How should we expect the Milky Way's interstellar medium to be different in 50 billion years than it is today?
A)The total amount of gas will be much less than it is today.
B)The total amount of gas will be much greater, since many stars will undergo supernovae between now and then.
C)Thanks to the recycling of the star- gas- star cycle, the interstellar medium should look about the same in 50 billion years as it does today.
D)The total amount of gas will be about the same, but the percentage of elements heavier than hydrogen and helium will have risen from the current 2% to more than 50%.

Question

Quizplus · Accepted Answer

In 50 billion years, the total amount of gas in the Milky Way's interstellar medium is expected to be much less than it is today because many of the gas clouds will have been converted into stars, and the rate of star formation will decrease as the available gas is used up. Additionally, not all the material from dying stars returns to the interstellar medium; some of it is permanently locked away in white dwarfs, neutron stars, and black holes.

How Should We Expect the Milky Way's Interstellar Medium to Be