Features of Our Solar System - KS3 Physics

Key Points

• The solar system consists of the Sun (nearest star) and objects orbiting it: planets, asteroids, and comets.
• Planets orbit the Sun in circular paths, while moons orbit planets.
• Asteroids and comets have more oval-shaped orbits.
• The Sun's gravity holds these objects together, causing less massive objects to orbit more massive ones.

Features of the Solar System

• Sun: A medium-sized star at the center, closer to Earth than other stars, appears larger and brighter.
• Solar System Composition:
  • Eight planets
  • Several dwarf planets
  • Gas and dust
• Sun's Gravity: Enormous mass creates a strong gravitational field, causing smaller objects to orbit it.
• Orbits: Planets orbit circularly; asteroids and comets in more oval paths.

Planets

Terrestrial Planets

• Closest to Sun: Mercury, Venus, Earth, Mars
• Characteristics: Made of rock and metal, solid surfaces, known as 'earth-like'.
• Atmospheres: Exist but not suitable for human survival.
• Moons: Earth (1), Mars (2 - Phobos and Deimos)
• Venus: Hottest planet due to greenhouse gases.

Gas Giants

• Planets: Jupiter, Saturn, Uranus, Neptune
• Features: Large size, composed mainly of hydrogen and helium, surrounded by rings and moons.
• Jupiter: Largest planet, 79 moons, visible moons with binoculars.
• Saturn: 82 moons, notable ring system.

Relative Sizes of Planets

• Visual comparisons using everyday objects like fruits and vegetables.

Asteroids, Comets, and Dwarf Planets

Asteroids

• Location: Between terrestrial planets and gas giants, mainly in the asteroid belt between Mars and Jupiter.
• Composition: Rock and metal, smaller than planets.

Dwarf Planets

• Examples: Pluto, Eris, Haumea, Makemake, Ceres
• Characteristics: Too small to be considered full planets, Pluto reclassified from a planet.

Comets

• Nature: Icy objects with highly elliptical orbits, form glowing tails when near the Sun.

Orbits

• Gravitational Forces: Objects attract each other; larger mass means stronger force.
• Newton's Thought Experiment: Explains gravitational orbits.

Artificial Satellites and Space Probes

• Artificial Satellites: Orbit Earth, used for navigation, Earth observation, weather monitoring, communications.
• Space Probes: Robotic spacecraft exploring outer space, have visited other planets, moons, or comets.
• Example: Philae lander on comet 67P via Rosetta probe.

Additional Information

• Voyager 1: Carries an item for potential alien discovery.