Over the course of tens of billions of years, what is the result of the star-gas
ID: 298012 • Letter: O
Question
Over the course of tens of billions of years, what is the result of the star-gas-star cycle in a typical spiral galaxy?
A.The total mass in the galaxy's interstellar medium is gradually increased, and the new gas is continually enriched in heavy elements.
B.The total mass in the galaxy's interstellar medium is gradually reduced, and the remaining gas is continually enriched in heavy elements.
C.The temperature of the interstellar medium varies between the cool 10-50 degrees (Kelvin) required to form stars and the 2000-30,000 degree (Kelvin) temperatures of the outer layers of the stars that form. But over time, more and more of the interstellar medium remains cool.
D.The gas of the interstellar medium is continually depleted in elements heavier than helium.
E.There is no net effect to the cycle. Mass in the interstellar medium lost to star formation is exactly replaced by stellar winds and supernova explosions.
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Recall that novae refer to the periodic brightening of white dwarfs. Which of the following is not true about novae?
A.A star system that undergoes a nova may have another nova sometime in the future.
B.When a star system undergoes a nova, it brightens considerably, but not as much as a star system undergoing a supernova.
C.A nova involves fusion taking place on the surface of a white dwarf.
D.Our Sun will probably undergo at least one nova when it becomes a white dwarf about 5 billion years from now.
E.The word nova means "new star" and originally referred to stars that suddenly appeared in the sky, then disappeared again after a few weeks or months.
Explanation / Answer
Over the course of tens of billions of years, what is the result of the star-gas-star cycle in a typical spiral galaxy?
Answer is
B.The total mass in the galaxy's interstellar medium is gradually reduced, and the remaining gas is continually enriched in heavy elements.
Explanation:
With passage of time mass is reduced.and the remaining gas will become rich in heavy elememnts.
Recall that novae refer to the periodic brightening of white dwarfs. Which of the following is not true about novae?
Answer is D
Our Sun will probably undergo at least one nova when it becomes a white dwarf about 5 billion years from now.
Explanation:
When it becomes a white dwarf about 5 billion years from now Sun will go through nova.
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