P8.3 Flashcards
What is red shift
When something is moving away from you the wavelength of the light that it emits increases and the frequency decreases. This is called red shift.
What happens if the source is moving quicker
The red shift is bigger
What happens if the source is moving towards you
It is blue shifted
What is the big bang model
The movement of galaxies provides evidence for an expanding universe. They believe that it started from something extremely dense and smaller than an atom which expanded suddenly 13.7 billion years ago. It is the space between galaxies that is expanding
Other evidence for the Big Bang model
In the 1960s scientists discovered there was microwave radiation coming from all directions. It was the radiation left over from the big bang, this is cosmic microwave radiation. The high energy and frequency has been stretched over time so it is now the microwave region of the electromagnetic spectrum.
What is the sun
The star at the centre of the solar system
What are planets
Objects that are spherical because of gravity, in orbit around the sun.
What are moons
Objects in orbits around planets
What is minor planets
Anything that is not a planet or a comet in orbit around the Sun, including asteroids and dwarf planets such as Pluto
What are comets
Objects made of ice and dust in orbit around the sun
What are the four inner planets
Mercury, Venus, Earth and Mars.
What characterises the inner planets
They are all rocky and have an atmosphere
What are the four outer planets
Jupiter, Saturn, Uranus and Neptune
What are Jupiter and Saturn
They are gas giants. They all have rings and lots of moons.
What are Neptune and Uranus
Ice giants. They all have rings and lots of moons
What is between Mars and Jupiter + what is it
Between Mars and Jupiter is an asteroid belt. Asteroids are piece of rock left over from the formation of the solar system
What state is our star in
They are in equilibrium state and are called main sequence stars.
Where does the gas and dust come from
It comes from other stars that have reached the end of their lifeline.
What are the moons around planets called
They are called natural satellites
What are artificial satellites
Artificial satellites are satellites sent out by humans.
What is a geostationary orbit
Time for one orbit - 24 hours
Height above earths surface - about 36000km
Features - remains in a fixed position above the earth’s equator
Uses - communications and satellite television
What is a polar orbit
Time for one orbit - 2 hours
Height above earths surface - up to 2000km
Features - orbits over the poles
Uses - military (spying), observation of the earth, weather
Why are orbits circular
The gravitational force that acts on any object in orbit is always towards the centre of the planet. This is at right angles to the velocity, The force changes the direction of the motion so it is accelerating even though its speed doesn’t change.
What do all objects emit
Electromagnetic radiation
What does the type of electromagnetic radiation emitted depend on
It depends on the temperature of the object
What does a hotter object mean
It means it emits more radiation of a higher frequency and shorter wavelength and less radiation of a lower frequency and longer wavelength.
What does the graph for a hot star and a cold star peak over
It peaks over a higher frequency towards the blue end of the spectrum. The cold star peaks over tge red end of the spectrum
What is the intensity of radiation at each frequency for hot stars compared to cold stars
The intensity of the radiation at each frequency is higher for a hot star than a cold star.
When something is at a constant temperature what does this mean
It means that it absorbs the same amount of radiation as it’s emitting.
How does the earth’s atmosphere affect the temperature of the earth
The earth’s atmosphere reflects some of the radiation back to the earth. The type and intensity of the radiation depends on the concentration of greenhouse gases in the atmosphere.
What happens to the electromagnetic radiation from the sun
The earth receives some electromagnetic radiation from the sun some of the electromagnetic radiation is absorbed by the atmosphere and some is reflected.
What does the earth’s surface do
It radiates infrared back into space because it’s warmed by the sun. Some of the Earth’s infrared is radiated back towards the earth’s surface by the atmosphere
What is inside the earth
The earth has a solid inner core, an outer core which is liquid, a mantle which is solid but can flow and the crust is solid.
What do earthquakes produce and what can we do with the products
Earthquakes produce seismic waves and scientists use seismometers to detect them
What does a seismogram do
It measures the arrival and intensity of two types of seismic waves.
P-waves : primary waves
S-waves : secondary waves
What are P-waves and what can they travel through
P-waves are longitudinal waves, so they can travel through solids and liquids.
What are S-waves and what can they travel through
S-waves are transverse waves and can’t travel through liquids
where can you detect p-waves and s-waves
You can detect p-waves and s-waves all over the world however, there are regions called shadow zones where you can’t detect p-waves or s-waves.
Because of the shadow regions
The core of the earth must be a liquid
What is the universe made up of
A collection of billions of stars
What holds a galaxy together
gravity
What is an orbit
The curved path of a celestial object around another object
What happens when the size of the orbit decreases
Gravitational force increases and speed also increases in order to maintain a stable orbit
What is the first stage of the formation of the sun
It starts with a big cloud of dust and gas called a nebula
What is the second stage of the formation of the sun
The gravity pulls the dust and gas together forming a protostar. As more particles join the protostar it gets bigger and its gravity stronger. This allows it to attract more dust and gas. The gravity makes the protostar more dense leading to an increased number of collisions and a greater temperature.
What is the third stage of the formation of the sun
When the protostar gets hots enough the hydrogen nuclei fuse together to form a helium nuclei in nuclear fusion. This gives out lots of energy keeping the core hot.
When the core is hot what is the star called
A main sequence star
When it’s a main sequence star what happens
The outward pressure caused by the release of energy by nuclear fusion is the same as the inward pressure due to gravity.
What is the fourth stage of the life cycle of the star
The star runs out of hydrogen causing nuclear fusion to stop and the inward pressure of gravity to compress the star into a small ball until its hot and dense enough for fusion to start up again and it to expand. This forms heavier elements up to iron.
What is the fifth stage of the life cycle of the star
When a small/medium star expands it forms a red giant
When a big star expands it forms a red super giant
What happens to the red giant 1
It becomes unstable and expels its outer layers. Leaving behind a hot dense solid core called a white dwarf.
What happens to the red giant 2
The white dwarf gets cooler and dark and becomes a black dwarf as it no longer has enough energy to emit light.
What happens to the red supergiant 1
After several cycles of expansion and contraction a supernova occurs and forms elements heavier than iron.
What happens to the red supergiant 2
Massive stars form a black whole
Less massive stars form a neutron star
