Orbital Motion
- There are many orbiting objects in our solar system and they each orbit a different type of planetary body
Orbiting Objects or Bodies in Our Solar System Table
- A?smaller?body or object will?orbit?a?larger?body
- For example, a planet orbiting a Sun
- In order to orbit a body such as a star or a planet, there has to be a?force?pulling things?towards?that body
- Gravity?provides this force
- The gravitational force exerted by the larger body on the orbiting object is?always attractive
- Therefore, the gravitational force always acts?towards the centre?of the larger body
- The gravitational force?will cause the body to move and maintain in a?circular path
Gravitational attraction causes the Moon to orbit around the Earth
- Gravity causes different astronomical orbits to orbit certain others
- In general:
- Planets orbit the Sun
- Moons orbit planets
- Comets orbit the Sun
- Artificial satellites to orbit the Earth or any body in the Solar System
Differences in Orbits
Orbits of Planets
- There are several?similarities?in the way different planets orbit the Sun:
- Their orbits are all?slightly elliptical?(stretched circles) with the Sun at one focus (approximately the centre of the orbit)
- They all orbit in the?same plane
- They all travel the?same direction?around the Sun
- There are also a few differences:
- They orbit at?different distances?from the Sun (different orbital radius)
- They orbit at?different speeds
- They all take?different amounts of time?to orbit the Sun
- The?further?away a planet is from the Sun, the?slower?it travels and therefore the?longer?it takes to orbit
The orbits of planets around the Sun
Orbits of Moons
- Moons orbit planets in a?circular path
- Some planets have more than one moon
- The?closer?the moon is to the planet:
- The?shorter?the?time?it will take to orbit
- The?greater?the?speed?of the orbit
Comets
- The orbits of comets are very different to those of planets:
- Their orbits are highly?elliptical?(very stretched) or hyperbolic
- This causes the speed of the comets to change significantly as their distance from the Sun changes
- Not all comets orbit in the same plane as the planets and some don’t even orbit in the same direction
- As the comet approaches the sun, its speed?increases
- As it moves further away from the sun, its speed?decreases
The elliptical orbit of a comet
