question of the day question: describe the doppler effect. answer: ……… turn in: -p. 534 cyu...
TRANSCRIPT
Question of the DayQuestion of the DayQuestion of the DayQuestion of the Day
Question: Describe the Doppler Effect.
Answer: … … …
Turn In:-p. 534 CYU #3-7, 9-Expansion of Space
Turn In:-p. 534 CYU #3-7, 9-Expansion of Space
Cars and Stars
Size For cars: curb weight For stars: intrinsic brightness
Energy Produced For cars: horsepower For stars: temperature/ color
How long it takes to burn all its fuel For cars: mileage- how long it takes to burn 1 tank
of gas For stars: hydrogen gas
ECity Mileage vs Weight
0
5
10
15
20
25
30
35
40
45
50
0 1000 2000 3000 4000 5000 6000 7000
Curb Weight
Cit
y M
ilea
ge
Series1
INVERSE RELATIONSHIP
Horsepower vs Curb Weight
0
100
200
300
400
500
600
0 1000 2000 3000 4000 5000 6000 7000
Curb Weight
Ho
rsep
ow
er
Series1
DIRECT RELATIONSHIP
2500 5000 10000 20000 40000
Temperature (K)
What type of relationship is this?
Direct
Which car graph is this most similar to?
Horsepower vs Curb Weight
Stellar Evolution
Stars exist because of gravity. Mass attracts mass.
A nebula (cloud of gas and dust) provides the starting material.
Stellar Evolution
As the cloud is squeezed, the temperature rises, it ignites and a star is born.
A star is a ball of gases balanced between gravity’s contraction (pulling in) and nuclear explosions (pushing out).
Nuclear Explosions
Protostar
Gravity continues to cause contraction of star
Core is heated more than the surface
Nuclear fusion begins
Huge amounts of energy are released
Main Sequence Star
Balanced between gravity’s contraction and gas pressure’s expansion
Massive stars burn fast (several million yrs.)
Small stars burn slow (hundreds of billions)
Average stars burn for about 10 billion yrs. The sun is an average sized star
90% of a star’s life is spent as Main Seq.
2500 5000 10000 20000 40000
Temperature (K)
Why do we call them “Main Sequence Stars?”
Most of the stars fall on the “best-fit line” on this graph, which we call the main sequence
• same graph you just saw, but with one change (look at the x-axis)
• x-axis goes from largest to smallest
• Traditional way that the H-R Diagram is displayed
• Draw and label the main sequence in your notes
H-R Diagram
Red Giant (old age)
All hydrogen fuel has been used
Core contracts and heats up
Heat causes star to expand up to 1000 times larger
Star cools as it expands
Fate of average mass stars
Supergiant (old age)
Fate of large mass stars
Core contracts and heats up
Heat causes star to expand
Star cools as it expands
Generates all the elements on the periodic table (up to iron)
Burnout and DeathSmall and Average StarsSmall stars: Main Sequence White Dwarf Black Dwarf
Medium stars:Main Sequence Red Giant White Dwarf
Black Dwarf
Supernovas
Supernovae are one of the most energetic explosions in nature, making them like a 1028 megaton bomb (i.e., a few octillion nuclear warheads).
These two photographs are of the same part of the sky.
This photo was taken in 1987 during the supernova explosion of SN 1987A.
This photo was taken before the Supernova explosion
After a Supernova, the core of the star…
Neutron Star: very small and very dense
Black Holes: gravity is so large that even light cannot escape