Nebular Hypothesis: Planet Formation from Solar Cloud

The question asks to identify the theory that explains the formation of planets from a cloud of material surrounding a young Sun. This process is a fundamental concept in understanding our solar system's origin.

Understanding the Nebular Hypothesis

The Nebular Hypothesis is the most widely accepted scientific model for how planets form within a solar system. It proposes that:

• Planets were formed out of the leftover material from the formation of a star, in this case, the young Sun.
• This material was initially a vast, rotating cloud of gas and dust known as a solar nebula or solar cloud.
• As gravity caused this cloud to collapse, most of the mass concentrated at the center, eventually igniting to become the Sun.
• The remaining gas and dust flattened into a spinning disk around the young Sun, called a protoplanetary disk.
• Within this disk, particles of dust began to stick together, gradually growing into larger clumps (planetesimals).
• Through collisions and accretion over millions of years, these planetesimals merged to form the planets, moons, asteroids, and other bodies in the solar system.

Therefore, the Nebular Hypothesis directly addresses the formation of planets from a surrounding cloud of material around a young Sun.

Evaluating Other Theories

Let's look at why the other options are not the correct explanation for this specific scenario:

• Collision Theory: This theory typically explains the formation of the Moon through a massive impact with Earth or describes how planets might grow by colliding with smaller bodies, but it doesn't describe the initial formation of planets from a general cloud.
• Binary Star Hypothesis: This older idea suggested our Sun had a companion star, and planets formed from material pulled from one of the stars during a close encounter. This is different from forming from a single cloud surrounding the Sun.
• Big Bang Theory: This is the leading cosmological model for the universe's origin itself, describing how the universe began from an extremely hot, dense point about 13.8 billion years ago. It explains the origin of elements and the large-scale structure of the universe, but not the specific formation of planets within a solar system from a local nebula.

Based on the scientific understanding of solar system formation, the Nebular Hypothesis is the theory that explains planets forming out of a cloud of material surrounding a young Sun.