Life Cycle of a Star · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

The Life Cycle of a Star

Science · Space Systems & Earth's History · ages 13-14
Name ______________________   Date ____________

  1. Which two endings are possible only for very massive stars?

    • White dwarf or red giant
    • Neutron star or black hole
    • Nebula or protostar

  2. Look at the star's life cycle below. What is stage 1, the highlighted stage, called?

    NebulaProtostarMain seqRed giantWhite dwarf
    • Nebula
    • Red giant
    • White dwarf

  3. Nuclear fusion inside a star can build elements heavier than hydrogen and helium.

    Circle one:   True   False

  4. A star ten times heavier than the Sun finally runs out of fuel. What happens next?

    • It explodes as a supernova, leaving a neutron star or black hole
    • It quietly shrinks into a white dwarf
    • It turns back into a nebula

  5. Put these stages of a Sun-like star in the order they happen.

    • Red giant, then nebula, then main sequence
    • Main sequence, then nebula, then red giant
    • Nebula, then main sequence, then red giant

  6. Count the stages shown in this Sun-like star's life cycle. How many stages are there?

    NebulaProtostarMain seqRed giantWhite dwarf

    Answer: ______________

  7. Two stars start as identical nebulae, but Star A is far more massive than Star B. What happens to each?

    • Both stars will always end the same way, since they started the same way
    • Star B will explode first because smaller stars burn fuel faster
    • Star A is more likely to end in a supernova and leave a neutron star or black hole, while Star B likely becomes a white dwarf

  8. A classmate says the iron in your blood came from the Sun exploding. What's the mistake?

    • Iron does not come from stars at all
    • The Sun isn't massive enough to explode as a supernova; the iron came from a different, more massive star that died long ago
    • The Sun already exploded when the solar system formed
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Answer key

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

The Life Cycle of a Star W1-mt_lHasFmgvnT-s1

  1. Neutron star or black hole · Massive stars explode as a supernova and leave behind a neutron star or, if massive enough, a black hole.
  2. Nebula · Every star's life starts inside a nebula, a cloud of gas and dust pulled together by gravity.
  3. True · Fusion fuses lighter atoms into heavier ones, like carbon, oxygen, and iron.
  4. It explodes as a supernova, leaving a neutron star or black hole · Only stars far more massive than the Sun end their lives in a supernova.
  5. Nebula, then main sequence, then red giant · A star starts as a nebula, spends most of its life on the main sequence, then swells into a red giant.
  6. 5 · Nebula, protostar, main sequence, red giant, and white dwarf: five stages in all.
  7. Star A is more likely to end in a supernova and leave a neutron star or black hole, while Star B likely becomes a white dwarf · A star's mass decides its ending: heavier stars burn fast and end dramatically, while lighter stars like the Sun end quietly.
  8. The Sun isn't massive enough to explode as a supernova; the iron came from a different, more massive star that died long ago · Sun-like stars end quietly as white dwarfs. Making enough iron takes a supernova from a much more massive star.
Worksheet · LightMySky