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Chapter 19: Problem 40

What observations would you make of a star to determine whether its primary source of energy is hydrogen fusion or helium fusion?

Short Answer

Expert verified
Mainly through the observation of the star's color, brightness, spectral analysis and fitting the star into the Hertzsprung-Russell diagram to determine its stellar evolution stage, it can be determined whether a star's energy comes from hydrogen fusion or helium fusion.

Step by step solution

01

Understanding Stellar Energy Production

Stars primarily generate their energy through the process of nuclear fusion. Hydrogen fusion is the dominant process in stars that are in the main sequence stage of their lifetime, like our Sun. In this process, hydrogen nuclei combine to form helium. When the star exhausts its hydrogen supply, it moves onto burning helium and other heavier elements.
02

Observing Star's Color and Brightness

Observations can begin by checking the star's color and brightness which are indicative of the star’s temperature. Stars undergoing hydrogen fusion tend to be in the main sequence, hence they are relatively cooler and less bright, compared to the intense brightness and high temperature of stars doing helium fusion.
03

Spectral Analysis

Spectral analysis can be done to determine the chemical composition of the star. Through this analysis, absorption lines matching with specific elements can be spotted. The larger presence of helium would indicate helium fusion.
04

Checking Stellar Evolution Stage

Observing the stage of stellar evolution that the star is currently in can be determinant. Main sequence stars are lean towards Hydrogen fusion while Red Giants lean towards Helium fusion at their core. Hence, fitting the star to the Hertzsprung-Russell diagram, a scatter plot of stars showing the relationship between the stars' absolute magnitudes or luminosities versus their stellar classifications or effective temperatures, can give pointers towards what fusion the star uses.

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Most popular questions from this chapter

Why does helium fusion require much higher temperatures than hydrogen fusion?

The Sun has increased in radius by \(6 \%\) over the past \(4.56\) billion years. Its present-day radius is \(696,000 \mathrm{~km}\). What was its radius \(4.56\) billion years ago? (Hint: The answer is not \(654,000 \mathrm{~km}\).)

What is a Roche lobe? What is the inner Lagrangian point? Why are Roche lobes important in close binary star systems?

What will happen inside the Sun 7 billion years from now, when it begins to mature into a red giant?

Why does a star's luminosity decrease after helium fusion begins in its core?
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