雅思阅读 13: The Planet That Outlived Its Star（逃过恒星之死的行星）

改编自 Scientific American / Nature（2026年7月）。雅思阅读 Section 3 难度，约 1050 词。 素材来源：https://www.scientificamerican.com/article/this-planet-survived-the-death-of-its-star-and-kept-its-atmosphere/

Reading Passage

A. The universe has a flair for the unlikely. In 2020 astronomers announced the discovery of WD 1856 b, a gas giant orbiting the burned-out core of a sunlike star — a white dwarf — in a tight, 34-hour orbit. The discovery was baffling enough. Stars like the Sun end their lives by swelling into red giants, swallowing the inner planets before collapsing into dense stellar embers. For a Jupiter-sized world to survive that upheaval, let alone arrive in such a close orbit, seemed to defy physical probability. Now, a study published in Nature in July 2026 has deepened the mystery: not only did WD 1856 b survive, but it retains a substantial atmosphere, and it is still warm. "It was unlike any other exoplanet spectrum we've seen," says lead author Ryan MacDonald of the University of St Andrews, "which caused a fair amount of head-scratching in our team." The object had first turned up in 2020 in data from NASA's Transiting Exoplanet Survey Satellite, which monitors broad swathes of sky for stars that dim periodically as a world passes in front of them. Because the host white dwarf lies a mere eighty light-years away — close on the cosmic scale — the system offers astronomers an unusually bright and accessible target for the kind of detailed atmospheric follow-up that this study depends on.

B. To understand why this matters, it helps to recall how a sunlike star dies. Lacking the mass to explode as a supernova, it swells into a red giant, shedding its outer layers and collapsing into a white dwarf roughly the size of Earth but containing most of its original mass. Any planet in the inner system is either engulfed by the expanding envelope or flung outward as the star's gravitational grip weakens. The conventional expectation was that no planet could survive within the red giant's reach and re-emerge intact. Yet WD 1856 b circles its white dwarf at a distance so close that a year on the planet lasts just 34 hours. Two competing explanations have emerged. The first holds that the planet was swallowed by the dying star, survived passage through its envelope, and was spat back out into a tight orbit as the star collapsed. The second proposes that the planet began at a safer distance and migrated inward later, under the gravitational influence of other objects in the system. Either pathway is unforgiving. During the red-giant phase the star's swollen envelope, though far thinner than the body of a main-sequence star, is still dense enough to drag on any world that dips inside it, heating that world to thousands of degrees and threatening to strip away its outer layers before the remnant settles into its long cooling decline.

C. The answer, the researchers found, lay in the planet's heat. By combining temperature measurements with estimates of the planet's mass and models of how giant planets cool over time, the team effectively rewound its thermal clock. If the planet had been swallowed and reheated inside the red giant, it would retain far more residual warmth than was actually observed. The measured temperature was consistent with a world that had orbited at a comfortable distance for more than a billion years before spiralling inward, gradually losing orbital energy as it passed close to the white dwarf. "Each time it makes a close pass," MacDonald explains, "it would lose a little orbital energy into heat, which would move the furthest part of the orbit slightly closer." Viewed in infrared light, the planet would be visible glowing at the height of this process. The reasoning rests on a principle familiar to planetary scientists: a giant planet contracts and radiates away its primordial heat gradually over hundreds of millions of years, so its present temperature acts as a rough readout of its thermal history. By modelling that cooling, the team could distinguish a world that had always lived quietly at a safe distance from one that had endured the furnace of the stellar envelope.

D. The discovery carries implications for our own cosmic future. Roughly five billion years from now, the Sun will follow the same trajectory: red giant, planetary nebula, white dwarf. Earth, almost certainly, will not survive. But the solar system's outer gas giants — Jupiter and Saturn — may persist for billions of years longer, circling the fading ember in the dark. "Jupiter has a long life ahead of it, even after the leftover core of the Sun is merely a smouldering ember," MacDonald observes. If astronomers of a future civilisation are around to study it, they might one day read Jupiter's atmosphere as a fossil record of a planetary system that outlasted its star. WD 1856 b offers a preview of what that analysis might reveal. The inner planets face near-certain destruction: Mercury and Venus will be engulfed outright, and even Earth may be dragged inward as the dying Sun loses mass and its gravitational grip slackens. Only the outermost worlds are expected to outlive the fire.

E. More broadly, the study opens a new avenue in exoplanet atmospheric science. Until now, astronomers studying white-dwarf systems have focused almost entirely on the debris of disrupted planets — the rocky material that rains onto the stellar surface and betrays the composition of shattered bodies. WD 1856 b demonstrates that intact, atmosphere-bearing worlds can survive in these graveyard systems, and that their atmospheres are detectable with current instruments. The find also underscores a recurring lesson of exoplanet research: nature invents configurations that theory did not predict. "Exoplanet science is a never-ending story of reimagining what is possible," MacDonald says. Whether the audience is a science-fiction fan, a working astronomer or a schoolchild, the question of what becomes of planetary systems when their star dies is no longer purely theoretical. Future observations, using instruments already planned, will test whether such planets retain the chemistry of their formation epochs or are reprocessed by the harsh radiation that bathes them near their stellar embers. For now, WD 1856 b stands as a reminder that the end of a star need not mean the end of its worlds.

Questions 1-4

Choose the correct heading for paragraphs B, C, D and E from the list of headings below.

List of Headings i. How the Sun will die in five billion years ii. Two competing explanations for a tight orbit iii. Why the planet's temperature settles the argument iv. The manufacture of white dwarf stars v. What the discovery means for our own solar system vi. A new chapter in the study of planetary graveyards vii. How the planet was swallowed by the red giant

1. Paragraph B: ____
2. Paragraph C: ____
3. Paragraph D: ____
4. Paragraph E: ____

Questions 5-8

Choose the correct letter, A, B, C or D.

5. Why is WD 1856 b considered puzzling? A. It is larger than Jupiter but orbits a white dwarf. B. It survived the red-giant phase and remains in a very close orbit. C. It has no atmosphere despite being a gas giant. D. It orbits its star backwards.

6. What did the temperature measurements suggest? A. The planet was reheated inside the red giant. B. The planet migrated inward from a wider orbit. C. The white dwarf is hotter than expected. D. The planet is still generating internal heat.

7. What does MacDonald say about Jupiter's future? A. It will be swallowed when the Sun becomes a red giant. B. It may survive long after the Sun becomes a white dwarf. C. It will lose its atmosphere within a billion years. D. It will move closer to the remnant Sun.

8. The study is significant because it shows that A. white dwarfs cannot support any planetary system. B. intact planets with atmospheres can survive in white-dwarf systems. C. all gas giants are eventually swallowed by red giants. D. exoplanet atmospheres are impossible to detect.

Questions 9-13

Do the following statements agree with the claims of the writer?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

9. A year on WD 1856 b lasts about 34 Earth days.
10. The planet's observed temperature was lower than expected if it had been swallowed by the red giant.
11. Earth will likely survive the Sun's red-giant phase.
12. Previous white-dwarf studies focused on intact, atmosphere-bearing planets.
13. The research team observed the planet directly with a visible-light telescope.

Questions 14-15

Complete the summary below using NO MORE THAN TWO WORDS from the passage.

When a sunlike star dies, it sheds its outer layers and collapses into a (14) __________. WD 1856 b is remarkable because it survived this process and still retains an (15) __________.

答案与解析

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