What is a Planet?

What is a planet? based on the dictionary, the planet is a celestial object reflects light from shining as a star and moving around the star. For ordinary people, the planet is a member of the solar system moves around the sun.

For the observer sky, the planet is a celestial object is not twinkling like stars because the planet can not produce light. But for researchers, the definition of planet is not that easy. The observation over the years with various theories give various definitions of the planet. Some quote the definition of planet is as follows:

Geoffry W. Marcy:
Planet is an object that has a mass between that belongs to Pluto and the threshold of combustion deutrium and that formed in orbit around an object that can generate energy through nuclear reactions.

G H A Cole:
planet is a cold object

Gibor Basri:
planet is a spherical non fusor who was born in orbit around a fusor.

Alan Stern & The Levinson:
planet is bound planetary objects in orbit around the multi-star systems and single stars.

Mike Brown:
planet is an object in the solar system more massive than the total mass of other objects in adjacent or similar orbit.


Planet itself comes from the Greek word "Wanderer" or "rover" that is the object of the cold sky, and does not produce energy. The planet can only rely on a large reflective albedonya. As a cold object, the planet does not have a significant source of heat energy in it and was not influenced by temperature. If the brown dwarf stars and thermonuclear processes of internal heat energy supply, the planet's heat energy from outside itself for instance from the parent star. In addition, the interior condition of the planet, is not sufficient to cause the ionization of its constituent atoms.