In 2008, astronomers Tadashi Mukai and Patryk Sofia Lykawka proposed the existence of a hypothetical trans-Plutonian planet to explain certain anomalies observed in the Kuiper belt—a region beyond Neptune populated with icy bodies and dwarf planets. Their research suggested that this unseen planet could be influencing the orbital characteristics of trans-Neptunian objects (TNOs).[1]
Proposed Characteristics of the hypothetical planet[]
Mukai and Lykawka's model described a planet with the following attributes:
- Size and Mass: Estimated to be between 30% and 70% of Earth's mass, positioning it between the sizes of Mars and Earth.[2]
- Orbital Distance: An elliptical orbit ranging from 100 to 200 astronomical units (AU) from the Sun. For context, Pluto orbits at an average distance of about 39 AU.[3]
- Orbital Period: A single orbit around the Sun would take approximately 1,000 years.[2][1]
- Inclination: The planet's orbit was proposed to have an inclination between 20° and 40°, relative to the plane of the solar system.[1]
Implications for the Kuiper belt[]
The existence of such a planet could account for several observed peculiarities in the Kuiper belt:
- Orbital excitation: The planet's gravitational influence might explain the high eccentricities and inclinations of certain TNOs, which standard models struggle to justify.[3]
- Detached objects: Objects like Sedna, which have orbits detached from Neptune's gravitational dominance, could have been influenced by this hypothetical planet, placing them on their current distant and elongated paths.[1]
- Kuiper belt edge: The abrupt outer edge of the Kuiper belt at approximately 48 AU might be a result of this planet's past interactions, truncating the distribution of objects in that region.[2]
Search and Current Status[]
At the time of their proposal, Mukai and Lykawka anticipated that advancements in observational technology and dedicated surveys could lead to the discovery of this planet within a decade.[1] However, as of January 2025, no direct observational evidence has confirmed the existence of this trans-Plutonian planet.
References[]
| Hypothetical Bodies, Hypothetical Objects, Hypothetical Regions and Hypotheses | ||
|---|---|---|
| Hypothetical planets | Inner Solar System | Enyo and Bellona • Vulcan • Counter-Earth • Nibiru • Theia • Phaeton • Planet V • Krypton |
| Outer Solar System | Fifth Giant • Uranus Impactor • Triton’s Binary Partner • Haumea Impactor • Quaoar Impactor • Brahma • Vishnu • Oceanus • Hades • Planet Nine • Planet Ten • Rodney's Planet • Planet X • Pickering's Planets • Trans-Plutonian planet • Tyche • Oort cloud planet | |
| Hypothetical Moons | Inner Solar System | Disproven Moons of Mercury • Neith • Petit's moon • Waltemath's moons • Bagby's Moons • Moons of Pallas • Moon of Hebe |
| Outer Solar System | Chiron • Chrysalis • Themis • Sedna I • Varuna I • Herschel's Moons | |
| Hypothetical Stellar Objects | Nemesis • Coatlicue | |
| Hypothetical Regions | Vulcanoid Belt • Hills Cloud • Oort cloud | |
| Hypotheses and Models | Himalia Crash Theory • Iapetus' Ring System • Nibiru cataclysm • Rings of the Moon | |