Name: __________________________________
Star in a Box
First, read this…!
Have you ever wondered what happens to the stars in the night sky as they get older? The Star in a Box
application lets you explore the life cycle of stars. It animates stars with different starting masses as they
change during their lives. Some stars live fast-paced, dramatic lives; others change very little for billions
of years. This app visualizes the changes in mass, size, brightness and temperature for all these different
stages.
Access the Star in a Box app at: https://starinabox.lco.global/. Choose Normal and then Open the lid.
The graph is a Hertzsprung-Russell (HR) diagram, where a star’s luminosity is plotted against its
temperature. The information panels allow you to compare the Sun with your star. It compares the relative
radius, surface temperature, brightness (luminosity) and mass of the star to the Sun.
A. The Sun’s Evolution
The star you will view is the same size as our sun. Click the start button and watch what happens.
Describe the changes in the size, color and stage of star during the simulation. You can change the data
you are looking at by clicking on the different icons at the bottom of the information section. You will
want to run the simulation several times to observe all of the differences.
1. Name the three stages of the sun’s life shown on the HR diagram.
 Stage 1:
 Stage 2:
 Stage 3:
2. Click on the Data Table tab in the upper right. Complete Table 1.
Stage
Radius
(Compared to
the Sun)
Brightness
(Compared to
the Sun)
Temperature
(Kelvin)
Duration (million
years)
Table 1: Data for a star that is same size as our Sun
3. Use Table 1 to complete the following statements with increases, decreases, or stays the same.
a. From Stage 1 to Stage 2, the star’s radius_________________. From Stage 2 to Stage 3,
the star’s radius _________________.
b. From Stage 1 to Stage 2, the star’s luminosity (brightness)_________________. From
Stage 2 to Stage 3, the star’s luminosity _________________.
c. From Stage 1 to Stage 2, the star’s temperature _________________. From Stage 2 to
Stage 3, the star’s temperature _________________.
4. Rank the star stages in order of increasing duration (time star spends in each stage).
_________________ => _________________ => _________________
5. Open the Lid. Move the cursor over the HR diagram. You should see red lines that allow you to
read temperature and brightness values at any point on the diagram.
a. What is the maximum temperature that the Sun will reach? __________ Kelvin
b. How many times brighter than it is now will the Sun be at its maximum temperature?
__________
c. During its final stage, our Sun will have relatively __________ (low/high) temperature
and __________ (low/high) brightness.
B. Evolution of other Stars
Follow the evolution of stars of different starting masses by choosing from the menu in the lower left of
the app. Complete Table 2, filling in a row for each of the different masses. (Hint: You may find it easier
to use the Data Table to find the exact values, but be sure to also watch the HR diagram that depicts each
star’s evolution.)
Mass of
Star (Msun)
Maximum
Radius
(Compared
to the Sun)
Maximum
Brightness
(Compared to the
Sun)
Maximum
Temperature
(Kelvin)
Name of Final
Stage
0.2
1
6
10
30
Table 2: Data for stars of varying masses
Questions:
1. Where on the main sequence do the lower mass stars start?
2. Where on the main sequence do the higher mass stars start?
Total
Lifespan
(millions of
years)
Does the star
become a
supernova?
3. There are three possible outcomes for the final stage of a star’s life depending on its initial mass.
What are these final stages?



4. Refer to the data in Table 2:
a. Which mass star reaches the highest temperature? _______________At what stage in its
life does the star reach this temperature? _______________
b. Which mass star gets the most luminous (brightest)? _______________ Is this the same
mass of star that reaches the highest temperature? _______________
The following questions are multiple choice.
5. What type of star will the Sun become after it leaves the Main Sequence?
Neutron Star | Red Dwarf | Red Giant | Red Supergiant
6. What main factor determines the stages a star will follow after the main sequence?
Mass | Luminosity | Temperature | Radius
7. The mass of the star Betelgeuse is much greater than the mass of the Sun; therefore, its total
lifetime will be:
Greater than the Sun | The same as the Sun | Less than the Sun
8. Compared to when it joins the Main Sequence, a star’s mass at the end of its life will:
Be greater | Be the same | Be less | Depends on the type of star
9. The Sun will spend most of its life in what stage?
Main Sequence | Red Giant | Red Dwarf | White Dwarf
"Star in a Box: Advanced, 2013" by E. Gomez, AstroEdu is licensed under CC BY-NC 4.0 / A derivative from
the original work