This would be an activity for science. I would let students make galaxy playdough. They would extent it to create their own constellations. Then a writing activity would be completed. This writing could be in any format we have worked on in writing. I would use the hambuger rubric for assessment.
This DIY recipe for Kinetic Sand only takes 3 ingredients, and costs about a third of what commercial brands of Kinetic Sand retails for. Kids love sensory play like this, and will occupy them for hours. See how to make your own Kinetic Sand here! http://livingithaca.com/diy/make-kinetic-sand/