Solar nebula

Definition

A solar nebula is a rotating disk of gas and dust from which the Sun and planets formed about 4.6 billion years ago. It is the initial stage in the development of a solar system, where gravitational forces cause material to coalesce into various celestial bodies.

5 Must Know Facts For Your Next Test

1. The solar nebula hypothesis explains the formation and evolution of the Solar System.
2. The majority of the mass in the solar nebula was concentrated at its center, forming the Sun.
3. Planetesimals, small solid objects, formed within the solar nebula and eventually merged to create planets.
4. The inner part of the solar nebula was hotter, leading to different planetary compositions compared to the cooler outer regions.
5. Observations of other protoplanetary disks around young stars support our understanding of how solar nebulas evolve into planetary systems.

Review Questions

• What is a solar nebula and what role does it play in forming a solar system?
• How do planetesimals form within a solar nebula?
• Why do inner planets have different compositions compared to outer planets in the context of a solar nebula?

Related terms

Protoplanetary Disk: A rotating circumstellar disk of dense gas surrounding a young newly formed star.

Planetesimal: A small body from which a planet originated in the early stages of development of the Solar System.

Accretion Disk: A structure formed by diffused material in orbital motion around a massive central body.