The Lives of Stars
Written by Studio AM.
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A star is not eternal; it is born, lives, and dies over spans that dwarf human history. Stars begin within vast clouds of gas and dust drifting through space. Gravity slowly pulls a clump of this material inward, and as the clump shrinks it grows denser and hotter. When the core becomes hot enough, hydrogen nuclei begin fusing to form helium, releasing enormous energy and igniting the star.
For most of its life a star maintains a steady balance: the outward push of this fusion energy resists the inward crush of gravity. When hydrogen fuel in the core runs low, that balance breaks, and the star's fate depends on its mass.
A modest star like the Sun swells into a red giant, sheds its outer layers, and leaves a hot core called a white dwarf, which gradually cools. A far more massive star can collapse and explode as a supernova, sometimes briefly shining as brightly as a galaxy. Other massive stars may collapse with little visible explosion. The debris of such explosions scatters heavy elements across space. Gathered by gravity over billions of years, that scattered debris becomes the raw material for new clouds, new stars, and the planets that circle them.
Remarkably, the carbon in living bodies and the iron in blood were forged inside ancient stars, and later spread into the material from which our solar system formed. Many elements in living cells therefore connect the history of life on Earth with earlier generations of stars.
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Questions
Choose an answer. The explanation appears after you answer.
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Question 1 of 4
Which factor does the passage emphasize in explaining a star’s eventual fate?
The answer is B: Its mass
The passage states that the star’s fate depends on its mass, then contrasts Sun-like and much more massive stars.
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Question 2 of 4
What keeps a star in a steady balance for most of its life?
The answer is B: Fusion energy pushing out against gravity pulling in
The passage says the 'outward push of this fusion energy resists the inward crush of gravity.'
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Question 3 of 4
As used in the passage, 'forged' most nearly means
The answer is B: created or formed
Heavy elements like carbon and iron were 'forged inside ancient stars,' meaning created or formed there.
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Question 4 of 4
Which statement best expresses the central idea of the passage?
The answer is C: Stars live and die, scattering elements that form planets and living things
The passage traces a star's birth, life, and death, then shows how the scattered debris becomes new stars, planets, and even the carbon and iron in our bodies.
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