The Galaxy can be schematized as a disk of radius \(15 \mathrm{kpc}\) and thickness \(200 \mathrm{pc}\). Since we know that \(1 \mathrm{pc}=3.08 \times 10^{16} \mathrm{~m}\), determine the volume of the Galaxy and the total mass of gas in the interstellar medium. Use the data from the question 7.

Question 7

The density of the interstellar medium in our Galaxy is measured to be \(10^{-21} \mathrm{~kg} \mathrm{~m}^{-3}\) and consists mainly of hydrogen. Estimate how many hydrogen atoms per \(\mathrm{cm}^{3}\) are present in the Galaxy.