Stellar Evolution and Life Cycles Stars are formed from massive clouds of gas and dust called nebulae . Gravity causes these clouds to contract and spin, formin...
Stars are formed from massive clouds of gas and dust called nebulae. Gravity causes these clouds to contract and spin, forming a protostar at the center. As the protostar's core temperature increases, nuclear fusion begins, converting hydrogen into helium and releasing vast amounts of energy. This marks the start of a star's main sequence life cycle.
During the main sequence, stars fuse hydrogen into helium in their cores. The star's mass determines its lifespan, with more massive stars burning through their fuel faster. When the hydrogen fuel is depleted, the core contracts while the outer layers expand, creating a red giant. In this phase, heavier elements like carbon and oxygen are fused.
The final fate of a star depends on its mass:
The Big Bang theory explains the origin and evolution of the Universe. According to this theory, the Universe began from an extremely hot and dense singularity around 13.8 billion years ago, expanding and cooling to form the current structure of galaxies, stars, and planets.
Evidence for the Big Bang includes the cosmic microwave background radiation (CMBR), which is the residual radiation from the early hot and dense universe. Additionally, the redshift of light from distant galaxies indicates that the Universe is expanding, supporting the Big Bang model.
Our Solar System formed around 4.6 billion years ago from a rotating cloud of gas and dust. Gravity caused the cloud to collapse, forming the Sun at the center and a disk of material that eventually formed the planets, asteroids, and comets.
Planets and moons orbit the Sun and other planets in elliptical paths, governed by gravitational forces. The concept of exoplanets – planets orbiting stars other than our Sun – has revolutionized our understanding of planetary systems in the Universe.
The study of space physics broadens our understanding of the cosmos, from the formation and evolution of stars to the origins of our Solar System and the existence of exoplanets beyond.