Kristen is creating a model of a galaxy. On a piece of paper, she draws many dots to represent stars. In order to make her model more accurate, she adds a key.

Along with the stars, Kristen shall also show effect of gas, dust and solar system in the galaxy.

Explanation:

Galaxy is a collection of various stars but these are bound to each other in a gravitational bound system. Along with the stars, the galaxy also consists of dust, gas and other kind of dark matter.

The solar systems are also consisted in the galaxy. According to the scientists, there are one hundred billion galaxies in the universe and all the galaxies consisting of a combination of all this.