Space Physics Flashcards
How do stars initially form? (1)
From a cloud of dust and gas called a nebula.
What is the second part of a star formation called when a protostar is formed.
The force of gravity pulls dust and gas together to form ma protostar.
The temperature rises as star gets denser and more particles collide with each other.
When temperature gets high enough hydrogen nuclei undergo nuclear fusion to form helium nuclei.
Gives out huge amounts of energy which keeps core of star hot.
A star is born.
What is the third part of star fomation when it becomes a main sequence star?
Star enters long stable period
Outwards pressure caused by nuclear fusion that tries to expand the star balances the force of gravity pulling everything inwards.
In this stable period it is called main sequence star and typically lasts 7 billion years.
Sun is in middle of this stable period
What is the fourth part of star formation when it becomes white dwarf?
A small to medium size star like sun then becomes unstable and ejects its outer layer of dust and gas.
Leaves behind hot dense solid core called a white dwarf.
What is fifth part of star formation when it becomes a black dwarf?
As white dwarf cools down emits less and less energy
When it no longer emits a significant amount it is called a black dwarf
Describe sixth part of a star when supernova is formed.
Big stars glow brightly as they undergo more fusion and expand and contract several times.
Form elements as heavy as iron in various nuclear reactions.
Eventually they explode into supernova forming element heavier than iron and ejecting them into universe to form new planets and stars.
Stars and all life cycle produce and distribute all naturally occuring elements
Describe the last stage of star life cycle when it becomes a black hole.
Exploding supernova throws outer layers of dust and gas into space leaving a very dense core called a neutron star.
If star is big enough it becomes a black hole a super dense point in space that not even light can escape from.
What are planets?
large objects that orbit a star.
8 in our solar system
have to be large enough to have ‘cleared their neighbourhoods’ this means gravity is strong enough to pulled in any near objects apart from natural satellites
What are dwarf planets?
pluto
planet like objects
orbit stars
don’t meet all rules to be a planet
What is a moon
orbit planets
type of natural satellite
not man made
What are artificial satellites?
satellites that humans have built
Orbit the Earth
What is milky way galaxy?
Collection of billions of stars that are held together by gravity.
If an object is constantly moving in circles what is it doing?
Changing direction, so it is constantly accelerating.
And constantly changing direction.
For an object to accelerate what does it need?
A force acting on it
Force directed towards centre of circle
What does force do to an object?
Fall towards whatever it is orbiting but as object is already moving it just causes it to change direction.
What does an object keep accelerating towards?
What it orbits.
But instantaneous velocity keeps it travelling in a circle
Force that makes it happen is gravitational force between planet and sun or between planet and satellite
What happens the closer you get to a star or planet?
Stronger gravitational force is.
Stronger force, faster orbiting object needs to travel to remain in orbit
For an object in a stable orbit what happens to speed of object?
It changes, and radius of orbit changes too.
Faster moving objects wil move in stable orbit with a smaller radius than slower moving ones.
Evidence galaxies seem to be moving away from each other.
- when we look at light from most distant galaxies wavelength has increased
- wavelengths are longer than they should be so shifted towards red end of spectrum - this is red shift.
What does red shift suggest?
source of light moves away from us
Measurement of red shift indicate that these distant galaxies are moving away from us quickly.
Same result whichever direction you look in.
What has greater red shift?
Distant galaxies than nearer ones. So more distant galaxies are moving away faster than nearer ones.
How do balloons relate to the expansion of the universe and how galaxies are moving further away?
1= balloon covered in pompoms 2= as you blow into balloon it stretches 3= Pompoms move away from each other 4= Balloon represents universe and each pompom is a galaxy 5= as time goes on space stretches and expands, moving galaxies further from each other 6= Shows how expansion of space makes it look like galaxies move from us
Describe big bang theory
All matter in universe occupied a very small space
tiny space was dense so very hot too
Then it exploded and space started to expand and expansion still goes on.
Problem with big bang theory
Lots we dont know about universe
Observation of supernovae from 1998 to present day show distant galaxies move away from us faster and faster
What do scientists curently think of the universe?
Made up of dark matter and dark energy
What is dark matter?
unknown substance which holds galaxies together.
Doesn’t emit EM radiation
What is dark energy?
Responsible for accelerated expansion of universe
Problem with all of these theories?
But no one knows what these things are so lots of theories about it these theories get tested over time and either get accepted or rejected.
