Astrophysics Flashcards
What is the universe
A large collection of billions of galaxies
What is the galaxy
A large collection of billions of stars
what is our sun
juts on of the stars which form the Milky way galaxy
The force due to gravity depends on which two key factors
- mass
- Radius/ distance
what effect does distance and mass have on the gravity
The larger the mass of the body, the stronger it’s gravitational field strength
- The shorter the distnace ( closer you are ) the stronger the gravitational field strength
what does gravitional force d0
- Causes the moon to orbit planets
- causes planets to orbit the sun
- Causes artificial satellites to orbit the earth
- Causes comets to orbit the sun
Explain how gravitational force keeps an object in orbit
- The gravitational force acts towards the body the object is orbiting
-This changes the direction of the velocity
- This means the object is constantly changing direction without changing speed and moves in a curved path around the larger objects.
What are the orbits of the moon and planets usually like
Slightly elliptical
What type of orbit does a comet have
Very elliptical
orbits the sun at one focus
How do you calculate orbital speed
Orbital speed= 2 x PI x orbital radius/ Time period
How do you calculate the distnace of a circular orbit
calculate the circumference
= 2 x pi x orbital radius
what do u measure distnace in
Metres
What are the stages of stella evolution (summarised)
- Nebula
- Protostar
- Main sequence
- Red giant
- white dwarf - Red Super giant
- Supernova
- Neutron star
- Black hole
What is Nebula
- A cloud of dust and gas
How does a star initially start of
from a cloud of stars and gas which is know as neubula
What is a protostar and how is it formed
A protostar is the next stage in the life cycle of a star it follows after nebula
How is it formed?
- Force of gravity pulls together a cloud of dust an gas ( nebula) to form a protostar
How is a star born
hint: formation of protostar
- Temperature rises as stars get denser
- particles have more kinetic energy
- There are more collisions
- When temperatures get high enough hydrogen nuclei under goes nuclear fusion to form helium nucleus
- Gives off huge amounts of energy
- energy given off keeps the core of the star hot
- A star is born
What is the next stage after a protostar is formed?
Main sequence
Describe the main sequence?
A long stable period
- outward pressure caused by thermal expansion balances the force of gravity pulling everything inwards
- this stable period is called main sequence
How long does a star stay in the main sequence
where is the sun now
Several Billions of years
The sun is in the main sequence
What causes outward pressure in the main sequnece
Thermal expansion
this occurs from the huge amount of energy released from nuclear fusion TRYING to expand the star
What comes after the main sequence
Red Giant
Red super Giant
what size is the Red Giant
Same size as the sun
What size is the RED SUPER giant
much bigger than the sun
What is the process of the Red giant
Hydrogen in the core begins to run out
- force due to gravity is larger than the pressure of thermal expansion
Star is compressed until dense and hot enough that the energy created makes the outer layers of the star expand
Why does it turn red after the main sequence
Because the surface cools
If it is a small or large star what will it become after the main sequence
Large- Red SUPER giant
Small- Red giant
What follows after the red giant phase
The star is the same size as the sun
so becomes a white dwarf
Describe the process of becoming a white Dwarf
A small- to medium sized star like the sun
- becomes unstable and ejects it’s outer layer of dust and gas.
- leaving behind a hot dense solid core- white dwarf
What is a white dwarf describe as
Hot, dense solid core
What does a Red SUPER Giant become
Supernova
Describe the process a Supernova
- They expand and contract several times as the balance shifts between gravity and thermal expansion
- eventually explode in a super nova
What is the stage after the Supernova
Neutron star or black hole
Describe the process of the forming of a neutron star
- Exploding supernova throws the outer layers of dust and gas into space
- this leaves a dense core called a neutron star.
What forms a black hole
If the star is massive enough it will collapse and become a black hole
What is a black hole
A super dense point in space that not even light can escape from.
How can stars be classified
by their colours
What does the colour of a star depend on
Visible light it emits
What effects the amount of visible light a star emits of each frequency
Surface temperature
Rank the colour of stars from hot to cold
Hottest
1.Blue
2. White
3.Yellow
4.Orange
5. Red
Coldest
What factors effect the stars Brightness
Size
Temperature
If a star is really hot and big how bright will it be
Very Bright
Finish the sentence
The closer the star …..
The brighter it appears
What do we use Absolute magnitude for
Classifying the brightness of a star
Allows us to compare the brightness of stars without worrying about their relative distances from earth.
Which measurement of absolute magnitude is brighter - Positive or Negative
- Negative measurement is brighter than a positive measurement
What is the location of :
- main sequence
- Red giant/super giant
- White dwarf
on a HR diagram
- Main sequence= Middle
- Red giant/super giant= Top right
- White dwarf= Bottom left
What does a longer wavelength and lower frequency mean
Star is moving way from earth
what is redshift
The light from distance stars
The amount of light from a galaxy
What equation is used to calculate redshift
Change in wavelength/reference wavelength
Velocity of a galaxy / speed of light
What does red shift Suggest
The universe is expanding
What does the expansion of our universe suggest
That something must have got them going
that something causing their initial movement apart is the big bang theory
