Transcript Stars and H-R Diagram

Characteristics of Stars
Temperature/Color
Mass
Luminosity
• Absolute Magnitude
• Apparent Magnitude
The mass of a star
determines the
length of its life
cycle (how long
will it burn).
Sun
(main sequence
star)
•Longest period
of a star’s life
Stellar
Nebul
a
(nursery
)
Protost
ar
White
Dwarf
Red
•Nuclear
Giant decreases
•Core contracts
•Outer layers
expand
Massive Star
( Huge)
•Longest period
of a star’s life
Red
Supergiant
Planetary
•Outer
layers drift
Nebula
to outer space
•Outer layers lost
to nebula
•Nuclear decreases
•Core contracts
•Outer layers expand
Superno
•Core
vacollapses
instantly
•Massive shortlived explosion
•Outer layers
blown away
•Shrinks
•Few thousand
miles in diameter
•No nuclear
reactions
Neutro
n Star
•Shrinks to
small
dense star
•Very
strong
gravity
Black
Massive Star
(Giant)
Red
Supernov
•Very strong gravit
Hole
that light can’t
escape
Two Kinds of Brightness
Apparent Magnitude: How
bright the object appears to
us on Earth.
Absolute Magnitude: How
bright a star actually is.
Which star appears brighter to the
observer?
Star B
2L
L
Star A
d
2d
Which star looks like
it is giving off more
light?
•But, which star is actually giving off more light?
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
Properties of Stars
•
•
•
•
•
Mass – The single most important property that
determines other properties of the star.
Luminosity – The total amount of energy (light)
that a star emits into space.
Temperature – surface temperature, closely
related to the luminosity and color of the star.
Spectral type – closely related to the surface
temperature
Size – together with temperature determine the
luminosity
What can we measure directly?
The Easy Ones:
• Apparent brightness: a well-calibrated
detector.
• Temperature: spectroscopy
• Spectral type: spectroscopy