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1.2Unit 3: The Solar System and energy

Formation of the Solar System

5 min read 8 parts Lesson 2 of 7 2 quizzes

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Lesson summary

1.2 Formation of the Solar System — CHECKPOINT EARTH AND SPACE 0893 notes: Explain how scientists think the Solar System formed from a nebula and how models and evidence support the hypothesis.Orbit — all the planets follow a path around the Sun in the same directionSpin — the Su…

  • Same plane
  • No witnesses
  • Evidence first
  • Hypothesis first
  • Star formation
  • Our Solar System

Section 1 of 8Evidence about the Solar System

  • Orbit
    • all the planets follow a path around the Sun in the same direction
  • Spin
    • the Sun and all the planets except Venus and Uranus spin on their axes in the same direction
  • Moons
    • most moons orbit their planets in the same direction as the planets orbit the Sun
  • Same plane
    • all the planets orbit in the same plane, so the Solar System looks flat
  • Evidence = facts from observations or experiments that support or go against an idea

Section 2 of 8Ways scientists solve the problem

  • No witnesses
    • nobody observed the Solar System forming, so scientists use indirect methods
  • Evidence first
    • look for evidence and then explain what has been found
  • Hypothesis first
    • think of a testable idea, then look for evidence to support it
  • Hypothesis = a testable idea or theory

Section 3 of 8Nebulae and young stars

  • Nebula = a cloud of dust and gas in space
  • Star formation
    • scientists can see distant stars forming from nebulae in other parts of space
  • Discs
    • some young stars have a flat disc of dust around them
  • Our Solar System
    • scientists think it formed in this way about 4.6 billion years ago

Section 4 of 8Forming stars and planets by gravity

  1. Particles of dust and gas each have their own very weak gravity.
  2. They pull on each other and stick together, so their total mass increases.
  3. As the mass increases, the strength of gravity increases, so more dust and gas is attracted.
  4. A small ball forms and gradually gets bigger.
  5. A ball that grows beyond a certain size gets hot enough to become a star.
  6. A ball that stays smaller becomes a planet.

Section 5 of 8Time scale and Jupiter

  • Time
    • it takes millions of years to form a star or a planet
  • Jupiter
    • scientists think it almost reached the size needed to be a star

Section 6 of 8Using models

  • Model = a way of representing something that is difficult to observe directly
  • Computer models
    • scientists put known laws of physics into a program and start with a cloud of dust and gas
  • Prediction
    • the computer predicts that a star forms, surrounded by planets
  • Reason for models
    • star and planet formation takes millions of years, and a model can speed this up
  • Limitation
    • models are not real, so they may not be accurate

Section 7 of 8Evidence for and against the hypothesis

  • Supports
    • most of the facts about the Solar System agree with the hypothesis
  • Contradicts
    • Venus spinning the opposite way to the other planets seems to go against it
  • Status
    • most but not all of the evidence supports it, and it cannot be fully tested by experiments

Section 8 of 8More from the specification

  • Nebular hypothesis
    • The solar system formed approximately 4.6 billion years ago from a vast rotating cloud of gas and dust (nebula).
  • Gravitational collapse
    • Gravity pulled particles of dust and gas together, converting gravitational potential energy into thermal energy at the dense central protostar.
  • Planetary accretion
    • Colliding rocky and icy objects coalesced under mutual gravitational forces into protoplanets orbiting the newly formed Sun.
  • Planetary rotation axes
    • Conservation of angular momentum caused the collapsing nebula to flatten into a spinning accretion disk, setting the rotational axis of planets.
  • Force
    • A push or pull measured in newtons.

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