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General Concepts

• Why are astronomers interested in studying the space between stars?
• What are we referring to when we talk about the interstellar matter/medium?
• What are the two most common elements in interstellar space?
• Roughly what percentage of the interstellar gas is hydrogen? Helium?
• On average, how much matter is there in interstellar space?
• What is the dust in interstellar space made of?
• Do atoms in interstellar matter combine to form molecules?

Effects

• Does red or blue light pass more easily through dust in space?
• What effect does gas in interstellar clouds have on starlight?
• What effect does dust in interstellar clouds have on starlight?
• What is the difference between the effects of interstellar gas and dust?

Nebulae

• What is a nebula?
• Why are most emission nebulae red?
• Why are most reflection nebulae blue?
• What are Messier objects?
• Do reflection and emission nebulae look different?
• Why are certain nebulae dark?
• How can we detect the presence of a dark nebula?
• Do dark nebulas emit anything?
• Why are some of the darker, denser nebulae called molecular clouds?
• What is the Crab Nebula?
• What is the Eagle Nebula?
• What is the Horsehead nebula?

21-cm Radation

• Where does 21-cm radiation come from?
• Why is 21-cm radiation important?
• What kind of telescope would you use to detect 21-cm radiation?