PLEASE HELP THIS IS MY LAST CHEGG QUESTION! SORRY ABOUT THE AMOUNT OF QUESTIONS

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PLEASE HELP THIS IS MY LAST CHEGG QUESTION! SORRY ABOUT THE AMOUNT OF QUESTIONS I NEED AN ASTRONOMY EXPERT

5. 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.

6. 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.

7. 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

8. Suppose you gathered a ball of interstellar gas that was equal to the size of the Earth (a radius of about 6400km). If this gas has a density of 1.9 hydrogen atoms per cm3, typical of the interstellar medium, what would its total mass be? The volume of a sphere is 4/3 * * R3. (For comparison, a bowling ball has a mass of about 5 kg)

9. At the average density of of a star-forming molecular cloud, about 880 atoms per cm3, determine how large a sphere you would need to encompass mass equal to that of the Sun? Enter the radius of this sphere in light-years.

Explanation / Answer

5. A - Correct statement

B - Correct statement

C - correct statement

D - Correct tatement

E - Correct statement

F - wrong Statement

6. A - Wrong

B - Wrong

C - Wrong

D - Wrong

E - Wrong

F - Correct

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