Two prominent theories that explain the origin of the solar system are the Nebular Hypothesis and the Capture Theory.
- Nebular Hypothesis: The Nebular Hypothesis, also known as the Nebular Cloud Theory, is the most widely accepted theory for the formation of the solar system. It proposes that the solar system formed from a rotating cloud of gas and dust called the solar nebula. The key steps involved in this theory are as follows:a. Collapse: The solar nebula collapsed under its own gravity due to a disturbance, such as a nearby supernova explosion or a passing star’s gravitational pull. As the cloud collapsed, it began to rotate faster, forming a spinning disk-shaped structure with the central region becoming denser.b. Protostar Formation: The dense central region of the collapsing nebula, called the protosun or protostar, grew hotter and denser over time. The protostar eventually reached a point where the pressure and temperature at its core were sufficient for nuclear fusion to begin, igniting the star and becoming the Sun.c. Accretion and Planetesimal Formation: Within the spinning disk of the nebula, small particles of dust and gas collided and stuck together due to mutual gravitational attraction. These collisions led to the formation of larger bodies called planetesimals, ranging in size from kilometers to hundreds of kilometers in diameter.d. Planet Formation: Planetesimals continued to collide and merge, gradually forming protoplanets, which were larger bodies with sufficient mass to exert significant gravitational attraction. Through further accretion and the clearing of their orbital paths, protoplanets eventually evolved into the planets we know today.
- Capture Theory: The Capture Theory suggests that some objects in the solar system, such as moons and asteroids, were formed elsewhere in the universe and later captured by the gravitational pull of the Sun or larger planets. According to this theory:a. Interstellar Object Capture: It proposes that certain objects, such as asteroids or comets, originated outside the solar system as independent bodies. These objects were either drifting through interstellar space or were part of another planetary system.b. Gravitational Capture: As these objects ventured close to the Sun or a massive planet, the strong gravitational force of the Sun or planet influenced their trajectory. The object’s path was altered, causing it to be captured into a stable orbit around the Sun or a specific planet.c. Orbital Adjustment: Once captured, the object’s orbit might have undergone adjustments due to interactions with other celestial bodies in the solar system, leading to its current orbit and position.
The Capture Theory provides an explanation for the presence of certain objects in the solar system that have different characteristics from those formed by the Nebular Hypothesis. However, the Capture Theory is not as widely supported as the Nebular Hypothesis, and further research and observations are needed to validate its mechanisms.