Download What are most stars made of

Stars, Galaxies, and Constellations: Study Guide KEY
Check your answers against the KEY. Answers do not need to be exactly the same, but key
ideas must match and important information should not be missing in your answers.
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.
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.
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. 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.
6. 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.
Objective 9: Describe how scientists use light to analyze stars.
Objective 10: Describe our sun’s age, temperature, size, color, and composition
7. 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.)
8. What are most stars made of?
Hydrogen, helium, and a small amount of other elements
9. What does a star’s brightness depend on?
It depends on the star’s mass (size) and temperature.
10. 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.
11. How are a star’s size (mass), temperature and color related?
High mass stars have more self-gravity which causes them to burn at a higher temperature
and to produce white-blue colors. Low mass stars have less self-gravity which means they
burn at lower temperatures and produce yellow-orange-red colors.
12. 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.
13. Identify and describe the three main types of galaxies.
Spiral = central disk with arms that spiral outward, can be “bar” or “pinwheel”;
Ellipse = round/flattened ball of stars;
Irregular = does not fit the other two patterns; does not have a regular shape.
14. Tell what type of galaxy the Milky Way is.
Scientists think it’s a spiral; it is probably a bar spiral, but may be a pinwheel.
Objective 13: Describe the Big Bang Theory and the evidence used to support it.
15. 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.)
16. 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.
17. 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.
18. How old is the universe?
About 13.7 billion years
19. How old is our solar system? About 5 billion years old
20. 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.
Name: _________________________________
Period : _______
Stars, Galaxies, and Constellations: Study Guide, page 3
Page: 114/115
Objective 11. Describe the stories associated with five major
constellations; draw each constellation accurately.
21. Draw five constellations using the correct number of stars and correct placement. Tell the
“nickname: of each constellation.
Orion
Nickname: ______________
Scorpius
Nickname: ______________
Cassiopeia
Nickname: ______________
Cygnus
Nickname: ______________
Ursa Major
Nickname: ______________