, Neptune orbits the Sun at an average distance of about 30 astronomical units. Preliminary Characteristics of R631 | Orbital Inclination | 142° | | ------------------------------- | ---------------------------- | | Current Distance from the Sun | 32 AU (about 4.8 billion km) | | Orbital Period | 547.84 years | | Closest Approach to the Sun | October 31, 2047 | | Perihelion Distance | 24 AU | | Estimated Diameter | About 100 km | According to preliminary calculations, R631 will reach the closest point to the Sun in its orbit on October 31, 2047. Even then, it will be about 3.6 billion kilometers away from our star. ### It Might Be a Giant Comet Physicist and astronomer Marshall Ubbanks suggested that the diameter of the object could be around 100 kilometers. In terms of size and possible nature, R631 may resemble the giant comet Bernardinelli–Bernstein (C/2014 UN271), one of the largest known comets. If R631 is indeed a cometary body, it could theoretically begin to exhibit activity — for example, releasing gas and dust — as it approaches the Sun. However, this is still just a hypothesis. Observations have not yet determined the exact composition of the object or confirmed its cometary nature. ### Where Such a Strange Orbit Comes From Scientists are considering several possible explanations for the origin of R631. According to one hypothesis, the object may have formed beyond the Solar System and then been captured by the Sun's gravity. Another version suggests that R631 originally formed in our system and moved in the usual direction, but its orbit was radically altered under the influence of a massive celestial body. This body could have been Jupiter, Neptune, or even a star that once passed relatively close to the Solar System. Amateur astronomer Sam Dean considers it most likely that R631 originated from the Kuiper Belt — a vast region of icy objects beyond Neptune's orbit. He hypothesizes that a too-close encounter with Neptune over the last billion years could have made the object's orbit unstable and ultimately changed its direction of motion. ### Is There a Connection to Famous Comets of the Past? Interestingly, an orbital inclination of about 142 degrees has also been observed in other known celestial bodies. For example, a similar orbit was held by the Great Comet of 1882 — one of the brightest objects ever observed in the Earth's sky. This group also includes the Comet Ikeya–Seki, which passed extremely close to the Sun in 1965 and broke into several fragments. Both comets belong to the Kreutz family. Astronomers believe that its members are remnants of one ancient giant comet. However, a coincidence in orbital inclination does not necessarily imply a common origin. Astronomer Tony Dunn conducted computer simulations of the motion of R631 and the Kreutz family comets. The results showed that the discovered object is not related to this family. Thus, the origin of R631 remains a mystery. Further observations will help clarify its orbit, size, and physical properties, as well as understand what gravitational events may have caused it to move around the Sun in the opposite direction.