SNC1W The Solar System

The Solar System Overview

  • The solar system encompasses all celestial bodies, including:

    • 8 planets

    • Their moons

    • Billions of other smaller celestial objects

Distances in the Solar System

  • Distances are measured in astronomical units (AU).

    • 1 AU = approximately 150,000,000 km (average Earth-Sun distance)

Planetary Distances

  • Distances of planets from the Sun:

    • Mercury: 0.39 AU

    • Venus: 0.72 AU

    • Earth: 1.0 AU

    • Mars: 1.52 AU

    • Jupiter: 5.20 AU

    • Saturn: 9.57 AU

    • Uranus: 19.16 AU

    • Neptune: 30.07 AU

    • Pluto (Dwarf planet): 30.18 AU

  • Structure includes the Kuiper Belt (30-50 AU) and the Asteroid Belt (2.2-3.2 AU).

Structure of the Sun

  • The Sun is an average star, essential for life on Earth due to its energy.

  • It is composed of layers:

    • Core: Site of nuclear fusion; approximately 15,000,000 °C.

    • Radiative Zone: Energy moves slowly over millions of years.

    • Convective Zone and Atmosphere: Includes the chromosphere and corona, with the latter extending millions of kilometers into space.

Sun's Surface Characteristics

  • The photosphere is the visible surface that appears textured, resembling boiling liquid due to convection.

  • Sunspots are cooler, dark spots caused by magnetic field disturbances; the largest observed is 36 times Earth's surface area.

  • Solar flares: Quick, powerful energy releases of gas and particles; related to sunspots.

  • Solar prominences: Slow eruptions with lower energy gas.

Solar Winds and Earth Impacts

  • Solar winds affect Earth’s magnetic field, especially at the poles, leading to phenomena such as:

    • Aurora Borealis (Northern Lights) and Aurora Australis (Southern Lights).

  • Solar winds increase during solar flares and prominences.

Components of the Solar System

  • Beyond the 8 planets, numerous celestial objects include:

    • Planets: Must orbit a star, be round due to gravity, and dominate their orbit.

    • Dwarf Planets: Spherical but do not dominate their orbits (e.g., Pluto).

    • Recognized dwarf planets: 5, with over 2000 suspected existing ones.

  • Asteroids: Small rock-and-metal bodies, primarily in the asteroid belt between Mars and Jupiter.

  • Meteoroids: Smaller than asteroids; can create meteors when entering atmosphere and meteorites if they reach the surface.

  • Comets: Large icy bodies with orbits taking a long time; develop tails when close to the Sun due to sublimation.

Motions in the Solar System

  • All bodies orbit the Sun counterclockwise; orbits are elliptical.

  • Orbital speed: Smaller orbits move faster; larger orbits move slower.

  • Example orbital durations:

    • Mercury: 88 days

    • Earth: 365.25 days

    • Mars: 687 days

Earth's Motion and Seasons

  • Earth rotates on its axis (one rotation per day) and tilts at 23.5° resulting in seasons.

  • Solstices:

    • Summer: June 21 (longest day)

    • Winter: December 21 (shortest day)

  • Equinoxes: September 21 (autumnal) and March 21 (vernal), when day and night are equal.

The Moon's Motion

  • The Moon orbits Earth and goes through 8 phases over about 4 weeks.

  • Eclipses:

    • Solar eclipses occur when the Moon blocks the Sun.

    • Lunar eclipses occur when Earth blocks sunlight from reaching the Moon.

  • Tides: Caused by gravitational interactions between the Earth and Moon; includes 'high' and 'low' tides. Bay of Fundy is noted for having some of the largest tides.