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8th grade · Science · Unit 10 of 13

Stars, Galaxies & the Universe

Star life cycles, the H-R diagram, kinds of galaxies, and the Big Bang.

What your child practices

Practices the life cycle of stars and classifying stars on the Hertzsprung-Russell diagram, spiral, elliptical and irregular galaxies and where our solar system sits in the Milky Way, and the evidence (such as galaxies moving apart and leftover radiation) for the Big Bang theory of the origin of the universe.

Texas Essential Knowledge and Skills (TEKS) teks student expectation: 8.9(A); 8.9(B); 8.9(C) · star life cycles and the H-R diagram, kinds of galaxies, and evidence for the origin of the universe

How we explain it

Children can open this short lesson before they practice.

  1. Stars form in nebulas. A Sun-like star becomes a red giant, then a white dwarf.
  2. Very massive stars explode as supernovas and leave a neutron star or a black hole.
  3. On an H-R diagram, most stars lie on the main sequence. Galaxies are spiral, elliptical or irregular.

Example: After the main sequence, what does a Sun-like star swell into? It runs low on hydrogen in its core. It grows huge and cooler and redder. Answer: a red giant

Stars, Galaxies & the Universe in Texas

In the Texas Essential Knowledge and Skills (TEKS), this is unit 10 of 13 in 8th grade Science, after Water, Acids & Bases and before Weather, Winds & Hurricanes.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: Texas Education Agency (TEA)

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    Where is our solar system in the Milky Way?

    • Outside the galaxy
    • In the central black hole
    • At the exact center
    • In a spiral arm, about halfway from the center

  2. Question 2

    The Hertzsprung-Russell diagram compares stars' luminosity and…

    • distance from Earth
    • surface temperature
    • age only
    • number of planets

  3. Question 3

    Which stars live the shortest lives?

    • The smallest stars
    • The most massive stars
    • All stars live the same time
    • Medium stars like the Sun

  4. Question 4

    On an H-R diagram, most stars lie along a band called the…

    • dwarf line
    • main sequence
    • giant branch
    • Milky Way

  5. Question 5

    The Milky Way is a…

    • irregular galaxy
    • spiral galaxy
    • nebula
    • elliptical galaxy

  6. Question 6

    Elements heavier than iron are made mainly in…

    • supernovas and star collisions
    • comets
    • the Moon
    • planets

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