The Sun's Life and Fusion
Aligned to HS-ESS1-1 — Next Generation Science Standards.
What this lesson teaches
The sun shines because gravity squeezes its core hot and dense enough to fuse hydrogen nuclei into helium. Each fusion converts a tiny bit of mass into energy, and the sun has enough hydrogen fuel to last about 10 billion years.
Worked examples
Example 1
In the sun's core, four hydrogen nuclei fuse into one helium nucleus. The helium weighs slightly less than the four hydrogens, and that missing mass is released as the light and heat that reach Earth eight minutes later.
Example 2
The sun converts about 4 million tonnes of mass into energy every second and will still last another 5 billion years.
Example 3
E = mc² is why the numbers are so large. A tiny mass times the speed of light squared is an enormous amount of energy.
Practice questions
- Observe: The sun's brightness has stayed steady over human history. What does that suggest about how fast it burns its fuel?
- Model: Sketch what happens to mass and energy when hydrogen fuses into helium in the core.
- Explain: The sun is about 4.6 billion years old and lives roughly 10 billion years. Argue whether it is closer to its start, middle, or end, and predict what runs out.
Watch the lesson
Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.
▶ Watch this lessonEn español
La vida del Sol y la fusión
El Sol brilla porque la gravedad comprime su núcleo hasta hacerlo tan caliente y denso que fusiona núcleos de hidrógeno en helio. Cada fusión convierte un poco de masa en energía, y el Sol tiene suficiente hidrógeno para durar unos 10 mil millones de años.
Ejemplo 1: En el núcleo del Sol, cuatro núcleos de hidrógeno se fusionan en uno de helio. El helio pesa un poco menos que los cuatro hidrógenos, y esa masa faltante se libera como la luz y el calor que llegan a la Tierra ocho minutos después.
Ejemplo 2: El sol convierte unos 4 millones de toneladas de masa en energía cada segundo y aun así durará otros 5 mil millones de años.
Ejemplo 3: E = mc² es la razón de que los números sean tan grandes. Una masa diminuta por la velocidad de la luz al cuadrado es una cantidad enorme de energía.
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