The Solar System, Stability of Orbital Motions + Satellites

How many planets are in our solar system?

8

What are the 4 rocky planets?

Mercury, Venus, Earth and Mars

What are the 4 gas planets?

Jupiter, Saturn, Uranus and Neptune

What is the moon an example of?

A natural satellite

What are artificial satellites?

Man-made satellites used to observe the Earth.

What other objects beside planets orbit the sun?

Comets and asteroids.

What are asteroids made up of?

Rocks

Where is the asteroid belt?

Between Mars and Jupiter

What are comets made up of?

Dust and ice

What is our galaxy called?

The Milky Way

What is the speed of light?

300 million m/s

What is the sun?

A star mostly made up of hydrogen and helium.

What is a nebula?

A giant ball of gas and dust formed by gravitational attraction.

What happens when a nebula collapses?

The centre becomes very dense and hot and starts to rotate.

What is the stage after nebula?

Protostar

What happens when the core of a protostar becomes hot enough?

Hydrogen nuclei undergo nuclear fusion to form helium nuclei.

What makes the centre of a protostar hot?

More particles are pulled close together increasing the density so there are more frequent collisions between particles.

What is the stage after protostar?

Main sequence star

Why are stars at equilibrium?

Gravity acts inwards and the pressure formed by fusion acts outwards, making the star stable.

What happens when temperature of a star increases?

Outward pressure increases as the star expands.

What are the 4 stages following the main sequence star stage of a star similar in size to the sun?

Red giant, planetary nebula, white dwarf and black dwarf.

What is a red giant and how does it occur?

After billions of years the hydrogen fuel runs out so the star’s core shrinks and heats, inward force of gravity increases so the star becomes a red giant when the core is hot enough for helium to fuse into heavier elements. The energy released by re-ignited fusion reaction causes the outer layers to expand and cool.

What are examples of heavier elements produced by fusion in a red giant?

Oxygen and carbon.

What is a white dwarf and how does it occur?

Once helium in the core runs out fusion stops, the star becomes unstable and collapses under its own gravity leaving a white dwarf which is cooling down.

When does a star become a black dwarf?

When the star has lost significant amounts of energy, it continues to cool until it eventually can’t be seen.

What are the 3 stages of stars larger than the sun?

Red supergiant, supernova to neutron star or black hole.

What is a red super giant and how does it occur?

After millions of years the hydrogen fuel for fusion runs out so the star begins to fuse helium into carbon and then even heavier elements this causes the outer part of the star to expand and the surface cools.

What is a supernova and how does it occur?

Once fusion reactions can’t continue the core of the star suddenly collapses and outer layers are blown away in a giant explosion called a supernova. The outer debris is ejected into space forming new nebulas which can form new stars.

How does a neutron star form?

After a supernova the dense body of a neutron star remains which continues to collapse under gravity until it forms a black hole.

What is a black hole?

An extremely dense object which has a extremely strong gravitation pull.

What is nuclear fusion?

When two hydrogen nuclei collide with enough energy they fuse into a helium nuclei.

How are heavier elements formed?

During a supernova the elements left over from fusion are expelled and combine with each other under the extreme pressure and temperatures.

What do objects in a circular object have?

A constant speed but constantly changing direction so constantly changing velocity.

How do planets all orbit the sun?

Their orbits are somewhat elliptical and they all orbit the same plane in the same direction.

How are planets orbit around the sun different?

They orbit at different distances and speeds so take different amounts of time to orbit.

What is a moons orbit like?

They have a circular path around a planet, the closer it is to the planet the greater the speed and the shorter the time.

What happens if the speed of a satellite is too large?

The radius of the orbit increases so the satellite moves further from the object it’s orbiting, the satellite could leave the object’s gravitational field but only if the speed is fast enough or their is continuous force acting on it.

What happens if the speed of a satellite is too small?

The radius of the orbit will decrease and the satellite will move closer to the object it’s orbiting, the satellite may spiral inwards towards the object if a continuous force is acting on it.

If an artificial satellite in a stable orbit changes radius what must happen?

Its speed must change.

What happens if a satellite is moved further away from the object to an orbit with a larger radius?

Force of gravity decreases and so does orbital speed so the orbital period increases.

What happens if a satellite is moved closer to the object to an orbit with a smaller radius?

Force of gravity increases and so does orbital speed so the orbital period decreases.

What is the orbit of a comet?

Elliptical so the speed of the comet changes significantly as the distance changes.

What happens as a comet approaches the sun?

It loses gravitational potential energy and gains kinetic energy causing the comet to speed up creating a slingshot effect so the body is flung back into space. As it moves way from the sun it will slow down eventually finishing its orbit.