The Hertzsprung-Russell Diagram and Stellar Evolution · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Reading the life story of stars

Science · Astronomy & Astrophysics · ages 21-22
Name ______________________   Date ____________

  1. Where do most stars fall on the diagram?

    • On the diagonal main sequence band
    • Scattered evenly everywhere
    • Only in the giant region

  2. What two quantities does the H-R diagram plot?

    • Mass against age
    • Surface temperature against luminosity
    • Distance against speed

  3. On the H-R diagram, temperature increases toward the left.

    Circle one:   True   False

  4. Two stars share one birthday but one has ten times the mass. Which leaves the main sequence first?

    • The lighter one, because it cools faster
    • Both leave at the same time
    • The heavier one, because it burns fiercely

  5. You measure a star with a hot spectrum and low luminosity. Where does it sit?

    • Among the giants above the sequence
    • Among the white dwarfs below the sequence
    • Outside the diagram entirely

  6. Why can a cluster H-R diagram reveal its age?

    • All members share one birthday, so mass alone sets the pace
    • Clusters contain only one star each
    • Cluster stars never evolve

  7. A student dates a cluster from one bright giant alone. What is wrong?

    • Giants cannot appear on the diagram
    • One star cannot show the turnoff pattern of the whole group
    • Brightness never depends on distance

  8. A cluster diagram shows the turnoff high on the sequence with bright giants. What does that say?

    • The cluster is young, since heavy stars still linger near the sequence
    • The cluster is ancient, since all stars became dwarfs
    • The cluster has no massive stars at all
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Answer key

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

Reading the life story of stars W1-mt_zMZDIB5TGc-s1

  1. On the diagonal main sequence band · Stars spend most of their lives on the main sequence.
  2. Surface temperature against luminosity · Each star becomes one point of temperature and luminosity.
  3. True · The temperature axis runs backward, hottest on the left.
  4. The heavier one, because it burns fiercely · Greater weight demands fiercer burning and a shorter life.
  5. Among the white dwarfs below the sequence · Hot plus faint means a compact white dwarf.
  6. All members share one birthday, so mass alone sets the pace · Same birthday and composition leave mass as the only difference.
  7. One star cannot show the turnoff pattern of the whole group · Age comes from where the sequence bends, which needs the group.
  8. The cluster is young, since heavy stars still linger near the sequence · A high turnoff means heavy fast burners have not yet left.
Worksheet · LightMySky