VOA科学技术2023--Study: Neptune’s Disappearing Clouds Linked to Solar Cycle

Study: Neptune¹’s Disappearing Clouds Linked to Solar Cycle

Scientists say they have discovered new evidence that cloud activity on Neptune is linked to atmospheric² changes on the planet caused by the sun.

Researchers say the evidence is based on observations collected by several telescopes over a period of nearly 30 years. Data was collected by the Hubble Space Telescope – operated by the American space agency NASA – as well as the W.M. Keck Observatory³ in Hawaii and the Lick Observatory in California.

Astronomers⁴ recorded atmospheric changes on Neptune as they examined the cloud data. The researchers found that the changes followed the sun's natural cycle. Each natural cycle, known as the solar cycle, lasts about 11 years.

During this cycle, the sun's magnetic field completely flips⁶. This means the sun's north and south magnetic poles change places. They then flip⁵ back after another 11 years. Before the flip, a major increase in solar activity happens. This can send powerful collections of solar particles shooting through space.

The scientists who examined the telescope data said they found that Neptune appeared brightest in 2002, then dimmed in 2007. The planet became bright again in 2015, but then darkened in 2020 to the dimmest level ever observed.

The team said the observations also showed Neptune lost nearly all of its clouds beginning in 2019.

Astronomers at the University of California, Berkeley (UC Berkeley) led the research. They recently reported their findings in a study in the publication Icarus.

Imke de Pater is a retired⁷ professor of astronomy at UC Berkeley and was the lead writer of the study. She said in a statement she was surprised by how quickly clouds disappeared on Neptune. She noted⁸ cloud activity had dropped sharply "within a few months."

"Even four years later, the images we took this past June showed the clouds haven't returned to their former levels," said Erandi Chavez. She is a student at Harvard University's Center for Astrophysics who took part in the study while at UC Berkeley.

"This is extremely exciting and unexpected," Chavez said. She noted the finding was unusual "since Neptune's previous period of low cloud activity was not nearly as dramatic and prolonged."

Neptune, about four times wider than Earth, is the eighth and most distant major planet orbiting our sun, NASA says. It receives sunlight with only about 0.1 percent intensity⁹ of our planet. For this reason, the researchers found it surprising that Neptune would be heavily influenced by solar activity. The planet also receives intense winds that can blow around clouds.

The scientists looked at images captured by the different telescopes. They discovered clear patterns between seasonal¹⁰ changes in Neptune's cloud cover and the solar cycle. The team found that during periods when the sun gave off more intense ultraviolet (UV) light, more clouds appeared on the planet two years later.

De Pater said the newly discovered data provides "the strongest evidence yet that Neptune's cloud cover correlates with the sun's cycle." He added the findings "support the theory that the sun's UV rays, when strong enough, may be triggering a photochemical reaction that produces Neptune's clouds." Photochemical is a term relating to how chemicals are affected¹¹ by light.

The researchers are continuing to follow cloud activity on Neptune. They noted that the latest images taken of the planet, in June 2023, showed clouds started to return. The team says this finding further strengthens their evidence. This is because the scientists see a link between the increasing cloud cover and the release of intense UV light over the past two years.

The researchers say further study is needed to confirm their latest results. They say the research will be important not only for learning more about Neptune, but can also help scientists gain a better understanding of how similar planets outside our solar system behave.

Words in This Story

cycle – n. a series of events that happen in a particular order and are often repeated

flip – v. to turn something onto a different side

dim – adj. not bright or clear

dramatic – adj. very sudden or noticeable

prolonged – adj. continuing for a long time

pattern – n. a particular way something is done or repeated

correlate – v. link pieces of information or things together

trigger – v. to make something begin to happen

1 Neptune   

n.海王星

参考例句：

• Neptune is the furthest planet from the sun.海王星是离太阳最远的行星。
• Neptune turned out to be a dynamic,stormy world.海王星原来是个有生气、多风暴的世界。

2 atmospheric   

adj.大气的，空气的；大气层的；大气所引起的

参考例句：

• Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
• Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。

3 observatory   

n.天文台，气象台，瞭望台，观测台

参考例句：

• Guy's house was close to the observatory.盖伊的房子离天文台很近。
• Officials from Greenwich Observatory have the clock checked twice a day.格林威治天文台的职员们每天对大钟检查两次。

4 astronomers   

n.天文学者，天文学家( astronomer的名词复数 )

参考例句：

• Astronomers can accurately foretell the date,time,and length of future eclipses. 天文学家能精确地预告未来日食月食的日期、时刻和时长。 来自《简明英汉词典》
• Astronomers used to ask why only Saturn has rings. 天文学家们过去一直感到奇怪，为什么只有土星有光环。 来自《简明英汉词典》

5 flip   

vt.快速翻动；轻抛；轻拍；n.轻抛；adj.轻浮的

参考例句：

• I had a quick flip through the book and it looked very interesting.我很快翻阅了一下那本书，看来似乎很有趣。
• Let's flip a coin to see who pays the bill.咱们来抛硬币决定谁付钱。

6 flips   

轻弹( flip的第三人称单数 )； 按（开关）； 快速翻转； 急挥

参考例句：

• Larry flips on the TV while he is on vacation in Budapest. 赖瑞在布达佩斯渡假时，打开电视收看节目。
• He flips through a book before making a decision. 他在决定买下一本书前总要先草草翻阅一下。

7 retired   

adj.隐退的，退休的，退役的

参考例句：

• The old man retired to the country for rest.这位老人下乡休息去了。
• Many retired people take up gardening as a hobby.许多退休的人都以从事园艺为嗜好。

8 noted   

adj.著名的，知名的

参考例句：

• The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
• Jim is noted for arriving late for work.吉姆上班迟到出了名。

9 intensity   

n.强烈，剧烈；强度；烈度

参考例句：

• I didn't realize the intensity of people's feelings on this issue.我没有意识到这一问题能引起群情激奋。
• The strike is growing in intensity.罢工日益加剧。

10 seasonal   

adj.季节的，季节性的

参考例句：

• The town relies on the seasonal tourist industry for jobs.这个城镇依靠季节性旅游业提供就业机会。
• The hors d'oeuvre is seasonal vegetables.餐前小吃是应时蔬菜。

11 affected   

adj.不自然的，假装的

参考例句：

• She showed an affected interest in our subject.她假装对我们的课题感到兴趣。
• His manners are affected.他的态度不自然。