5. [4pt] Choose the correct statements concerning spectral classes of stars. (Gi
ID: 3309122 • Letter: 5
Question
5. [4pt]
Choose the correct statements concerning spectral classes of stars. (Give ALL correct answers, i.e., B, AC, BCD...)
A) The spectral types of stars arise primarily as a result of differences in chemical composition.
B) Oh Be A Fine Guy/Girl Kiss Me, is a mnemonic for remembering spectral classes.
C) Neutral hydrogen lines dominate the spectrum for stars with temperatures around 10,000 K because a lot of the hydrogen is in the n=2 level.
D) The spectral sequence has recently been expanded to include L, T, and Y classes.
E) Hydrogen lines are weak in type O-stars because most of it is completely ionized.
F) K-stars are dominated by lines from ionized helium because they are so hot.
Answer: Last Answer: ABCDE
Not yet correct, tries 1/5
Hint: In O stars, the hydrogen lines are weak because much of the hydrogen is ionized. A-type stars (photosphere temperature around 10,000 K) show strong hydrogen lines because a lot of the hydrogen is in the n=2 level.
6. [4pt]
Choose the correct statements concerning the electromagnetic spectrum given off by stars. (Give ALL correct answers, i.e., B, AC, BCD...)
A) All stars are the same color as our Sun.
B) A hot star will be more red in color than a cooler star.
C) Blue photons are less energetic than red photons.
D) If we see a blue star and a red star in a nearby star cluster, we know the blue star is hotter.
E) Blue photons (blue light) have a longer wavelength than red photons.
F) Hot stars are much brighter than cool stars of the same size and distance from the Earth.
Answer: Last Answer: F
Incorrect, tries 1/5.
Hint: As the temperature of an object increases two things happen; more higher energy photons are emitted (Wien's Law) and the total number of photons increases (Stefan's Law).
7. [4pt]
Match each characteristic below of a one-solar-mass star to its appropriate phase. Answer M for Main-sequence Star, or P for Protostar.
If the first is M and the rest P, enter
MPPPPPP).
A) radius much larger than the Sun
B) pressure and gravity are NOT precisely balanced.
C) lasts about 10 billion years
D) energy generated by nuclear fusion
E) surface radiates energy at same rate that core generates energy
F) luminosity much greater than the Sun
G) energy generated by gravitational contraction
Explanation / Answer
Solution (5)- Correct statements are BCDE.
Statement A and Statement F are incorrect.
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