The useful idea
- Stars bound together
A galaxy is a physical system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity.
- Many galaxy shapes
Galaxies are categorised according to their visual characteristics such as elliptical, spiral, or irregular.
- Groups and clusters
Most galaxies are gravitationally organised into groups, clusters and superclusters.
Why this matters
Look for Galaxy the next time you notice this pattern in everyday life.
Try this
Look for Galaxy the next time you notice this pattern in everyday life.
Test your recall
Which idea belongs to the explanation of Galaxy?
- Groups and clusters
- Many galaxy shapes
- Stars bound together — correct
A galaxy is a physical system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity.