In the early 20th century, astronomers Henry Russell and Ejnar Hertzsprung constructed a diagram called the Hertzsprung-Russell diagram (HR diagram) that compares the luminosity and surface temperature of stars. The HR diagram serves as an important tool for astronomers to classify stars and reveal relationships between stars by showing them at different ages and stages of evolution. It classifies stars into groups based on their surface temperatures from hottest, blue-white group O stars to coolest, red group M stars.

1. Classification of
Stars

2. TEKS 8.8A describe
components of the universe
including stars, nebulae and
galaxies, and use models
such as the Herztsprung-
Russell diagram for
classification
TEKS 8.8B recognize that the
Sun is a medium-sized star
near the edge of a disc-
shaped galaxy of stars and
that the Sun is many
thousands of times closer to
the Earth than any other star

3. In the early twentieth
century, astronomers
Henry Russell and Ejnar
Hertzsprung
Hertzsprung
Russell
constructed a
diagram
comparing
two
properties of
stars.

4. This graph, called the
Hertzsprung-Russell Diagram
(HR Diagram)
became one of astronomers’
most important tools.

5. Think of
the HR
Diagram
as a sort
of family
portrait of
the stars.

6. It shows
stars at
different
ages and
stages of
their
evolution.

7. The HR
diagram
serves as a
tool to reveal
the
relationships
and
differences
among stars.

8. The HR Diagram
compares the
luminosity and surface
temperature of stars.

9. Luminosity is the
total amount of
energy that the star
radiates or simply
put; the brightness of
the star.

10. The surface
temperature
of a star is
determined
directly by
observing
the star’s
color and
the spectral
patterns.

11. Astronomers
classify stars into
stellar groups
based on their
surface
temperatures.

12. The groups are O, B,
A, F, G, K and M.
Group O stars are the
blue-white and
hottest, while group
M stars are red and
coolest.

13. Copy and answer in journal
1. This is called the “family portrait” of the stars
_________________________.
2.It shows stars at different _________ and
_________ of their evolution.
3.The HR diagram compares _______________ and
___________________ of stars.
4.Luminosity is the total amount of _________ that a
star radiates, which is the ________________ of a
star.
5.Surface temperatures is determined directly
observing the star’s __________ and
________________________.
6.Blue star’s are ______________ while red star’s are
_________________.
7.Astronomers classify stars into groups by their
______________________________.

15. • Star A--- 5500 C/K Luminosity Low
• Star B--- 2500 C/K Luminosity Low-Med
• Star C--- 3350 C/K Luminosity High
• Star D--- 25000 C/K Luminosity High Med
• Star E--- 26000 C/K Luminosity 1 sun
• Star F--- 11000 C/K Luminosity 104
sun
• Star G--- 9000 C/K Luminosity 10 -2
• Star H--- 22500 C/K Luminosity 10 -4
• Star I---2850 C/K Luminosity Medium
• Star J--- 15000 C/K Luminosity 10 -1
• Challenge Plot a star of your choice-Use ED

17. Assignment
In your TEXTBOOK
Complete your test review-this will count as
your quiz grade
Page 337-340