Astronomy & space · lesson 2 of 4
Solar-system structure and scale
The Sun is a star at the centre of the planetary system. Planets, moons, small bodies, gas and dust form a gravitationally interacting system.
Learn the ideas
Prerequisites: Fractions, ordering and basic gravity.
Architecture
The Sun is a star at the centre of the planetary system. Planets, moons, small bodies, gas and dust form a gravitationally interacting system.
Categories
A planet, a moon and a star are different kinds of object. A moon orbits a larger nonstellar body; stars sustain fusion during their main-sequence phase.
Distance units
An astronomical unit is a defined length close to the mean Earth-Sun distance. Light-years also measure distance, not time.
Scale models
One scale rarely shows both body sizes and orbital distances conveniently. State what is scaled and what has been exaggerated.
Worked examples
What kind of astronomical object is the Sun?
The Sun is the star of the solar system.
A star
What does a light-year measure?
It is the distance light travels in a year under the defined convention.
Distance
Check your understanding
8 questionsDecimals or fractions are accepted for numeric answers. Proofs and written responses use sample answers and require human marking. This is practice, not a protected examination.
Further reading and review references
These are reference links, not copied exercises, institutional endorsement or proof of independent review.