Galaxies and the universe · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Galaxies and the universe

Science · Space Systems & Earth's History · ages 12-13
Name ______________________   Date ____________

  1. Which statement about our Sun is true?

    • The Sun sits at the exact center of the Milky Way
    • The Sun is one star among billions in the Milky Way
    • The Sun is the biggest star in the Milky Way

  2. A light year is a measurement of what?

    • Distance
    • Time
    • Speed

  3. A light year measures how much time light takes to reach us, not a distance.

    Circle one:   True   False

  4. Light travels 1 light year in distance every year. A star is 4 light years away. How many years does its light take to reach Earth?

    Answer: ______________

  5. Light from the Sun takes about 8 minutes to reach Earth. Light from the next-nearest star takes about 4 years. Which is farther from Earth?

    • The Sun
    • They are the same distance
    • The next-nearest star

  6. These are shown out of order. Which choice lists them correctly from smallest to largest?

    Milky WayEarthUniverseSolar System
    • Earth, Solar System, Milky Way, Universe
    • Solar System, Earth, Milky Way, Universe
    • Earth, Milky Way, Solar System, Universe

  7. A star is 400 light years away. Why can't we visit it with current spacecraft?

    • Light years are actually very short distances
    • Space exploration only needs a few days for any distance
    • Current spacecraft are far too slow to cross such enormous distances within a human lifetime

  8. Maya says, 'A galaxy is a single giant star that lights up the whole universe.' What is wrong with her statement?

    • Nothing, that is correct
    • A galaxy is actually a huge collection of billions of stars, not one star
    • A galaxy is a planet, not a star
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Galaxies and the universe W1-mt_v9uYnIY5-B-s1

  1. The Sun is one star among billions in the Milky Way · The Sun is an ordinary star, one of over 100 billion stars in the Milky Way galaxy.
  2. Distance · A light year measures distance: how far light travels in one year, not how long something takes.
  3. False · A light year is a distance, the distance light travels in one year, even though the word year is in its name.
  4. 4 · Since a light year is how far light goes in a year, light from a star 4 light years away takes 4 years to arrive.
  5. The next-nearest star · 4 years of light-travel time is far longer than 8 minutes, so that star is enormously farther away than the Sun.
  6. Earth, Solar System, Milky Way, Universe · Earth sits inside the solar system, the solar system sits inside the Milky Way, and the Milky Way is one galaxy in the universe.
  7. Current spacecraft are far too slow to cross such enormous distances within a human lifetime · Light itself takes 400 years to cross that distance, and spacecraft travel far slower than light, so the trip would take vastly longer than a human lifetime.
  8. A galaxy is actually a huge collection of billions of stars, not one star · A galaxy like the Milky Way is a giant collection of billions of stars, gas, and dust held together by gravity, not a single star.
Worksheet · LightMySky