Science 10 with CSS teacher

Because some distances in space are so huge, astronomers use three terms to describe the kinds of distances they are talking about.

• Interplanetary distances are the distances between planets. These are measured in kilometres (km), or in Astronomical Units (AU). One AU is equal to the distance between the Earth and the Sun—about 150 000 000 km.
• Interstellar distances are distances between the stars in a galaxy. These distances are measured in light-years.
• Intergalactic distances are the distances between galaxies, and are also measured in light-years.