Astrophysics Flashcards
Define a universe
Contains everything that there is
Created by the big bang 13.7 billion years ago
expanding faster than the speed of light
Define galaxy
10 to the power of 11 in our universe
Collection of billions of stars
We are in the Milky way
Define stars
Made of hydrogen
Nuclear fusion of H to He
Define Solar systems
Everything that orbits our sun is part of our solar system
What are satellites
Anything that orbit a planet
How do satellites orbit
Orbit in circles around planets
How do planets orbit
Slightly elliptical around stars
How do comets orbit
Highly elliptical around stars they speed up when closer due to the gravitational force
Give the weight mass gravity equation
w = m x g
Every object has a ……………..field around it. The field strength is………for larger masses.
Gravitational
Larger
What is weight measured in
N
What is the orbital speed equation
v = 2πr ÷ T
Orbital speeds are usually measured in….
Km/s
Stars have different……….. , …………and………….
Colours, sizes and brightnesses
What are stars grouped by
Their colours
What colour will a hot and cold star be
Hot = Blue
Cold = Red
Describe the birth of a star
Nebula = a cloud of gas and dust. It compresses due to gravitational forces that attract all the particles together
Fusion begins = The nebula heats up and pressure increases and starts to glow. This heats up further, eventually at 10 million kelvin, fusion begins
Main sequence stars = when the star becomes stable it’s called a main sequence star
Radiation pressure = gravitational force
H fuses to He
Solar System = Unused material around the star is grouped together to form planets, comets, etc.
Describe the life of a star
Nebula collapses due to gravity
It heats up and fusion begins
Pressure increases
Main sequence star = stable
Eventually hydrogen runs out, star compresses because gravitational force is greater than radiation pressure. temperature + pressure increase, fusion of helium begins. The star swells to a massive size. The surface is cooler so it appears red.
Eventually helium runs out. Gravitational force dominates again, compressing the star and heating it up but not enough to fuse Carbon. It now glows white and is called a white dwarth. They are millions of times denser than anything on Earth
As the c
dead star cools, the colour changes to black
Describe the life of a big star
Nebula collapses due to gravity
Heats up,pressure increases and fusion begins
Main sequence star stable due to radiation pressure = gravitational force
When hydrogen runs out the star fuses all the elements up to iron. It swells to an ENORMOUS size called a super Red Giant
When fuel finally runs out it collapses and explodes = Super Nova
The core that remains is EXTREMELY dense!!
Neutron star
If the star was massive the core would be even denser, gravity cannot escape = black hole
What two things does the brightness of a star depend on
Luminosity (power output)
Distance from Earth
The brightness of a star is called it’s…………………..
Apparent magnitude
What is Absolute Magnitude
Compares all the stars as if they would appear at a set distance from Earth
Describe the birth of the universe
All the matter and all the energy in the universe started from a suer small, hot, dense point called a singularity that suddenly exploded about 13.8 billion years agoIt has been expanding ever since
What is the doppler effect
if the source of a wave is moving towards us, then the wavelength is compressed. for light waves this is called blue shift. If the source is moving away then the wavelength is stretched and called red shift. This can happen with sound
What si the equation for the doppler effect
λ - λ
—————– = v/c
λ 0
What is C
Speed of light
3x10 to the power of 8
The faster something moves the greater the…………
Red shift
