3.5 Key Terms

Astronomical unit (AU): the average Earth-Sun distance. 3.1

Constellation: one of the 88 sections into which astronomers divide the sky, each named after a prominent star pattern within it. 3.2

Interstellar dust: dust that, together with a sparse distribution of gas, collects into enormous clouds in many places in the Galaxy, becoming the raw material for future generations of stars. 3.1

Milky Way Galaxy: a single collection of stars which contains the Sun, the stars visible to the unaided eye from Earth, as well as hundreds of billions of other stars. 3.1

Moon: our nearest astronomical neighbour which is also Earth’s satellite. 3.1

Planet: a body of significant size that orbits a star and does not produce its own light. 3.1

Quasars: brilliant centres of galaxies, glowing with the light of an extraordinarily energetic process. 3.2

Star: a large body that consistently produces its own light. 3.1

Superclusters:  when clusters of galaxies themselves form into larger groups. 3.2