Our Solar System consists of the Sun and the eight planets, their moons, dwarf planets, asteroids, Kuiper belt objects, Oort Cloud, comets, meteoroids and interplanetary dust.
Facts about Our Solar System
The regions of the Solar System consist of:
- Our Sun
- Four Terrestrial Inner Planets: Mercury, Venus, Earth, Mars
- Asteroid Belt: Composed of small rocky bodies
- Four Gas Giant Outer Planets: Jupiter, Saturn, Uranus, Neptune
- Kuiper belt– Second belt composed of icy objects.
- Oort cloud: Beyond the Kuiper belt
Note: Pluto was demoted in 2006 from a Planet to Dwarf Planet.
How does the Solar System work?
The Sun is the centre of our solar system and celestial bodies such as the planets, their moons, the asteroid belt, comets and other objects revolve around the Sun and are gravitationally bound to it. The Sun contains around 98% of all the material in the Solar System.
The boundaries of the solar system’s known planets fit within a sphere 50 AU in radius. Beyond that is the Oort Cloud which extends to a distance of 100,000 AU. Beyond that is the nearest star system is Alpha Centauri.
Note: The stars are not part of our solar system. Astronomers have discovered that some other stars, besides our own sun, have their own solar systems around them as well!
Our Sun is the largest object in our solar system. It is 4.6 billion years old.
Asteroids are small rocky objects orbiting the sun. They range in size from nearly 1,000 km (600 miles) across to dust particles. They are too small to be considered planets. Most are found in the Asteroid Belt. Asteroids are also called minor planets or planetoids.
Comets are made of ice, frozen gas, dust and rocks. Most comets travel in highly elliptical orbits around the Sun. Most comets are located in the Oort Cloud.
Meteoroids are little chunks of rock and debris in space. The size ranges from a grain of sand up to a boulder. They become meteors (shooting stars) when they fall through a planet’s atmosphere. When they hit the ground are meteorites.
What is a Planet?
The International Astronomical Union (IAU) said that the definition for a planet is now officially known as “a celestial body that:
(a) is in orbit around the Sun
(b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape and
(c) has cleared the neighborhood around its orbit.”
At the same time, new moons are also being discovered, both around existing planets and within these mysterious new worlds. Once the existence of a moon is confirmed and its orbit determined, the moon is given a final name by the International Astronomical Union (IAU), the organization that assumed this task since 1919.
The planets all revolve around the Sun. Six of the eight planets are orbited by natural satellites (moons) after Earth’s Moon and each of the outer planets is encircled by planetary rings of dust and other particles. All the planets except Earth are named after gods and goddesses from Greco-Roman mythology. The three dwarf planets are Pluto, the largest known Kuiper belt object; Ceres, the largest object in the asteroid belt and Eris, which lies in the scattered disc.
Planets in the Solar System:
In order of their distances from the Sun, the planets are:
- Mercury: has no moon
- Venus: has no moon
- Earth: has 1 moon
- Mars: has 2 moons Deimos and Phobos
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Solar System Links:
- The Nine Planets Solar System Tour: Information about each planet and moon in our solar system with many pictures, discussion of the history of its discovery and exploration
- The Virtual Solar System: Visit the Datastore for detailed facts and figures on the planets and moons in our Solar System. Get interactive! Fly through a 3D Virtual Solar System
- Views of the Solar System: Views of the Solar System presents a multimedia adventure unfolding the splendor of the Sun, planets, moons, comets and asteroids.
- Solar System: Learn about our Solar System with KidsAstronomy.com.
- NASA – JPL Solar System Simulator: Online software that generates views of the bodies of our planetary system at any date from any artificial or natural point of observation.
- Solar System Model:
- The Solar System: Source of Picture from rain.org (15 August 2007)
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