Space - paper 2 Flashcards
To revise space (Paper 2)
Describe our solar system
the Sun, plus the eight planets and the dwarf planets that orbit around the Sun. Natural satellites, the moons that orbit planets, are also part of the solar system.
State the name of our galaxy
The milky way
How was the sun formed
The Sun was formed from a cloud of dust and gas (nebula) pulled together by gravitational attraction. This cloud heats up until fusion can start.
What reaction takes places in all stars
Nuclear fusion
Why are stars stable?
Fusion reactions lead to an equilibrium between the gravitational collapse of a star and the expansion of a star due to fusion energy.
Describe the life cycle of a small star, like the sun
- Nebula or Protostar
- Main sequence star
- Red Giant
- White dwarf
- Back dwarf
Describe the life cycle of a large star
- Nebula or Protostar
- Main sequence star
- Red Super Giant
- Supernova
- Neutron star or Black hole
How is a red giant formed?
Hydrogen runs out and the star initially collapses as gravity is now the stronger force. After a star collapses, the star heats up enough for helium to fuse and it expands (radiation pressure > gravity)
What type of star is the sun?
A main sequence star
How is a white dwarf formed?
The red giant starts to run out of its fuel (Helium) Gravity is greater than radiation pressure so the star collapses
Which was the first element created by the big bang
Hydrogen nuclei (protons)
How were the light elements made
Fusion in stars
How were the heavy elements made
Fusion in supernovas
How were all the elements distributed through the universe
By supernovas
What forces keeps planets in orbit around a star
Gravity
What is a stable orbit?
A stable orbit is one in which the satellite’s speed is just right - it will not fly off into space (too fast) or spiral into the Earth (too slow) but will travel around a fixed path.
What is the relationship between orbit radius and speed.
The gravitational attraction between two objects decreases with distance. This means that the closer the two objects are to each other, the stronger the force of gravity between them. This means that objects in small orbits travel faster than objects in large orbits. In order to change orbital speed, an object must change the radius of its orbit at the same time, to maintain a stable orbit.
Define the doppler effect
The change in frequency of a wave, caused by relative motion between the source of the wave and the observer
Why is the pitch higher when a car is moving towards you?
Wavelength is decreased so frequency is increased
Why is the pitch higher when a car is moving away from you?
Wavelength increases so frequency has decreased
Define red shift
There is an observed increase in the wavelength and decrease in frequency of light from distant galaxies.
What is the relationship between the distance a galaxy is from Earth and thier speed?
The further away the galaxies, the faster they are moving and the bigger the observed increase in wavelength.
Define Blue shift
A decrease in wavelength and an increase in freqency as a glaxaxy moves towards an observer.
What evidence does red shift provide?
The observed red-shift provides evidence that space itself (the universe) is expanding which supports the Big Bang theory.
What is the big bang theory
The Big Bang theory suggests that the universe began from a very small region that was extremely hot and dense.
Describe the universe before the big bang
Hot and dense
How can an object in orbit be travelling at a constant speed but still be accelerating
The object is constantly changing direction, so the velocity must be changing A change in velocity is an acceleration .
The object is always accelerating towards the centre of the orbit
How many stars are in our solar system?
One - the sun
What are natural satellites?
The moons that orbit planets
What are the properties of dark matter?
- It has mass
- It cant be directly observed as it does not emit or absort em radiation
- It is only effected by gravity
- There is lots of it
How do we know dark matter exists?
It can bend (refract) light
Why do we think there is dark energy?
THe rate of expansion of the universe is accelerting
