The Solar System
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Planets: The planet count in our solar system has gone as high as 15 before new discoveries prompted a fine tuning of the definition of a planet. The most recent change was in 2006 when scientists reclassified Pluto as a new kind of object - a dwarf planet. Dwarf Planets: This new class of worlds helps us categorize objects that orbit the Sun but aren't quite the same as the rocky planets and gas giants in our solar system. There could be hundreds more of these small worlds far out there waiting to be discovered.
A planet (from Ancient Greek αστήρ πλανήτης (astēr planētēs) , meaning "wandering star") is an astronomical object orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity , is not massive enough to cause thermonuclear fusion , and has cleared its neighbouring region of planetesimals . [ 1 ] [ 2 ] The term planet is ancient, with ties to history , science , mythology , and religion . The planets were originally seen by many early cultures as divine, or as emissaries of deities . As scientific knowledge advanced, human perception of the planets changed, incorporating a number of disparate objects. In 2006, the International Astronomical Union (IAU) officially adopted a resolution defining planets within the Solar System . This definition has been both praised and criticized, and remains disputed by some scientists because it excludes many objects of planetary mass based on where or what they orbit.
The Solar System [ a ] consists of the Sun and its planetary system of eight planets , their moons , and other non-stellar objects . It formed 4.6 billion years ago from the gravitational collapse of a giant molecular cloud . The vast majority of the system's mass is in the Sun, with most of the remaining mass contained in Jupiter .
Our solar neighborhood is an exciting place. The Solar System is full of planets, moons, asteroids, comets, minor planets, and many other exciting objects. Learn about Io, the explosive moon that orbits the planet Jupiter, or explore the gigantic canyons and deserts on Mars. What Is The Solar System?