P16(Space) Flashcards
How did the sun form
Formed at the centre of a spinning cloud of dust,gas and rock due to the force of gravity
What is a protostar
A concentration of gas and dust that becomes hot enough to cause nuclear fusion
How does a star form
-When a protostar temperature increases and it gets hotter
-therefore the process of nuclear fusion can take place
-therefore energy is released in the fusion of hydrogen nuclei into helium nuclei
-causing the protostar to get hotter and brighter
-therefore causing a star to be born
How is energy released inside a star
Hydrogen nuclei fuse together to form helium nuclei
How is a star stable
-Energy released in the core makes the fusion process continue
-Therefore radiation such as gamma radiation flows out from the core in all directions
-The force of gravity acts inwards making the star contract
-The radiation from nuclear fusion in its core acts outwards making the star expand
When do stars become unstable
When stars have no more hydrogen nuclei in their cores that can fuse together
What is the lifecycle of a star with a similar mass to our sun
Protostar—> main sequence —> red giant —> white dwarf —> black dwarf
What is the lifecycle of a star with a greater mass than our sun
Protostar —> main sequence star —> red supergiant —> supernova —> black hole or neutron star
What is a red giant
Stars with a similar mass to our sun swell out and cool down and turn red
What is a white dwarf
Hot dense white star much smaller in diameter than it was before
What is a black dwarf
When white dwarfs fade out and go cold
What is a red supergiant
Stars much bigger than the sun swell out and collapse
What is a supernova
The explosion of a red supergiant after it collapses
What is a neutron star
An extremely dense object made up of only neutrons
How do neutron stars form
The supernova compresses the core of the star into a neutron star
What is a black hole
An extremely dense object where the gravitational field strength is so strong that nothing can escape from it
How do black holes form
The supernova compresses the core of the star into an extremely dense object
How does a planet stay in its orbit
The force of gravity between a planet and its host star keeps the planet moving along its orbit
How are circular orbits formed
-Objects in circular orbit are travelling at a constant speed
-The orbit is a circular path
-therefore the direction in which the object is travelling will be constantly changing direction
-A change in direction causes a change in velocity
-Acceleration is the rate of change of velocity
-therefore if the object is constantly changing direction then its velocity is constantly changing
-so the object in orbit is accelerating
-A resultant force is needed to cause an acceleration
-This resultant force is gravity and it must act at right angles to the instantaneous velocity of the object to create a circular orbit
-This is always towards the centre of the orbit
Planet’s furthest from the sun …
Take the longest amount of time to orbit the sun because they travel at the slowest speeds
Planet’s closest to the sun …
Take the shortest amount of time to orbit the sun because they travel at the fastest speeds
A satellite needs to travel at a specific speed to …
maintain a circular orbit at a particular distance from the object
If the speed of the satellite is too big …
-The radius of the orbit will increase and the satellite will spiral into space
-This is because the gravitational attraction cannot provide enough force to keep it in orbit
If the speed of the satellite is too small …
-The radius of the orbit will decrease and the satellite will move towards the object it should -be orbiting
This is because the gravitational attraction is too strong to maintain a constant orbital radius
If an artificial satellite is to change the radius at which it is orbiting then the …
speed at which it is travelling must change
To maintain a stable orbit:
If the speed increases…
the radius must increase
To maintain a stable orbit:
If the speed decreases…
the radius must decrease
What is the Doppler effect
-The wavelength of the waves in front of the source decreases and the frequency increases
-The wavelength behind the source increases and the frequency decreases
What is blueshift
If an object moves towards an observer the wavelength of light decreases
What is red shift
If an object moves away from an observer the wavelength of light increases
The further away a distant galaxy is …
The greater it’s red shift
What did Edwin Hubble discover
-The light from distant galaxies was red shifted
-Therefore distant galaxies are moving away from earth
-Therefore the universe is expanding
The greater the distance a galaxy is from Earth…
The greater the speed at which it is moving away from Earth
What is the Big Bang theory
-Around 14 billion years ago, the universe began from a very small region that was extremely hot and dense
-Then there were a series of explosions, which we call the Big Bang
-This caused the universe to expand, cooling as it does so, to form the universe we currently observe
What is CMBR(cosmic microwave background radiation)
Electromagnetic radiation that was created just after the Big Bang
What is dark matter
-Evidence from the rotation and motion of galaxies suggests that there is much more matter in the Universe than we are able to account for
-This unseen matter is given the name dark matter and its nature is not currently known
What is dark energy
-Measurements of the expansion of the Universe using supernovae suggest that the Universe is starting to expand at a faster rate
-It has been suggested that this accelerated motion is caused by dark energy pushing everything in the Universe apart
If the density of the universe is less than a particular amount it will ….
-Expand forever
-causing the stars to die out
-therefore causing everything else to die
If the density of the universe is more than a particular amount it will …
-Stop expanding and go into reverse
-All matter will then clump together into a single dense point
What is the evidence for the Big Bang theory
The red shifts of distant galaxies
