The universe is a vast expanse composed of matter and energy that formed after the Big Bang. Understanding its composition and structure is fundamental to Earth Science.
The universe consists primarily of dark energy (68%), dark matter (27%), and ordinary matter (5%). These components work together to shape everything we observe in space. The composition of the universe reveals important clues about its origin and evolution since the Big Bang. The most abundant elements found in the visible universe are hydrogen and helium, which make up most of the composition of matter in the Universe. Other elements like oxygen, carbon, and nitrogen exist in smaller quantities but play crucial roles in forming planets, stars, and life as we know it.
Stars are massive celestial objects that produce light and heat through nuclear fusion. Classification of stars is based on their temperature, luminosity, mass, and spectral characteristics. The main types of stars include main sequence stars like our Sun, red giants, white dwarfs, neutron stars, and supergiants. The spectral classification of stars uses the letters O, B, A, F, G, K, and M to categorize stars based on their surface temperature, with O being the hottest and M being the coolest. Each star type has distinct characteristics that affect its life cycle and eventual fate. For example, massive blue stars burn through their fuel quickly and end in spectacular supernovae, while smaller red dwarfs can shine steadily for billions of years. Understanding these classifications helps scientists study stellar evolution and the broader structure of galaxies. This knowledge forms the foundation of modern astronomy and is essential for students studying Earth Science PDF Grade 11 and higher levels of astronomical science.
