Discussion Overview
The discussion revolves around the classification of a hypothetical Trans-Neptunian Object (TNO) referred to as "planet 9" and whether it would meet the current criteria established by the International Astronomical Union (IAU) for being classified as a planet. The scope includes theoretical considerations regarding definitions and classifications in astronomy.
Discussion Character
Main Points Raised
- One participant questions what classification a hypothetical TNO "planet 9" would fall under if detected, given it may not fit the IAU's current criteria.
- Another participant suggests that it could be classified as a very large TNO.
- A participant outlines the current IAU definition of a planet, noting the criteria including orbiting the sun, being nearly round, not being a satellite, and having cleared its orbit of debris.
- Concerns are raised about the orbit-clearing criterion, with a participant arguing that objects at such distances may have eccentric orbits and struggle to clear their surroundings, thus questioning their classification as planets.
- Another participant notes that while a 10 Earth mass object may be planet-sized, it cannot be classified as a dwarf planet or a rogue planet if it is in orbit, raising the issue of whether the definitions may need to be adjusted.
Areas of Agreement / Disagreement
Participants express differing views on whether the hypothetical TNO could be classified as a planet under current definitions, indicating a lack of consensus on the classification criteria and the implications of the orbit-clearing requirement.
Contextual Notes
Participants highlight limitations in the current definitions, particularly regarding the orbit-clearing criterion and the implications for objects that may not fit neatly into existing categories.