- #1
paldin
- 6
- 0
I searched for "definition" and "planet" but found no thread which matched this purpose; if one already exists then it is significantly old, but I will apologize anyways.
It used to be that our solar system had Nine planets. Then some trans-Neptunian object (Eris) forced some astrological society to draw a line in the sand between "planet" and "almost but not quite". For the most part, I enjoy the definition; but I still find it lacking. It's very specific to our solar system. I would suggest some alterations that uphold the spirit but also improve upon the concept. I'm looking for constructive criticism, but positive feedback is okay too. Being that I have not been an Astronomy major, and my knowledge of the subject comes from my general thirst for knowledge; I can't pretend that I'll propose a "final solution" to the planet definition debacle.
In laymen's terms, a planet is a large object that orbits a star. Most people aren't worried much further than that. A satelite orbits a planet and a star produces energy via fusion, asteroids are those small objects nearby or the large objects that wander around (where a comet is a specific kind of asteroid). My assertions will spring from these (simplified)assumptions. Later stated definitions shall override any prior definitions.
An asteroid should be defined as any object massive enough to hold its composition (ie: not a dust cloud). A special asteroid (with what name, "rogue planet"?) would be any object massive enough to fulfill the shape requirement of being a planet, but does not orbit any star.
A satelite (aka moon) should be defined as any object that fulfills the above and orbits a planet.
A planet should be defined as any object: (1) massive enough to form/maintain a generally spherical shape, (2) orbits a star (including binary, etc), and (3) holds the majority of mass within its orbit by a ratio of at least [10] to 1 (where '1' is everything else combined).
Special types of planets include: a dwarf planet lacks either the conditions or mass required to maintain a generally spherical shape; a binary planet is two objects that together hold the requisite ratio to be a planet, and may or may not directly orbit each other around their star; a gas giant (for purposes of being a type of planet) is composed mostly of gasses but lacks sufficient mass to conduct fusion; ...and otherwise meets the other conditions of being a planet.
A star is any object massive enough, and is currently observed, to conduct fusion. A dead star would be any object that is not currently but had at any time enough mass to fuse at least Deuterium (ie: Brown dwarf). Specific kinds of stars (dwarf, giant, etc) would still hold their definitions, but to be in the "star" category at all I suggest this definition.
A black hole is any "object" massive enough to trap light in its orbit/gravitational field. Other objects may also orbit black holes, without a star being present, and maintain their titles.
Galaxies, nebulas, and universes are beyond my scope, but that would be a fun thought exercise as well. How would one explain galaxies to a lay person without simply stating "a collection of stars"?
We still wouldn't consider Pluto a planet, but this way we can easilly classify any object quickly and intuitively. I see no problem with moons never being considered "planets" in their own right, even when they show all the characteristics of what we would expect from a planet. Popular culture agrees; when the Death Star targeted Yavin IV, it needed to first clear a planet and would be targeting a moon. Clearly, the general populace isn't concerned with how we label habital objects, as long as they make intuitive sense. Should I begin lobbying astrological organizations to push for these laymen definitions or do they need refinement first?
It used to be that our solar system had Nine planets. Then some trans-Neptunian object (Eris) forced some astrological society to draw a line in the sand between "planet" and "almost but not quite". For the most part, I enjoy the definition; but I still find it lacking. It's very specific to our solar system. I would suggest some alterations that uphold the spirit but also improve upon the concept. I'm looking for constructive criticism, but positive feedback is okay too. Being that I have not been an Astronomy major, and my knowledge of the subject comes from my general thirst for knowledge; I can't pretend that I'll propose a "final solution" to the planet definition debacle.
In laymen's terms, a planet is a large object that orbits a star. Most people aren't worried much further than that. A satelite orbits a planet and a star produces energy via fusion, asteroids are those small objects nearby or the large objects that wander around (where a comet is a specific kind of asteroid). My assertions will spring from these (simplified)assumptions. Later stated definitions shall override any prior definitions.
An asteroid should be defined as any object massive enough to hold its composition (ie: not a dust cloud). A special asteroid (with what name, "rogue planet"?) would be any object massive enough to fulfill the shape requirement of being a planet, but does not orbit any star.
A satelite (aka moon) should be defined as any object that fulfills the above and orbits a planet.
A planet should be defined as any object: (1) massive enough to form/maintain a generally spherical shape, (2) orbits a star (including binary, etc), and (3) holds the majority of mass within its orbit by a ratio of at least [10] to 1 (where '1' is everything else combined).
Special types of planets include: a dwarf planet lacks either the conditions or mass required to maintain a generally spherical shape; a binary planet is two objects that together hold the requisite ratio to be a planet, and may or may not directly orbit each other around their star; a gas giant (for purposes of being a type of planet) is composed mostly of gasses but lacks sufficient mass to conduct fusion; ...and otherwise meets the other conditions of being a planet.
A star is any object massive enough, and is currently observed, to conduct fusion. A dead star would be any object that is not currently but had at any time enough mass to fuse at least Deuterium (ie: Brown dwarf). Specific kinds of stars (dwarf, giant, etc) would still hold their definitions, but to be in the "star" category at all I suggest this definition.
A black hole is any "object" massive enough to trap light in its orbit/gravitational field. Other objects may also orbit black holes, without a star being present, and maintain their titles.
Galaxies, nebulas, and universes are beyond my scope, but that would be a fun thought exercise as well. How would one explain galaxies to a lay person without simply stating "a collection of stars"?
We still wouldn't consider Pluto a planet, but this way we can easilly classify any object quickly and intuitively. I see no problem with moons never being considered "planets" in their own right, even when they show all the characteristics of what we would expect from a planet. Popular culture agrees; when the Death Star targeted Yavin IV, it needed to first clear a planet and would be targeting a moon. Clearly, the general populace isn't concerned with how we label habital objects, as long as they make intuitive sense. Should I begin lobbying astrological organizations to push for these laymen definitions or do they need refinement first?
