MYP Physics The Solar System Notes

The Solar System Is A Gravitational System With Distinct Types Of Objects

1. The solar system is the collection of objects bound together by the Sun's gravity.
2. It includes the Sun (a star), planets, dwarf planets, moons, asteroids, comets, and clouds of small icy bodies beyond Neptune.
3. At the center is the Sun, which contains most of the solar system's mass and therefore dominates the motion of everything else.
4. The further an object is from the Sun, the weaker the Sun's gravitational pull, and the longer its orbital period.

Observing the Sky: Early Ideas About the Solar System

1. Humans have observed the sky long before modern science developed.
2. Early observers noticed regular patterns in the motion of the Sun, Moon, and stars.
3. The Sun appears to rise in the east and set in the west every day.
4. Stars appear fixed relative to one another over short timescales.
5. These repeated observations encouraged early models to explain the structure of the solar system.

What is a Star?

1. A star is a massive, spherical ball of hot gases, mainly hydrogen and helium.
2. Stars emit their own light and energy, unlike planets, which reflect light.
3. Stars are not all the same.
4. They vary in several important ways:
   1. Temperature
   2. Colour
   3. Mass
   4. Size
   5. Brightness (luminosity)
5. These properties are related:
   1. More massive stars are usually hotter and brighter
   2. Smaller stars tend to be cooler and dimmer

Star Colour and Temperature

1. Blue stars
   1. Hottest stars
   2. Surface temperature above 10,000 K
2. Yellow stars
   1. Medium temperature
   2. Example: The Sun (~5800 K)
3. Red stars