A galaxy is a vast gravitationally bound system of stars, gas, dust and dark matter. The Milky Way has a disk with spiral arms and a central bulge, surrounded by a halo. Our Sun lies in its disk, not at its centre. A light-year is a distance: about 9.46 trillion km, the distance light travels in one year. Safety: Paper task only; no night outing or space-travel simulation. Stop: Stop at these reference values and one ideal journey. No mission plan, map download or spacecraft ranking.

Materials: Paper; Pencil; Ruler 1. Draw a face-on spiral disk with a central bulge and a surrounding halo outline. Add a Sun dot partway out in the disk. Beside it draw an edge-on thin disk and central bulge. Label schematic; not measured structure or a map of individual stars. 2. Write distance cards: Earth–Sun, 1 AU, about 150 million km and about 8 light-minutes; Sun–nearest other star, about 4.25 light-years; Milky Way disk width, over 100,000 light-years; Milky Way–Andromeda, about 2.5 million light-years. Sort small to large. The disk width is an extent, not a journey to a named object. 3. Draw four separate bars, one per card. Label them not on a shared scale. Explain why a small solar-system drawing cannot also show interstellar and intergalactic distances clearly. 4. Use a fictional star 400 light-years away. Convert using the supplied 9.46 trillion km per light-year. Then use an illustrative ship speed of 0.001 light-year per year, ignoring acceleration, to estimate travel time. This is not a real spacecraft capability. 5. Explain that the light takes 400 years to arrive, but the hypothetical slower ship takes much longer. Do not say a light-year is a time unit or that all future travel is impossible. Done: Finish the two galaxy views, four ordered distance cards and the stated hypothetical travel estimate. Proof: Keep both views, cards and calculation. Note help with units or arithmetic. Stop: Stop at these reference values and one ideal journey. No mission plan, map download or spacecraft ranking.