Over time, what is the net effect of the star-gas-star cycle in the Milky Way?
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.

Question

Quizplus · Accepted Answer

The star-gas-star cycle involves the formation of new stars from the interstellar medium (gas and dust), which is then enriched in heavy elements by supernova explosions. However, as more stars form and go through their lifecycles, they eventually end up as white dwarfs or neutron stars, which do not contribute gas back into the interstellar medium. As a result, over time, the total mass in the galaxy's interstellar medium is gradually reduced, even though the remaining gas is enriched in heavy elements.

Over Time, What Is the Net Effect of the Star-Gas-Star