Chapter 11: Problem 6

How does the chemical composition of the present-day Sun's core compare to the core's composition when the Sun formed? What caused the change?

Short Answer

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Answer: The Sun's core has changed from being composed primarily of hydrogen and helium at its formation to having a lower percentage of hydrogen (approximately 60%) and a higher percentage of helium (38-40%) today. The primary cause of this change in chemical composition is the process of nuclear fusion, wherein hydrogen gets converted into helium.

Step by step solution

Sun's core formation composition

At its formation approximately 4.6 billion years ago, the Sun's core was composed primarily of hydrogen and helium, with traces of heavier elements. The Sun formed from a gas and dust cloud that consisted mostly of hydrogen (around 75%) and helium (around 25%), with only a small percentage of heavier elements also present. This composition is similar to the rest of the universe at the time, due to the fact that only hydrogen and helium were produced in the Big Bang.

Nuclear fusion in the Sun's core

Once sufficient pressure and temperature conditions were achieved within the Sun's core, nuclear fusion started. Hydrogen nuclei combined to form helium nuclei in a process called proton-proton chain reaction. This chain reaction involves the collision and conversion of protons (hydrogen nuclei) into neutrons, which ultimately combine to create helium nuclei. Energy in the form of light and heat is released during the process.

Current chemical composition of the Sun's core

Over the 4.6 billion years since its formation, the Sun's core has continuously fused hydrogen into helium, converting a significant portion of its original hydrogen content. The present chemical composition of the Sun's core is estimated to be approximately 60% hydrogen and 38-40% helium, with the remaining percentage made up of heavier elements.

Causes of the change in chemical composition

The change in the chemical composition of the Sun's core is predominantly due to the ongoing process of nuclear fusion that has been taking place. As hydrogen is steadily converted into helium within the core, the ratios of hydrogen to helium continue to change over time. The increase in helium content is accompanied by a hot and dense core, which leads to an increase in the Sun's energy production. This process will continue until the hydrogen in the Sun's core is depleted, and fusion will no longer be able to maintain its current state.

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How does the chemical composition of the present-day Sun's core compare to the core's composition when the Sun formed? What caused the change?

Short Answer

Step by step solution

Sun's core formation composition

Nuclear fusion in the Sun's core

Current chemical composition of the Sun's core

Causes of the change in chemical composition

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