The eight planets in our Solar Definable part of the universe that can be open, closed, or isolated. An open system exchanges both matter and energy with its surroundings. A closed system can only exchange energy with its surroundings; it has walls through which heat can pass. An isolated system cannot exchange energy or matter with, from closest to the Our parent star. The structure of Sun's interior is the result of the hydrostatic equilibrium between gravity and the pressure of the gas. The interior consists of three shells: the core, radiative region, and convective region. Image source: http://eclipse99.nasa.gov/pages/SunActiv.html. The core is the hot, dense central region in which the to the farthest are Mercury, Venus, Earth,Mars, Jupiter, Saturn, Uranus, Neptune.
Phyllis Lugger created this stellar mnemonic to remember the 8 planets and in order: *My Very Educated Mother Just Served Us Nachos.(http://www.aas.org/cswa/bulletin.board/2006/08.25.06.html)
When Pluto was a The term "planet" originally comes from the Greek word for "wanderer" since these objects were seen to move in the sky independently from the background of fixed stars that moved together through the seasons. The IAU last defined the term planet in 2006, however the new definition has remained controversial., there were other mnemonic devices to remember the planets: