Orbiting Bodies

Exam code: 5054

Written by: Ashika|Reviewed by: Caroline Carroll|Updated 2 July 2026

Over many years, data about all the planets, moons and the Sun have been collected
This is not just for general interest, but to indicate:
- Factors that affect conditions on the surface of the planets
- Environmental problems that a visit (using manned spaceships or robots) would encounter

planet	orbital distance from Sun / million km	orbital period	density / kg/m³	surface temperature / °C	surface gravitational field strength / N/kg
Mercury	57.9	88 days	5427	350	3.7
Venus	108.2	225 days	5243	460	8.9
Earth	149.6	365 days	5514	20	9.8
Mars	227.9	687 days	3933	–23	3.7
Jupiter	778.6	11.9 years	1326	–120	23.1
Saturn	1433.5	29.5 years	687	–180	9.0
Uranus	2872.5	75 years	1271	–210	8.7
Neptune	4495.1	165 years	1638	–220	11.0

Worked example

State and explain the relationship between the distance of a planet from the Sun and its

(a) surface temperature

(b) orbital period

Answer:

(a)

The relationship between distance from the Sun and surface temperature is...

This can be seen in the data as...

The planets closest to the Sun are the hottest e.g. Mercury has a surface temperature of 350°

(Note: Venus has the hottest surface temperature due to its dense atmosphere which traps heat)

The planets furthest from the Sun are the coldest e.g. Neptune has a surface temperature of −220°C

Explanation:

The planets nearer to the Sun receive a greater proportion of the emitted heat radiation compared to the further planets

(b)

The relationship between distance from the Sun and orbital period is...

This can be seen in the data as...

The planets closest to the Sun have the shortest orbital periods e.g. Mercury completes one orbit in 88 days
The planets furthest from the Sun have the longest orbital periods e.g. Neptune completes one orbit in 165 years

Explanation:

The Sun's gravitational field strength is strongest at Mercury and decreases with distance
Therefore, the planets which are closer to the Sun travel faster than the planets which are farther away
So, the closest planets move faster and have a shorter distance to travel, meaning they complete orbits in a quicker time

(c)

The relationship between distance from the Sun and density is...

This can be seen in the data as...

Explanation:

The four planets nearest to the Sun must have formed in the hotter inner regions of the early Solar System where higher density material (rocks & metals) collected
The four planets furthest from the Sun must have formed in the cooler outer regions of the early Solar System where lower density material (water and gases) collected

Analysing Orbits