Interstellar means between or among the stars. When astronomers talk about interstellar space, they mean the vast emptiness between star systems, far beyond any planet's orbit. The interstellar medium is the thin gas and dust that drifts through this space, sometimes forming beautiful clouds called nebulae where new stars are born.

Our sun is about four light-years from the nearest star, Proxima Centauri. That enormous gap is interstellar space. To cross it, you'd need to travel faster than any spacecraft humans have ever built.

Science fiction stories often feature interstellar travel, where spaceships journey between different star systems, visiting alien worlds. In reality, interstellar distances are so huge that even our fastest probes would take tens of thousands of years to reach another star. The Voyager 1 spacecraft, launched in 1977, entered interstellar space after traveling for over 35 years.

Scientists study interstellar molecules and magnetic fields to understand how galaxies work. Some researchers even imagine future interstellar missions that might reach nearby stars within a human lifetime, though we'd need revolutionary new technologies to make that possible.