Galaxies and the universe
Describe the scale of the universe, including the structure of galaxies, the position of the Sun in the Milky Way, and the use of light years as a unit of distance, and appreciate why space exploration requires enormous timescales
Lesson
Set out your lesson
“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.”
Bring to the table
- Paper
- Pencil
- Ruler
Extra for the adult
Worked example. For the fictional star, 400 × 9.46 trillion km = 3,784 trillion km. At 0.001 light-year per year, the trip takes 400,000 years. The slower ship needs far longer than light.
Optional challenge. Explain why 400-year-old starlight tells us about the star’s past appearance.
What to notice. Keep both views, cards and calculation. Note help with units or arithmetic.
Share and support
Family records and proof options
Keep a record of your learning
Save photos, notes, and attendance. Export a proof packet for compliance or portfolio reviews.
Learning resources
Extra practice links — they do not replace Gakuva’s teaching approach.
NASA Space Place · Practice link — not the full lesson
Sun
Before you open · source notes
Sun supports Galaxies and the universe. An adult previews and guides; this is a learning page, not a scored quiz.
Free educational page, no sign-in required for the tested path.
Before you openAsk the learner one fact they learned and one question they still have.
Opening this link does not save learning or assess mastery.
Source, access and review notes
Public NASA Space Place page. An anonymous GET on 2026-11-12 returned HTTP 200 with no login or payment prompt for this URL. Opening the link does not save practice or assess mastery. An adult should preview and guide the learner.
NASA Space Place. “Sun.” External page; Gakuva does not copy, host, embed, or redistribute materials.
Unknown — link only
Check understanding
- Defines a light year as the distance light travels in one year
- Describes the structure of a galaxy and states that the Sun is a star in the Milky Way galaxy
- Compares the distances within the solar system with the distances between stars and between galaxies, expressing them in appropriate units
“If your child heard that a star is 400 light years away, could they explain what a light year means, roughly how far that is, and why we will never be able to visit it with current spacecraft?”
Curriculum record
- Type
- Conceptual
- Subject
- Science
- Domain
- Space Systems & Earth's History
- Age range
- Ages 12–13
Standards