Unit 8: Astrophysics Flashcards
What is a universe?
Large collection of billions of galaxies
What is a galaxy?
Large collection of billions of stars
Where is our solar system?
In the Milky Way
What are the 8 planets in our solar system (in order from closest to the sun to furthest)?
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
What is the gravitational field strength?
The acceleration an object in the field would epxerience
The gravitational field strength of each planet is…
Different
The gravitational field strength of the moon is … than on Earth.
Less
What causes the orbit of moons, planets, satellites and comets?
Gravitational force
What do moons orbit around?
Planets
What do planets orbit around?
Sun
What do comets orbit around?
Sun
What do satellites orbit around?
Earth
Describe the orbit of comets
Highly elliptical
The closer a comet is to its star, the … it travels
Faster
Describe the orbit of planets
Squashed circles called ellipses
Describe the orbit of moons
Circular orbit
What is orbital radius?
Average distance of the planet to the start it is orbiting
Orbital speed formula
𝑜𝑟𝑏𝑖𝑡 𝑠𝑝𝑒𝑒𝑑 = (2𝜋×𝑜𝑟𝑏𝑖𝑡𝑎𝑙 𝑟𝑎𝑑𝑖𝑢𝑠)/(𝑡𝑖𝑚𝑒 𝑝𝑒𝑟𝑖𝑜𝑑)
What is the time period of a planet?
The planet’s year
What colored stars are the coolest?
Red
What colored stars are the hottest?
Blue
How could different stars be classified?
Stars can be classified according to their colour
Describe the evolution of a star of similar mass to the Sun
Nebula -> main sequence star -> red giant -> white dwarf -> black dwarf
Describe the evolution of a star of a mass larger than the Sun
Nebula -> main sequence star -> red super giant -> super nova -> neutron star/black hole
What are nebula?
Massive clouds of dust and gas, mostly hydrogen
How is the protostar formed?
Gravity pulls the dust and gas together to form protostar
What does fusion in a protostar produce?
A protostar Is not hot enough for fusion to create helium-4 but can create helium-3
What does fusion in a main sequence star produce?
In main sequence stars fusion produces helium-4. Gravity is balanced by pressure and temperature
What happens when the hydrogen has been used?
When all hydrogen has been used helium fusion begins -> red giant or red supergiant
What happens to a main sequence star to transform it into a white dwarf?
When most of the helium has been used the star contracts and emits blue and white light -> a white dwarf
What happens as the white dwarf cools?
As the white dwarf cools it changes into a black dwarf
What happens to Red Supergiants to transform it into a supernova?
Red Supergiants contract unstably and explode throwing dust and gas into space
What happens to the remaining matter from supernova?
Remaining matter from supernova forms very dense core (neutron star)
What happens if the core is more than three times the mass of the sun?
If the core is more than three times the mass of the Sun, it will become a black hole
What is the absolute brightness of a star?
The absolute brightness (or magnitude) is how bright stars would appear if they were all placed the same distance from earth
What is the set distance of absolute brightness?
10 parscecs (32.6 light-years)
What does the Hertzsprung-Russel Diagram show
The luminosity and temperature of different stages of stars
A Hertzsprung-Russell (HR) Diagram
Star classification table and how it can be remembered
Oh Be A Fine Gentleman Kiss Me
Where did all the matter exist before the universe?
All the matter in the universe existed at a single point, called a singularity
What was the density and gravity like in the singularity?
The singularity had infinite density and infinite gravity
What was space and time like before the singularity?
Before the singularity space and time did not exist
What caused the start of space and time?
The Big Bang
After the big bang how do stars and planets form?
Stars and planets form when gravity pulls matter towards each other
Why are stars and planets a certain shape?
Gravity pulls matter to the center and so stars and planets are spherical
What is Cosmic Microwave Background Radiation (CMBR)?
Heat energy left over from the Big Bang
What is the direction of CMBR and frequency?
Low frequency and emitted in all directions
What is CMBR evidence for?
CMBR is evidence for the big bang
What do waves emitted from moving objects show?
Waves emitted from moving objects show change in frequency and wavelength
What happens to observed light wavelength as a star moves further away?
Light wavelength increases
What is the Big Bang Theory?
The theory states that the Universe started at a single point.
The Big Bang theory states that the universe it…
The universe is still expanding
What proves that the universe is still expanding?
All galaxies are moving away from each other
What is red shift?
Wavelength of the light is stretched, so the light is seen as ‘shifted’ towards the red part of the spectrum.
Equation relating change in wavelength, wavelength, velocity of a galaxy and the speed of light
What is the relationship between speed of galaxy moving from Earth and Distance of galaxy away from Earth?
The further away from the Earth, the faster a galaxy is moving
EQ: In 1929, the astronomer Edwin Hubble observed that the light from galaxies moving away from the Earth had longer wavelengths than expected.
What is the name given to this effect? (1)
Red shift.
EQ: The observations made by Hubble support the idea that the Universe is expanding. This means that galaxies are continually moving away from each other and from the Earth. Some dots, which represent galaxies, were marked on a balloon. The balloon was then inflated.
Give one strength and one weakness of this model in representing the idea of an expanding Universe. (2)
Strength: As the balloon expands the dots get further apart, representing the galaxies moving apart.
Weakness: Dots are only on the surface of the balloon, galaxies are throughout the universe
or
there is a limit to how far the balloon can expand, the universe does not
EQ: The ‘Big Bang’ theory uses red-shift as evidence to explain the beginning of the Universe.
How does the red-shift from distant galaxies provide evidence for the beginning of the Universe? (3)
- Red shift shows galaxies are moving away from each other
- More distant galaxies show bigger red-shift/more distant galaxies show a greater increase in wavelength
- More distant galaxies are moving away at faster speed
- Suggests single point of origin of the universe
EQ: What do scientists believe is the origin of CMBR? (1)
The Big Bang
EQ: Why was the discovery of CMBR so important to the scientists believing the Big Bang theory to be correct? (1)
Because CMBR is the left over energy from the Big Bang, and can only be explained by the Big Bang.
EQ: How is the wavelength of CMBR likely to change, if at all, over the next billion years? Give a reason for your answer. (2)
Increase, because the universe continues to accelerate outwards/greater red shift.
