How should we expect the Milky Way's interstellar medium to change in 50 billion years?

The interstellar medium (ISM) of the Milky Way comprises gas and dust, playing a crucial role in the processes of star formation. Over a time span of 50 billion years, we can anticipate significant changes in this medium primarily due to the lifecycle of stars and the dynamics of galactic processes.

As stars form from the ISM, they eventually evolve and end their lives, often shedding their outer layers back into the ISM via stellar winds or supernova explosions. Over an extended period, especially as the Milky Way ages, star formation rates will decline. Young, massive stars contribute to the active and dynamic nature of the ISM, but as these stars exhaust their gas supplies and as newer generations of stars take longer to form, the total gaseous content will start to decrease.

Furthermore, gravitational interactions with other galaxies or the eventual merging of nearby dwarf galaxies could alter how gas is distributed or incorporated into the Milky Way. However, as the galaxy ages, the combination of reduced star formation and the extended lifecycle of the remaining gas will lead to a situation where the total amount of gas within the Milky Way is significantly reduced compared to today.

Given these processes and the expected future evolution of the galaxy, the assessment that the total amount