# The hr diagram shows relationship between what two factors

### Stars and the Hertzsprung-Russell Diagram Teacher Sheet - Science NetLinks What are the four important things to note about the HR Diagram? Part Two. Describe the general trend between temperature and luminosity that the Main Sequence shows. Science NetLinks is a project of the Directorate for Education and Human Resources Programs of the American Association for the Advancement. In an H-R diagram the luminosity or energy output of a star is plotted on the vertical axis. Just to confuse things, the lower or more negative the magnitude, the that is simply the difference in the magnitude of a star when measured through two Most stars seem to fall into group A. It shows a general trend from cool, dim. A plot of the nearest stars on the HR diagram is shown below: cool faster (emit energy faster) than small objects, so there must be some correlation with radius.

Stars and the Hertzsprung-Russell Diagram Teacher Sheet Introduction These are some suggested answers for the questions asked on the student sheet. Luminosity and temperature Describe why it is possible to relate the temperature of a star to its luminosity, or brightness. Stars that are hotter should be brighter than stars that are cooler.

Why is measuring the luminosity of stars difficult? The distance of stars relative to earth makes it difficult to measure brightness since a bright star that is more distant might appear to be as bright as a more dim star closer to earth.

What star serves as a standard of comparison against which the luminosity of other stars is measured? Sketch and label the HR Diagram. Make sure to label the axes, the main sequence, white dwarves, giants, and super giants. Students should sketch the HR Diagram, from the website: The class of star that corresponds to the color we observe from earth.

What are the four important things to note about the HR Diagram? In either case, the scale is a "ratio scale" in which stars are compared to each other based upon a reference our sun. Usually this is labeled using the Kelvin temperature scale. In most graphs and diagrams, zero or the smaller numbers exist to the left on the diagram. This is not the case here.

On this diagram, the higher hotter temperatures are on the left, and the lower cooler temperatures are on the right. Some HR diagrams include the color of stars as they can be seen through filters on spectrophotometers.

This is also a "ratio scale. A star in the upper left corner of the diagram would be hot and bright. A star in the upper right corner of the diagram would be cool and bright.

### The Hertzsprung-Russell diagram shows the relationship between what two factors

The Sun rests approximately in the middle of the diagram, and it is the star which we use for comparison. A star in the lower left corner of the diagram would be hot and dim. A star in the lower right corner of the diagram would be cold and dim. Click the diagram below, we have five stars. How would you describe the temperature of Star A? And the faint, hot stars are called white dwarfs.

• Stars and the Hertzsprung-Russell Diagram Teacher Sheet
• Hertzsprung–Russell diagram
• Classifying Stars - the Hertzsprung-Russell Diagram

The spectral classification types were more accurate then attempts to measure the temperature of a star by its color. This had the advantage of being more linear than temperature nicely spaces letters and contained more information about the star than just its temperature the state of its atoms.

HR Diagram Explained

The HR diagram becomes a calculating tool when one realizes that temperature, luminosity and size radius are all related by Stefan-Boltzmann's law.

The standard Stefan-Boltzmann law is for point sources, an idealized case. Real objects have size, which means surface area. Large objects cool faster emit energy faster than small objects, so there must be some correlation with radius.

## The Hertzsprung-Russell diagram

For stars, the luminosity, temperature and radius are linked by an expansion of Stefan-Boltzmann's law that says: Knowing from laboratory measurements that Stefan-Boltzmann's constant is 5. For example, the Sun is 6. Therefore, its luminosity is 3. On a log-log plot, the R squared term in the above equations is a straight line on an HR diagram. This means that on a HR diagram, a star's size is easy to read off once its luminosity and color are known.

### Classifying Stars - The Hertzsprung -Russell Diagram

The HR diagram is a key tool in tracing the evolution of stars. Stars begin their life on the main sequence, but then evolve off into red giant phase and supergiant phase before dying as white dwarfs or some more violent endpoint. Energy generation is the heart of stars. It provides the energy that we see as light, and it also supplies the heat and pressure that supports a stars' structure.

The power source for stars is thermonuclear fusion. Normally, particles with like charges positive-positive or negative-negative repel each other, this is called electrostatic repulsion.

The primary output from a thermonuclear reactions are photons in the form of gamma-rays, but a large number of other particles are produced as well. The simplest fusion reaction is the proton-proton chain, common in all main sequence stars. 