AstronomyLesson 2 of 2 in the course Other Worlds: An Introduction to the Solar System

Solar-System Formation: Nebula, Planet Growth, and Impacts

5 flashcards · 5 quiz questions · 5 match pairs · 4 fill-in sentences · English

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Summary

The planets orbit the Sun in nearly the same plane and travel around it in the same direction. The Sun also spins in that general direction. These orderly patterns suggest that the Sun and planets formed together from a spinning cloud of gas and dust, called the solar nebula.

A useful analogy is a rotating cloud that flattens as it contracts. Material in the cloud tends to settle into a disk, much like pizza dough spreading as it spins. The planets formed within this disk, so their orbits retain a common orientation and direction. These patterns do not show every detail of the formation process, but they are important evidence for a shared origin.

All flashcards

Solar nebula
A spinning cloud of gas and dust from which the Sun and planets formed.
Circumstellar disk
A flattened, rotating cloud of gas and dust surrounding a star.
Planetesimal
A small solid body that can gather with others to help build planets.
Planetary differentiation
The separation of planetary materials into layers according to properties such as density.
Exoplanet
A planet that orbits a star other than the Sun.

Quiz questions

  1. How did planetesimals contribute to planet formation?Answer: They gathered under gravity and collisions, helping build larger bodies.
  2. Which two heat sources helped warm young planets?Answer: Impacts and energy released by radioactive elements.
  3. What does planetary differentiation mean?Answer: Materials separate into layers according to properties such as density.
  4. What can disks around young stars help astronomers investigate?Answer: Conditions in which material may cool and gather into solid bodies.
  5. What can leftover planetesimal fragments do in the present-day solar system?Answer: Collide with established planets and pose hazards.

Based on Astronomy 2e by Andrew Fraknoi, David Morrison, Sidney Wolff (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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