Our Solar System

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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.

Solar System Picture

Facts about Our Solar System

* Age: 4.6 million years old.
* Number of Stars: 1 (Our Sun)
* Number of Planets: 8
* Number of Dwarf Planets: 5
* Number of Comets: Over 3000
* Number of Asteroids : Over 550,000.
* Nearest Star: Proxima Centauri
* Diameter: 10 light hours at the speed of light

Composition

The regions of the Solar System consist of:

  1. Our Sun – closest star to Earth
  2. Four Terrestrial Inner Planets: Mercury, Venus, Earth, Mars
  3. Asteroid Belt: Composed of small rocky bodies
  4. Four Gas Giant Outer Planets: Jupiter, Saturn, Uranus, Neptune
  5. Kuiper belt– Second belt composed of icy objects.
  6. Oort cloud: Beyond the Kuiper belt

Note: Pluto was demoted in 2006 from a Planet to Dwarf Planet.

Within the Solar System you can also find meteoroids, comets, asteroids, satellites of the planets and the interplanetary medium.

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!

Sun

Our Sun is the largest object in our solar system. It is 4.6 billion years old. It is the Solar System’s star.

Asteroids

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

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

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 the Name of the Solar System?

It is usually referred to as ‘the Solar System’. Solar means ‘of the Sun’ and System refers all the bodies that are caught in its gravitational field. The Sun has a pulling force known as gravity that keeps the planets flying off into space.

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. Astronomers are believe there is a Planet Nine and they are searching for it.

Dwarf Planets

The five dwarf planets are:

  1. Pluto, the largest known Kuiper belt object
  2. Ceres, the largest object in the asteroid belt
  3. Eris, which lies in the scattered disc.
  4. Haumea, its size is about one-third that of Pluto.
  5. Makemake – perhaps the largest Kuiper belt object

Planets in the Solar System:

In order of their distances from the Sun, the planets are:

  1. Mercury: has no moon
  2. Venus: has no moon
  3. Earth: has 1 moon
  4. Mars: has 2 moons Deimos and Phobos
  5. Jupiter
  6. Saturn
  7. Uranus
  8. Neptune.

There are many moons in the Solar System. Largest moon is Ganymede (Jupiter) followed by Titan (Saturn) and then Callisto (Jupiter).

Kuiper Belt

It is located between 30 and 50 AU from the Sun. First spacecraft to explore the Kuiper Belt was NASA’s New Horizons, which flew past Pluto on 14 July 2015.

Oort Cloud

Oort Cloud is the area between 50,000 (0.8 Light Years) to 200,000 AU (3.2 Light Years) from Earth. Spacecraft have not reached the Oort Cloud area. At present, Voyager 1 is the farthest and fastest spacecraft. It will reach it in 300 years time.

Location

Our SolarSystem is located in the Orion-Cygnus Arm in the Milkyway Galaxy.

Note: 1 AU (Astronomical Unit) is the distance from Earth to the Sun, which is 150,000,000 km (93 million miles).

1 Light year is about 63241 AU, which is about 9 trillion km (6 trillion miles).

 Solar System Pic          Did you know?

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