P16

Question 1

What is our solar system made up of

Answer 1

The sun
8 planets 
Dwarf planets e.g Pluto
Moons
Artificial satellites e.g ISS

Question 2

What are moons

Answer 2

Natural satellites that orbit planet

Question 3

What are the 8 planets in order from the sun

Answer 3

Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune

Question 4

What is our solar system a part of

Answer 4

It’s part of the milky way galaxy

A collection of billions of stars held together by gravity

Question 5

What is the simple life cycle of a star

Answer 5

Cloud of gas ( nebula )
Protostar
Main sequence star

Stars same size as sun:
Red giant
White dwarf
Black dwarf

Stars much bigger than sun:
Red super giant
Supernova
Neutron star or black hole ( only very very big stars )

Question 6

First stage of star cycle

Answer 6

Cloud of dust and gas called nebula

Force of gravity pulls them together to form protostar

Question 7

Second stage of star cycle

Answer 7

Protostar:
Temp rises as star gets denser
More particles collide
When temp gets high eniugh, hydrogen nuclei undergo nuclear fusion to form helium nuclei
Huge amounts of energy given out which keeps star’s core hot

Question 8

Third stage of star cycle

Answer 8

Main sequence star:
Long stable period ( billions of years )
Outward radiation pressure from nuclear fusion balances inward force of gravity

Question 9

Fourth stage of star cycle

Answer 9

Red giant/ super giant:
Hydrogen begins to run out
Star swells into red giant or red super giant ( if it’s larger )
Becomes reds as surface cools
Fusion of helium occurs and elements up to iron are created in the core of the star

Question 10

White dwarf

Answer 10

Small - medium sized star
Becomes unstable amd ejects outer layer of dust and gas
Leaves behind hot, dense solid core called white dwarf

Question 11

Black dwarf

Answer 11

White dwarf cools
Emits less and less energy
Called black dwarf when it no longer emits a significant amount

Question 12

Supernova

Answer 12

Big stars glow brightly as they undergo more fusion
Contract and expand several times
Evetually theyll explode in a supernova Forms elements more heavy than iron, ejects them into universe to form new stars and planets

Question 13

Neutron star/ black hole

Answer 13

Supernova throws outer layers of dust and gas into space
Leaves very dense core called neutron star
If big enough it will become a black hole: a super dense point in space that not even light can escape from

Question 14

How do satellites maintain their orbit

Answer 14

Gravity provides the force that allows planets and satellites (both natural and artificial) to maintain their circular orbits

Question 15

What is an object moving in a constant circle doing

Answer 15

It’s maintaining speed by changing direction

It’s changing velocity so it must be accelerating

Question 16

Why is their a force acting on an orbiting object and where is it

Answer 16

The object is accelerating so it has to have a force
This force is coming from the centre of the circle
Called centripetal force

Question 17

Why does the object orbiting always travel in a circle

Answer 17

The object keeps accelerating towards what it’s orbiting to

Instantaneous velocity keeps it travelliing in a circle

Question 18

Where is the force acting from to keep the object orbiting

Answer 18

Gravitational force

Between planet and sun or planet and satellite

Question 19

How does the gravitational force change with distance from a planet

Answer 19

As you get closer to a star or planet the stronger the gravitational force is

Question 20

How does the object adjust to remain in orbit with changing distance and gravitational force

Answer 20

The stronger with the force, the faster the orbiting object needs to travel to remain in orbit

Question 21

How does an object remain in a stable orbit

Answer 21

For an object in a stable orbit, if the speed of the object changes, the size ( radius ) of its orbit must do so too.
Faster moving objects will move in a stable orbit with a smaller radius then slower moving ones

Question 22

How do we know that the universe is expanding

Answer 22

Galaxies are moving away from eachother

The wavelength of the light from most distance galaxies has increased

Question 23

Why is the theory called red shift

Answer 23

The wavelengths of the light from different galaxies are all shifted to be longer than normal
Their absorbtion lines on a spectrometer have shifted towards the red end of the spectrum hence the name red shift

Question 24

How does red shift change with distance from the galaxies and what does this suggest

Answer 24

More distant galaxies have greater red shifts than nearer ones which means more distant galaxies are moving away faster than nearer ones

Question 25

What does distant galaxies having greater red shift suggest

Answer 25

It suggests that the whole universe is expanding which prorides evidence for the big bang

Question 26

How did the universe begin

Answer 26

The universe occupied a very small space which was dense and hot. It then started to expand and this expansion is still going

Question 27

What is dark matter and dark energy

Answer 27

Dark matter: unknown substance which holds galaxies together but does not emit any electromagnetic radiation
Dark energy: thought to be responsible for the accelerated expansion of the universe