•
•
•
•
•
Properties of Stars
Apparent Magnitude: the ____________________________ of a star as it
_________________________ from Earth.
– ___________________________
– ___________________________
– ___________________________
Absolute Magnitude: how bright the star ______________________ is.
– Two stars with the same apparent magnitude may not have the same
absolute magnitude.
– Two stars with different apparent magnitude may have different absolute
magnitude.
Color and Temperature
– Stars with the highest temperatures appear _________ (53,500oF).
– Stars with middle temperatures appear __________ (8,500-10,300oF).
– The coolest stars appear ______________.
• Hertzsprung-Russell Diagram: shows the relationship
between the ________________________
magnitude and the
____________________________________ of
the stars.
– Temperature is also related to size: the
______________________ the size of the
star, the _______________________ the
temperatures.
• Binary Stars: pairs of stars that orbit each other.
– These stars are used to determine the stars’
masses.
– The stars move in a circle around a center of _______________.
• If the center of mass is directly in the _______________ between the 2 stars,
the masses are the same.
• If the center of mass is ________________ to one of the stars, then that star
is ________________.
Variable Stars: stars that fluctuate in brightness.
– Cepheid variable star: brightness ____________________________ at a regular
interval called a light period. (Bright  dim  bright, etc.)
– Nova: ______________________ brightening of a star usually due to a nova
eruption.
• The brightest moment is seen within a few days, remains bright for a few weeks,
then returns to normal brightness within a year.
_______________________ (interstellar matter): clouds of dust and gases.
– If this matter gets too close to a hot star, it will ____________________.
– This is known as a bright nebulae.
– There are two types of bright nebulae.
• _______________________ Nebulae: turns energy into _____________________________ which
fluoresces.
• _______________________ Nebulae: dense ______________________ of dust reflect the
_____________________ from nearby stars
(Nova)
(Nebula)
(Nebula)
(Horsehead Nebula)
How are stars born?
 Galaxies are clouds of _______________ and _____________ called
___________________
 hydrogen gas in the nebula becomes clumped together by
___________________
 cloud begins to _____________
 over ______________________ of years, more hydrogen atoms are
pulled into the spinning cloud
 _____________________________ between hydrogen atoms become
more frequent  hydrogen gases __________________________.
 Temperatures above 15,000,000oC  ____________________ increases
and ____________________________ (the combining of 2 atoms into 1)
 2 ______________________ atoms  _________________ atom
 Great ___________ and ___________________ is given off  a new star
(protostar)
What is the life cycle of a star?
 _____________________  nuclear fusion
 Eventually, the star will run out of hydrogen
 The ____________________ core ___________________ and ______________ up
 The outer shell is still composed mainly of _______________________
 Heating of the helium  outer shell to ____________________ greatly.
 As it expands  _______________ and turns into a _________________________
Depending on the mass of the star, 1 of 2 things can happen to the
red giant.
 ____________ mass stars turn into
_______________________________
 It shines bright ____________________________ before it
turns into a dead star (this will be the fate of our sun).
 ____________ mass stars turn into a _________________ , then
break apart in an explosion called a
_______________________________________
 ___________________ of a supernova serve as a ______________________ place for stars.
 a ___________________________ can form
What is a black hole?
 After a supernova explosion, the core remains so __________________________, that it
________________________ into an object smaller than a neutron star.
 The _________________________ of the core is so strong that _____________________ can’t
________________________ the surface
 Swallows _____________________ and ________________________ as if it were a vacuum cleaner.
Assignment
• Hertzsprung Russell Diagram Worksheet
• Life Cycle of Stars Foldables (page 710 in textbook)
The Hertzsprung-Russell Diagram
The Hertzsprung-Russell 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 of 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 Earth, the more
luminous a star, the brighter it is.
The luminosity of stars is affected not only by temperature but also by size. The most luminous stars would be those that
are large and hot. Those that are the least luminous would be small and cool. The color of a star is determined by its surface
temperature, which is illustrated on the Hertzsprung-Russell diagram.
Using the Hertzsprung-Russell diagram provided in this activity, answer the following questions.
1. What is the approximate surface temperature of the sun? _________________
2.
Would the surface temperature of the stars classified as white dwarfs be generally higher or lower than that of stars
classified as supergiants? _____________________
3.
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 start to the color of the coldest star.
Color of the hottest star _______________________________
_______________________________
_______________________________
_______________________________
Color of the coldest star _______________________________
4.
Most of the stars shown on the diagram are classified as which type of star? _____________________
5.
Our sun is classified as which type of star? __________________________
6.
How is it possible for white dwarfs to have a lower luminosity than the sun even though the sun is much cooler than
the white dwarf? __________________________________________________________________________
_______________________________________________________________________________________
Instructions for Life Cycles of Stars Foldables
Fold
here
Fold
here
1. Low Mass Stars
a. Take a piece of plain paper and turn it to the landscape position.
b. Fold in both ends until they meet in the middle.
c. Divide the outer flaps into 6 sections by drawing 3 lines as shown on the diagram below.
d. In sections 1-5, draw a picture of each low mass star stage. Leave section 6 blank.
e. On the inside flaps, write a description of each stage in the same area as the drawing.
f. In the middle section on the inside of the foldable, draw a cartoon that includes characteristics of
the different life stages of low mass stars.
Steps a and b
1
4
1
2
5
2
3
Do not
use
Front Side (Steps c and d)
4
Cartoon using
star
characteristics
5
3
Inside (Steps e and f)
2. Medium Mass Stars
a. Follow the steps written above except use 8 sections (instead of 6) and leaves section #8 blank.
3. Massive Stars
a. Follow the steps written for low mass stars except use 8 sections (instead of 6) and leave section #8
blank.
b. Label the “neutron star” as section #6A and the “black hole” as section #6B.