Classifying Stars and Red-shift (Paper 2) Flashcards
What is the Hertzsprung-Russell Diagram?
It is a graph showing absolute magnitude against temperature.
What do the groups on the Hertzsprung-Russell Diagram correspond to?
The groups correspond to the different period’s in a star’s life cycle.
Where are the red giants and the super red giants on the Hertzsprung-Russell Diagram? And why?
In the top-right corner.
This is because they are very cool but very large so very bright.
Where are the white dwarfs found on the Hertzsprung-Russell Diagram? And why?
White dwarfs are found in the bottom left. This is because they are very hot but small so are dim.
Where are the main sequence stars found on the Hertzsprung-Russell Diagram? And why?
They span the whole range of the graph diagonally from top left to right bottom. This is because all the main sequence stars are rounghly the same size. The brighter the star, the higher the temperature.
Where is the Sun found on the Hertzsprung-Russell Diagram?
Draw a basic Hertzsprung diagram. Remember the axes are back to front!!
y-axes decreases as it goes up. x-axes decreases as you go along it.
What does a stars brightness depend on?
It’s size and temperature. In general, the bigger and hotter the star, the brighter it is.
What does the brightness stars appear from Earth depend on?
The distance to Earth. The closer the star, the brighter it appears.
Why don’t we only measure the brightness of a star?
If we just looked at brightness, we may end up classifying stars that are very far away but very bright in the same group as a star that is relatively dim, but nearby, which wouldn’t be very useful.
What formula do you need to calculate red-shift?
The amount by which light from a galaxy is red-shifted is determined by the following formula.
How can you calculate the velocities of galaxies?
Knowing how much light from galaxies is red-shifted.
