L4
讲座
1. What does the professor main discuss?
ways that stars become nebulae
reasons that nebulae appear to give off blue light
difference between nebulae and stars
a basis for classifying types of nebulae
2. What point does the professor make about Orion’s sword?
It contains two stars that are remnants of a supernova.
It points toward a nebula in the constellation taurus.
It contains a nebula that looks like a star to the naked eye.
It contain stars whose light is a reflection of other nearby stars.
3. What does the professor say about the origin of the crab nebula?
It was formed when interstellar gas clouds combined.
It was created by an exploding star.
It did not emit when it was first formed.
It was formed in the same way as many reflection nebulae.
4. Based on the lecture, which answer choices describe emission nebulae and which describe reflection nebulae?
They give off red light.
They give off blue light.
They can only be seen from locations near the equator.
They do not contain glowing gas.
5. What is a typical characteristic of dark nebulae?
They are too hot to emit radiation in the visible range.
They are obscured from view by nearby stars.
They are located in parts of the sky that do not contain bright stars.
The dust and gas they contain are too dense to let light through.
6. Why does the professor say this:
To clarify his previous statement
To call attention to an unusual phenomenon
To emphasize a feature of all types of nebulae
To repeat a point he made earlier
