雅思阅读 109: Salty Clouds on the Pink Planet

Adapted from 'Salty clouds discovered on pink puffball planet', Scientific American, June 2026.

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A veil of salty clouds has been discovered on a puffy pink planet that has evaded imaging for more than a decade because it is so cold. If you were to travel 57 light-years to see the object, called GJ504b, you would view a world still glowing from the heat of its formation. The color is akin to a dark, cherry-blossom hue.

Despite its nickname, GJ504b might not actually be a planet at all. It is about 25 times the mass of Jupiter, according to new research. This mass straddles the line between gas giants and brown dwarf stars, leading astronomers to call the object a planetary-mass companion.

Astronomers have not been able to learn much about the pink planet from direct imaging with ground-based telescopes because the light from its sunlike host star overwhelms its relatively faint glow. Most directly imaged exoplanets are much hotter, at around 1,000 to 2,000 degrees Fahrenheit. Meanwhile temperatures on GJ504b reach just 550 degrees F.

In the new study, Aneesh Baburaj of Northwestern University and colleagues used the James Webb Space Telescope to capture the dim light emanating from the object. After accounting for the host star light, the team analyzed the wavelengths of light coming only from the companion. Each color in the spectrum is tied to a specific element. The atmosphere is full of the heavy elements carbon, oxygen, nitrogen and sulfur.

These elements were likely part of compounds such as water vapor, methane, carbon dioxide and ammonia. But after feeding the data into a computer model, the team was puzzled. At the top of the atmosphere, giant companions generally show a decrease in temperature. But the models indicated a small region where the temperature is constant, or isothermal. This is physically implausible without clouds.

After adding salty clouds to the model, the isothermal region disappeared, making the results plausible. The researchers think the clouds are full of chloride salts, such as potassium chloride, and sulfide salts, such as manganese sulfide. They also discovered that GJ504b is very old, likely formed between four billion and 2.5 billion years ago, which explains its chilly temperatures. Mysteries remain, including whether it is a giant planet or a brown dwarf.

Questions 1-5

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

1. How far away is GJ504b? A. 57 light-years B. 57 million miles C. 570 light-years D. 5,700 light-years
2. What is GJ504b approximately the mass of? A. 25 times Earth B. 25 times Jupiter C. 25 times the sun D. 2.5 times Jupiter
3. What is the temperature on GJ504b? A. About 550 degrees F B. About 1,500 degrees F C. About 5,500 degrees F D. Freezing
4. What telescope was used? A. Hubble B. James Webb C. Keck D. Spitzer
5. Why were the researchers puzzled? A. The atmosphere had no water B. An isothermal region was physically implausible without clouds C. The planet was too hot D. The star was too dim

Questions 6-10

Do the following statements agree with the information? Write TRUE, FALSE or NOT GIVEN.

6. GJ504b is definitely a planet.
7. The atmosphere contains carbon, oxygen, nitrogen and sulfur.
8. The salty clouds are made of water vapor.
9. GJ504b formed more than four billion years ago.
10. The planet has been directly imaged from Earth for a decade.

Questions 11-13

Complete the summary. Choose ONE WORD ONLY.

GJ504b is a pink planetary-mass 11. The team found a physically implausible 12 region that could only be explained by salty 13 clouds.

Answers

1. A 2. B 3. A 4. B 5. B
2. FALSE 7. TRUE 8. FALSE 9. TRUE 10. FALSE
3. companion 12. isothermal 13. clouds

Key Vocabulary

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