Celestial Bodies (Stars, Galaxies, Comets, Asteroids) - SS1 Physics Lesson Note

Celestial bodies are objects in space that exist outside the Earth's atmosphere. They include stars, galaxies, comets, and asteroids. Here's a brief description of each:

1. Stars: Stars are massive, luminous spheres of hot gas that emit light and heat through nuclear fusion. They are the fundamental building blocks of galaxies and serve as sources of energy. Stars vary in size, temperature, and brightness. Our Sun is a star and is the closest one to Earth.

2. Galaxies: Galaxies are vast systems of stars, gas, dust, and other celestial objects bound together by gravity. They come in different shapes and sizes, such as spiral galaxies, elliptical galaxies, and irregular galaxies. The Milky Way, which is the galaxy containing our solar system, is a spiral galaxy.

3. Comets: Comets are icy bodies composed of a mixture of frozen gases, dust, and rocky material. They originate from the outer regions of the solar system and have highly elliptical orbits. When a comet approaches the Sun, the heat causes the icy nucleus to vaporise, creating a glowing coma and a tail that points away from the Sun.

4. Asteroids: Asteroids are rocky objects that orbit the Sun, primarily found in the asteroid belt between Mars and Jupiter. They range in size from small boulders to several hundred kilometres in diameter. Most asteroids are irregularly shaped and composed of rock and metal.

These celestial bodies play significant roles in the study of astronomy and our understanding of the universe. They provide insights into stellar evolution, galactic structures, the formation of planetary systems, and the history of our solar system. Observing and studying celestial bodies help scientists unravel the mysteries of the universe and expand our knowledge of its vastness and complexity.