The Sun as a Star: Photosphere, Corona and the Activity Cycle · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

The Sun wears a hot crown

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

  1. How is the tenuous hot corona observed?

    • Bare eyes at noon
    • Coronagraphs or X ray telescopes
    • Ultraviolet alone for the surface

  2. What marks the visible photosphere?

    • 5800 with an absorption spectrum
    • A million with an absorption spectrum
    • 5800 glowing only in X rays

  3. The solar activity cycle lasts about how many years?

    Answer: ______________

  4. What is a solar flare?

    • Large scale escape of plasma outward
    • Sudden local release of stored stress
    • Steady burning of surface gas

  5. Differential rotation winds the field up. What is a sunspot pair?

    • A cool cloud passing before the Sun
    • A shadow cast by a planet
    • A magnetic loop punching through the surface as a spot pair

  6. Moving outward, density falls yet the corona runs far hotter. Why does that puzzle scientists?

    • Density falls steeply even as heat spikes
    • Density climbs while heat stays flat
    • Both stay exactly constant outward

  7. What must any solution to the hot corona problem demonstrate?

    • Show the surface cooling below the corona
    • Show waves or bursts lifting enough energy to the glow
    • Show magnetism playing no role at all

  8. An Earth aimed ejection leaves the Sun. What warning window do forecasters hold?

    • About eleven years of slow drift
    • About eight minutes like sunlight
    • About one to three days of cruise time
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Answer key

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

The Sun wears a hot crown W1-mt_AMIkiU7wRz-s1

  1. Coronagraphs or X ray telescopes · The faint million degree crown needs blocked discs or high energy eyes.
  2. 5800 with an absorption spectrum · The visible surface sits near 5800 and imprints absorption lines.
  3. 11 · Spot counts march through roughly eleven years and flip polarity each round.
  4. Sudden local release of stored stress · Reconnection frees wound stress in a flash, while ejections throw matter free.
  5. A magnetic loop punching through the surface as a spot pair · Wound fields turn buoyant, pierce the surface, and show as paired spots.
  6. Density falls steeply even as heat spikes · Thinning air should cool, so the spike defies plain outward heat flow.
  7. Show waves or bursts lifting enough energy to the glow · Only an upward energy courier that pays the heat bill closes the case.
  8. About one to three days of cruise time · Charged clouds need roughly a day or three to arrive, fixing the warning window.
Worksheet · LightMySky