P16 Flashcards
What is our solar system made up of
The sun 8 planets Dwarf planets e.g Pluto Moons Artificial satellites e.g ISS
What are moons
Natural satellites that orbit planet
What are the 8 planets in order from the sun
Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune
What is our solar system a part of
Itβs part of the milky way galaxy
A collection of billions of stars held together by gravity
What is the simple life cycle of a star
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 )
First stage of star cycle
Cloud of dust and gas called nebula
Force of gravity pulls them together to form protostar
Second stage of star cycle
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 starβs core hot
Third stage of star cycle
Main sequence star:
Long stable period ( billions of years )
Outward radiation pressure from nuclear fusion balances inward force of gravity
Fourth stage of star cycle
Red giant/ super giant:
Hydrogen begins to run out
Star swells into red giant or red super giant ( if itβs larger )
Becomes reds as surface cools
Fusion of helium occurs and elements up to iron are created in the core of the star
White dwarf
Small - medium sized star
Becomes unstable amd ejects outer layer of dust and gas
Leaves behind hot, dense solid core called white dwarf
Black dwarf
White dwarf cools
Emits less and less energy
Called black dwarf when it no longer emits a significant amount
Supernova
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
Neutron star/ black hole
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
How do satellites maintain their orbit
Gravity provides the force that allows planets and satellites (both natural and artificial) to maintain their circular orbits
What is an object moving in a constant circle doing
Itβs maintaining speed by changing direction
Itβs changing velocity so it must be accelerating
Why is their a force acting on an orbiting object and where is it
The object is accelerating so it has to have a force
This force is coming from the centre of the circle
Called centripetal force
Why does the object orbiting always travel in a circle
The object keeps accelerating towards what itβs orbiting to
Instantaneous velocity keeps it travelliing in a circle
Where is the force acting from to keep the object orbiting
Gravitational force
Between planet and sun or planet and satellite
How does the gravitational force change with distance from a planet
As you get closer to a star or planet the stronger the gravitational force is
How does the object adjust to remain in orbit with changing distance and gravitational force
The οΏΌstronger with the force, the faster the orbiting object needs to travel to remain in orbitοΏΌ
How does an object remain in a stable orbit
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
How do we know that the universe is expanding
Galaxies are moving away from eachother
The wavelength of the light from most distance galaxies has increased
Why is the theory called red shift
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
How does red shift change with distance from the galaxies and what does this suggest
More distant galaxies have greater red shifts than nearer ones which means more distant galaxies are moving away faster than nearer ones
What does distant galaxies having greater red shift suggest
It suggests that the whole universe is expanding which prorides evidence for the big bang
How did the universe begin
The universe occupied a very small space which was dense and hot. It then started to expand and this expansion is still going
What is dark matter and dark energy
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
