The Solar System | Physics for GCSE/IGCSE - Year 11 PDF Download

Introduction

• The Solar System Overview:
  • The Sun
  • Eight planets
  • Natural and artificial satellites
  • Dwarf planets
  • Asteroids and comets
• The Sun:
  • The Sun is located at the center of the Solar System.
  • It is a star that accounts for over 99% of the solar system's mass.
• Star:
  • A star is a luminous sphere of plasma held together by its own gravity.
  • Stars like the Sun emit light and heat due to nuclear reactions in their cores.

Planets and Dwarf Planets

• There are eight planets and an unknown number of dwarf planets orbiting the Sun. Planets have a strong gravitational field that pulls in nearby objects, excluding natural satellites. In contrast, dwarf planets lack a strong gravitational field to attract nearby objects.
• The 8 planets in our Solar System, listed in order of increasing distance from the Sun, are:
  • Mercury
  • Venus
  • Earth
  • Mars
  • Jupiter
  • Saturn
  • Uranus
  • Neptune

Main Characteristics

• Gravitational Field: Planets have a strong gravitational field that attracts nearby objects, except for natural satellites.
• Dwarf Planets: These celestial bodies do not possess a strong gravitational field to pull in nearby objects.

Satellites

• There are two types of satellites:
  • Natural Satellites
  • Artificial Satellites
• Natural Satellites
  • Some planets have moons that orbit them, such as Earth. Moons are natural satellites.
  • Moons are celestial bodies that orbit planets. For example, Earth's moon is a natural satellite.
• Artificial Satellites
  • Artificial satellites are human-made objects that orbit celestial bodies. For instance, the International Space Station (ISS) orbits Earth and is a notable artificial satellite.
• Asteroids and Comets
  • Asteroids and comets are celestial bodies that orbit the sun.
  • An asteroid, a small rocky object, orbits the Sun. The asteroid belt is located between Mars and Jupiter.

Our Solar System

• The region between Mars and Jupiter hosts the asteroid belt, a collection of rocky objects.
• Comets, composed of dust and ice, follow distinct orbits around the Sun, developing tails as they approach.
• Planetary mnemonic: "My Very Excellent Mother Just Served Us Noodles" helps recall the order of the 8 planets.

Asteroid Belt

• The asteroid belt, found between Mars and Jupiter, comprises numerous rocky remnants.
• These objects vary in size and composition, ranging from small rocky fragments to larger bodies.
• Some asteroids possess irregular shapes due to collisions and gravitational interactions.

Comets

• Comets consist of a combination of dust and ice, distinct from the rocky asteroids in the asteroid belt.
• As comets approach the Sun, the ice within them begins to melt, leading to the formation of a visible tail.
• Comet tails, often gaseous and illuminated by sunlight, can stretch for millions of kilometers.

Planetary Mnemonic

• The mnemonic "My Very Excellent Mother Just Served Us Noodles" aids in remembering the sequence of the planets.
• The first letters of each word correspond to the planets in order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.
• This mnemonic simplifies the process of recalling the planetary order for educational purposes.

Accretion Model of the Solar System

• There are four rocky and small planets: Mercury, Venus, Earth, and Mars. These are the nearest to the Sun.
• There are four gaseous and large planets: Jupiter, Saturn, Uranus, and Neptune. They are the farthest from the sun.

• The differences in the types of planets are determined by the accretion model, which describes the formation of the Solar System.
• The Sun and the Solar System were created approximately 4.5 billion years ago.
• Planets formed from the remaining matter in a disc-shaped cloud surrounding the young Sun.
• Interstellar clouds contained various elements produced by the end of a star's life cycle.
• Gravity caused the nebula to collapse, leading to the formation of a spinning disc.
• Particles within the disc were drawn together by gravity, gradually forming planets.
• The Sun originated from the gravitational collapse of hydrogen clouds known as nebulae.
• Gravitational forces pulled these clouds together, initiating the formation process.
• As the nebula collapsed, it began to rotate around its center, eventually forming the Sun.
• Particles joined together due to gravitational attraction, initiating an accretion process.
• A rotating accretion disc was formed during the emergence of planets.

• The Sun's growth led to higher temperatures, affecting the formation of inner planets.
• Inner planets consist of materials with high melting points like iron, due to the high temperatures near the Sun.
• The inner planets, like Earth and Mars, are primarily composed of materials with high melting temperatures, such as metals like iron.
• Due to the limited heavy elements in the original nebula (only 1%), the inner rocky planets could not grow significantly, remaining small, solid, and rocky.
• In contrast, the outer planets, such as Jupiter and Saturn, formed in cooler regions farther from the Sun. Here, temperatures were low enough for light molecules to exist in a solid state.
• The outer planets were able to grow much larger than the inner planets, incorporating even the lightest element, Hydrogen. These planets are characterized by their large, gaseous, and cold nature.