
The H-R Diagram is actually a graph that
illustrates the relationship that exists between
the average surface temperature of stars and
their absolute magnitude, which is how bright
they would appear to be if they were all the
same distance away.

Rather than speak for the brightness of stars,
the term “luminosity” is often used. Luminosity
is a measure of how much energy leaves a star
in a certain period of time. Generally, for stars
that are at equal distances from the Earth, the
more luminous a star, the brighter it is.

The luminosity of stars is not only affected by
temperature but also by size. The most
luminous stars would be those that are large
and hot. Those that are least luminous would
be small and cool. The color of a star is
determined by its surface temperature, which is
illustrated on the H-R Diagram.
Back page!

Using the H-R Diagram provided with
this activity, answer the following
questions.

What is the variable on the x axis?

What is the variable on the y axis?

What is the approximate surface temperature of the sun?

Would the surface temperature of the stars classified as white
dwarfs be generally higher or lower than that of stars classified as
super giants?

What is the color of the stars shown on the diagram that have the
highest surface temperature?

What is the color of the stars shown on the diagram that have the
lowest surface temperature?

List the colors of the stars from the color of the hottest
star to the color of the coldest star.

How many groups of stars are located on the H-R Diagram?
White dwarfs, main sequence, super giants, and giants.

Most of the stars shown on the diagram are classified as which
type of star?
White dwarfs, main sequence, super giants, or giants?

Our sun is classified as which type of star?

Name a star that is very dim and red in color.

Where are the brightest stars found on this diagram?

Where are the dimmest stars found on this diagram?

Where are the coolest stars found on this diagram?

Where are the hottest stars found on this diagram?

Where will we find the hottest and brightest stars?

Where will we find the coolest and brightest stars?

Where will we find the coolest and dimmest stars?
Sun
Sirius
Luminosity
Color
Surface
Temperature

Compare and contrast our sun to Sirius in terms
of luminosity, color, and surface temperature.