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Last Updated Sep 27, 2025
Space Simplified Revision Notes for Junior Cycle Science
Revision notes with simplified explanations to understand Space quickly and effectively.
441+ students studying
Space
1. Astronomy
Astronomy: The study of space, stars, planets, and other objects in the universe.
2. Celestial Bodies
Celestial bodies: Naturally made objects outside Earth's atmosphere, e.g., stars, comets, moons, and asteroids.
Universe: Everything that exists, including all space, matter, and energy.
3.Stars
Star: A massive ball of hot gas that produces light and heat. Our Sun is a star.
- Temperature Range: From ten million to three billion degrees Celsius.
- Size Range: From 59,000 km radius to over one million km radius.
- Function: Generates its own heat and light through nuclear fusion.
- Example: The Sun.
4. Planets
Planet: A large object that orbits a star. It does not produce its own light. Examples are Earth, Mars, and Jupiter.
- Clarification: "Cleared the region" means it exerts the most gravitational pull in its orbit.
- Example: Pluto was demoted from planet status because it is not the largest celestial object nearby.
5. Galaxy
Galaxy: A huge group of stars, dust, and gas held together by gravity.
- Example: the Milky Way galaxy
6.Solar System
Solar System: The Sun and all the objects that orbit around it, including planets, moons, asteroids, and comets.
Components:
- 8 planets.
- The Sun at the centre.
Exam Tip! Mnemonic Device: My Very Easy Method Just Speeds Up Naming Planets
- Mercury
- Venus
- Earth
- Mars
- Jupiter
- Saturn
- Uranus
- Neptune
7. Moons
Moon: A natural object that orbits a planet. Earth has one moon.
- Example: Saturn has 50 moons.
8. Asteroids
Asteroid: A small rocky object that orbits the Sun. Most are found in the asteroid belt between Mars and Jupiter.
9. Comets
Comet: A small icy object that orbits the Sun. When close to the Sun, it has a bright tail.
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