HR Diagram
Characteristics of Stars
Temperature/Color
Mass
Luminosity
• Absolute Magnitude
• Apparent Magnitude
The Spectral Sequence
O
B
Hottest
50,000K
Bluest
A
F
G
K
M
L
Coolest
1300K
Reddest
Oh Boy, an F grade kills me, Louis!
The mass of a star
determines the
length of its life
cycle (how long
will it burn).
Sun-like Stars
Up to 1.5 times the mass of the Sun
Huge Star
From 1.5 to 3 times the mass of the Sun
Giant Star
Over 3 times the mass of the Sun
Sun/main
sequence
star
Stellar
Nebula
Red
Giant
Planetary
Nebula
Protostar
(nursery)
Massive Star
( Huge & Giant)
Neutron
Star
Red
Supergiant
Supernova
Black
Hole
White
Dwarf
Variables which affect
a star’s brightness:
Star size
Distance from
Earth
Star temperature
Absolute
Magnitude
vs.
• Actual Brightness:
How large and hot
a star is in relation
to other stars.
Apparent
Magnitude
• Apparent
Brightness: The
amount of light
received on Earth
from a star.
Which star looks like
it is giving off more
light?
•But, which star is actually giving off more light?
Luminous/Brighter
Stars
Dim Stars
Hotter
Stars
Cooler
Stars
O
B
A
F
G
K
M
• Life Cycle of Stars Interactive Investigation
http://aspire.cosmic-ray.org/labs/star_life/starlife_main.html
• HR Diagram Interacative Lab
http://aspire.cosmic-ray.org/labs/star_life/hr_interactive.html
• Stellar Evolution/H-R Diagram Simulation
http://instruct1.cit.cornell.edu/courses/astro101/java/evolve/evolve.htm
• Astronomy Place Tutorials
http://media.pearsoncmg.com/bc/bc_bennett_cosmicpers_2/medialib/tutorials/inde
x.html