Download Stars Study Guide KEY

Stars Study Guide KEY
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Use this KEY to check your study guide for accuracy. Answers do not need to be word-forword the same…but important facts/details should not be missing!
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Objective: 8. Diagram the life cycle of a star.
1. What role does gravity play in the birth of a star?
Gravity pulls the gas and dust in a nebula together. A star is born when the contracting gas
and dust become so hot that nuclear fusion starts
2. How is the mass of a star related to how long the star will live?
How long the star lasts depends upon how massive it is. The more mass a star has, the faster
it burns out. High mass stars die faster; low mass stars live longer lives.
3. Describe the life cycle of a low/medium mass star. (Tell the steps in the life cycle.)
The steps in a low/medium mass star’s life are: nebula, mature star, red giant, planetary
nebula, white dwarf, black dwarf.
4. Describe the life cycle of a high mass star. (Tell the steps in the life cycle.)
The steps in a high mass star’s life are: nebula, mature star, red SUPER giant, then
supernova. After that, it can become a nebula again or become either a neutron star or a black
hole.
5. Describe a “mature star”. (What is happening at its core? What is it “giving off”?)
Nuclear fusion is happening in the core of a mature star. It is giving off light and heat.
6. Tell how low mass stars are similar to high mass stars.
All stars begin in a nebula, are made of matter, burn due to nuclear fusion, and will eventually
die. Once they begin to run out of fuel, they all go through “giant” phases.
7. Tell how low mass stars are different from high mass stars.
Low mass stars will not go “supernova” and don’t become black holes or neutron stars. They
do not burn with a white or blue color. They have less gravity. Low mass stars can become
white/black dwarves; high mass stars will not.
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, ITR Sheet Objective 9: Describe how scientists use light to analyze stars.
Objective 10: Describe our sun in terms of age, temperature,
size, color, and chemical composition
8. How do scientists use a star’s spectrum to find out what it is made of?
They analyze the star’s black line spectrum to see what stars are made of. They use the
pattern of lines to figure out what elements are present in the star. (They can do this because
each element has its own pattern of lines.)
9. What are most stars made of? Hydrogen, helium, and a small amount of other elements
10. What is “apparent magnitude” and what does it depend on?
It is how bright a star appears to our eyes as seen here on Earth. It depends on how far away
the star is and how bright the star actually is (it’s absolute magnitude)
11. What is “absolute magnitude” and what does it depend on?
It is how bright the star actually is (compared to our sun or other stars). It depends on the star’s
size/mass and temperature.
12. Why do stars with more mass tend to be brighter than low mass stars?
High mass stars have more self-gravity which causes them to burn at a higher temperature
and to appear brighter.
13. How do white dwarfs and neutron stars compare in size to our Sun?
They are both smaller than our Sun. White dwarfs are “planet size” objects; neutron stars are
only about 20 km in diameter.
14. Describe what a low-mass star’s temperature and color range would be.
Low mass stars have less self-gravity which means they burn at lower temperatures and
produce yellow-orange-red colors.
15. Describe what a high-mass star’s temperature and color range would be.
High mass stars have more self-gravity which causes them to burn at a higher temperature
and to produce white-blue colors.
16. Describe our sun’s chemical composition, size, color, and temperature.
Composition = mostly hydrogen and helium; Size = medium; Color = yellow or yellow-orange;
Temperature = ~ 5500°C;
Objective 12: Define and differentiate the types of galaxies.
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Objective 13: Describe the Big Bang Theory and the evidence used to
support the theory.
17. Describe the “Big Bang Theory”.
Originally, the universe was tiny, hot, and dense. (Everything was compressed together into a
small ball.) Then, an enormous explosion threw matter in all directions. (The matter eventually
formed everything that we now see.)
18. What evidence is used to support the theory? (Tell two)
Galaxies are still moving outward from the explosion (and away from each other). Cosmic
background radiation has been discovered- it is supposed to be heat left over from the
explosion.
19. Describe how galaxies are moving in the universe at this time.
Galaxies are moving away from each other. They are speeding up as they move away.
20. How old is the universe? About 13.7 billion years
21. How old is our solar system? About 5 billion years old
22. Describe the two theories about what will happen with the universe in the future.
One possibility is that gravity will pull the universe together to form an enormous black hole.
Another possibility is that the universe will expand forever.