Our Interstellar Medium | NASA Goddard FriendsofNASA.org: Our Milky Way galaxy is home to more than 100 billion stars that are often separated by trillions of miles. The spaces in between, called the interstellar medium, are not empty—they are sprinkled with gas and dust that are both the seeds of new stars and the leftover crumbs from stars long dead. Studying the interstellar medium with observatories like NASA’s upcoming Nancy Grace Roman Space Telescope will reveal new insight into the galac