Download Life Cycle of Stars

Stars
What is a star?
• A star is a ball of plasma held
together by its own gravity
– Nuclear reactions occur in stars (H 
He)
– Energy from the nuclear reactions is
released as electromagnetic radiation
Characteristics of Stars
• DISTANCE
– Measured in light-years
• The distance which a ray of light would
travel in one year
• About 6,000,000,000,000 (6 trillion) miles
per year
• 186,000 miles per second
Life Cycle of Stars
http://hea-www.cfa.harvard.edu/CHAMP/EDUCATION/PUBLIC/ICONS/life_cycles.jpg
Life Cycle of Stars
1. Begin their lives as clouds of dust and gas
called nebulae
Gravity may cause the nebula to contract
Matter in the gas cloud will begin to condense
into a dense region called a protostar
The protostar continues to condense, it heats
up. Eventually, it reaches a critical mass and
nuclear fusion begins.
2. Here begins the main sequence phase of the
star. Most of its life is in this phase
Main Sequence Stars
• A major grouping of stars that forms a
narrow band from the upper left to the
lower right when plotted according to
luminosity and surface temperature on the
Hertzsprung-Russell diagram
Life Cycle of Stars
Life span of a star depends on its size.
3. Very large, massive stars burn their fuel
much faster than smaller stars
4. Their main sequence may last only a few
hundred thousand years
5. Smaller stars will live on for billions of years
because they burn their fuel much more
slowly
6. Eventually, the star's fuel will begin to run
out.
Life Cycle of Stars
7. It will expand into what is known as a red
giant
8. Massive stars will become red
supergiants
9. This phase will last until the star
exhausts its remaining fuel
10. At this point the star will collapse
Life Cycle of Stars
11. Most average stars will blow away their
outer atmospheres to form a white
dwarf
12. Their cores will remain behind and burn
as a white dwarf until they cool down
13. What will be left is a dark ball of matter
known as a black dwarf
Life Cycle of Stars
14. If the star is massive enough, the
collapse will trigger a violent explosion
known as a supernova
15. If the remaining mass of the star is about
1.4 times that of our Sun, the core is
unable to support itself and it will
collapse further to become a neutron
star
Life Cycle of Stars
16. The matter inside the star will be
compressed so tightly that its atoms are
compacted into a dense shell of
neutrons. If the remaining mass of the
star is more than about three times that
of the Sun, it will collapse so completely
that it will literally disappear from the
universe. What is left behind is an
intense region of gravity called a black
hole
Life Cycle of Stars
http://www.seasky.org/cosmic/sky7a01.html
9. Scientists classify stars according to: _______,
SIZE
_______, & ________
Temperature
Brightness
Temperature
10. A star’s color reveals its __________. The
RED while the hottest
coolest stars glow ______,
BLUE
stars glow ___________.
Types of Stars
Classification
Class
Temperature
Color
O
20,000- 60,000 K
Blue
B
10,000 – 30,000 K
Blue-white
A
7,500 – 10,000 K
White
F
6,000 – 7,500 K
Yellow-white
G
5,000 – 6,000 K
Yellow
K
3,500 – 5,000 K
Orange
M
2,000 – 3,500 K
Red
Q: Based on its color, is our sun very
NO
hot? ___________
11. Brightness
___________ of a star depends on its
Temperature
___________
and __________.
SIZE
Brightness can be measured in terms of
luminosity
magnitude
_____________or
in______________.
Luminosity
12. __________
is how much
power the star
gives off as
compared to our
Sun. Our sun’s
luminosity is 1.
Magnitude
13. _____________
is the measure of
light stars
generate from their
surface. An
incredibly bright
star has a
magnitude of -5 or
more, an average
star’s magnitude is
close to 1, and a
dim star’s
magnitude is
around 10.
• 14. Each star is born, goes
through its life cycle, then
DIES
___________.
http://www.answers.com/topic/stellar-classification