Hertzsprung-Russell Diagrams
- Stars are classified using the Hertzsprung-Russell (HR) diagram
- This is a plot of:
- The luminosity on the y-axis
- This is from dim (at the bottom) to bright (at the top)
- The temperature on the x-axis
- This is from hot (on the left) to cool (to the right)
- This is normally in Kelvin
- The luminosity on the y-axis
The Hertzsprung-Russell Diagram
- The main features of the Hertzsprung-Russell diagram are:
- Most stars lie on the Main Sequence. This is the band of stars going from top left to bottom right
- Below the main sequence (and slightly to the left) are the White Dwarfs
- Above the main sequence on the right-hand side are the Red Giants
- Above those are the Red Supergiants
- This means the white dwarfs are dimmer and hotter than the red giants which are brighter and cooler
- Sometimes, the absolute magnitude is on the y-axis instead
- Remember this will still go from dimmest (highest number) at the bottom to brightest (lowest number) at the top!
Exam Tip
Make sure you remember the key components of this diagram to be able to draw this diagram from memory, more specifically which way around the axis go - the x-axis is the opposite way round to what you might be used to!