5.2 Hertzsprung-Russell Diagram Flashcards
In the Hertzsprung-Russell diagram, how does the temperature scale run?
From high to low so the hottest blue and blue-white stars are on the left hand side and the cooler red stars are to the right.
What does the luminosity scale use as a reference?
The Sun, so a star with a luminosity of 100 emits 100 times the power of the Sun.
What is the initial process in the formation of a star?
The gravitational attraction of the interstellar hydrogen nuclei.
The loss of potential energy leads to an increase in the gas temperature.
The gas becomes denser and when the temperature is high enough the nuclear fusion process begins.
This creates helium nuclei and, as the temperature rises, these can also fuse, liberating even more energy.
This is what is happening in the main sequence.
The luminous stars in the main sequence last for only a short time (perhaps a million years) whereas the Sun’s life is expected to be about 10 billion years.
What is on the Y and X axis of the diagram?
Y- relative luminosity
X- surface temperature
How is a protostar formed?
Gravitational energy is converted into heat energy, so the temperature rises.
When the temperature is high enough, hydrogen nuclei undergo nuclear fusion to form helium nuclei and give out massive amounts of heat and light.
What does the process of nuclear fusion involve?
Joining hydrogen nuclei together, to make helium nuclei.
This process involves the release of huge amounts of energy.
Describe fully what will happen in the Sun that will make it change from a main sequence star into a red giant.
Hydrogen used up Helium fuses Expands Causing cooling If the original star had sufficient mass, a red supergiant is formed.
