Planet Formation Process: Accretion Explained

The question asks to identify the specific process responsible for building planets through the joining of smaller space objects.

Understanding Planet Growth

Planet formation is a complex process that occurs over millions of years. In the early stages of a solar system, vast disks of gas and dust surround a young star. Within these disks, tiny particles begin to clump together.

The Role of Accretion

Accretion is the scientific term for the process where small celestial bodies, like dust grains and pebbles, collide and stick together. These initial clumps grow larger, attracting more material through gravitational attraction. As they grow into larger bodies called planetesimals, they continue to collide and merge, eventually forming protoplanets and then full-fledged planets.

Key aspects of accretion in planet formation include:

• Initial sticking of small particles (dust, ice).
• Growth into larger objects (planetesimals).
• Gravitational attraction drawing more matter.
• Merging of bodies to form planets in protoplanetary disks.

This process explains how planets gradually assemble from smaller building blocks in space.

Analyzing Other Options

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

• Fragmentation: This refers to the breaking apart of celestial bodies, the opposite of sticking together.
• Degassing: This is the process where gases are released from a planet's interior, often contributing to its atmosphere, but it's not how the planet itself is built from smaller pieces.
• Differentiation: This occurs later in a planet's formation when heavier elements sink to the center to form a core, while lighter elements form the outer layers. It describes the internal structure, not the initial growth process.

Therefore, the growth of planets by the collision and sticking of small celestial bodies is accurately described as accretion.