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Writer's pictureJohn Kim

Neptune experiences temperature change

Updated: Apr 3, 2023

The word “summer” typically reminds people of blazing hot temperatures. In Neptune, however, this is not the case. While it is estimated that Neptune’s southern hemisphere is in summer for about 41 years from 2005, there was a temperature drop of 8 degrees Celsius between 2003 and 2018, an anomaly that opposes how scientists initially predicted a temperature increase.


Four times larger than Earth, Neptune is the eighth and the most distant planet from the Sun in our solar system, and it takes 165 years to complete a full orbit around the Sun. Neptune is a chilly ice giant composed of primarily water, methane, and ammonia, with supersonic winds blowing around the clouds of the planet at speeds of more than 2000 kilometers per hour. Under the cold clouds of frozen methane, it is believed that there is an ocean of very hot water above a rocky core.


Scientists calculated Neptune’s temperatures by using ground-based telescopes and thermal cameras that measure the infrared light emitted by the planet. By collecting images of Neptune’s changing stratospheres over a 17 year period, scientists were able to capture the fluctuating temperatures of the southern hemisphere of Neptune.


Surprisingly, scientists have recently found that the temperature of Neptune’s southern hemisphere drastically increased by 11 degrees Celsius in just two years since 2018, suddenly reversing the questionable cooling that happened between 2003 and 2018. Since temperature changes occur slowly in Neptune given its 165-year orbital period, many astronomers are even more fascinated about these unprecedented yet dramatic temperature changes in the course of merely two years.

Thermal images indicate a warming in Neptune’s south pole between 2018 and 2020 (Source)


Many scientists attribute seasonal changes in Neptune’s atmospheric chemistry as the possible cause of this mysterious phenomenon. Methane in Netpune’s clouds may absorb the incoming sunlight and warm the atmosphere, while the amount of hydrocarbons controls the balance between heating and cooling. Random fluctuations in weather patterns triggered by Neptune’s dark vortices and solar flux may have also catalyzed this temperature change.


Although this phenomenon may sound like a distant issue, the rapidly changing temperatures in Neptune cannot be disregarded, given how global warming is accelerating faster than ever on Earth. Further research by the James Webb Space Telescope will be done later this year to investigate Neptune’s atmospheric chemistry and temperature. The outer space is still filled with questions and endless possibilities, and these future discoveries about the chemistry of Neptune’s atmosphere may help suggest new scientific reasons that catalyze the increase of temperature in Earth and other planets of our solar system.


Q&A:

Jennah: You mentioned in your article, “Methane in Netpune’s clouds may absorb the incoming sunlight and warm the atmosphere, while the amount of hydrocarbons controls the balance between heating and cooling.” What are some chemical qualities of methane that allow such phenomena to occur?

  • Both methane and hydrocarbons easily burn in air and generate carbon dioxide, consequently warming the atmosphere and contributing to global warming. The amount of these molecules therefore determine the balance between heating and cooling of the atmosphere in Neptune.


Anna: What more research do you think should be done by astronomers to support the hypothesis or statement that the mysterious phenomenon is caused by changes in Neptune’s atmospheric chemistry?

  • I believe that extreme weather events occurring in Neptune could be investigated in more detail to support the astronomers’ hypothesis, especially since there are many random fluctuations in Neptune’s weather patterns.


David: You said “many scientists attribute seasonal changes in Neptune’s atmospheric chemistry as the possible cause of this mysterious phenomenon”. Are there any studies that have been conducted that support these arguments of the scientists? Or are the arguments currently just speculations?

  • Yes, many researchers, including some from the National Aeronautics and Space Administration (NASA), believe that Neptune’s rapid changes of temperature may root from the seasonal changes in the planet’s atmospheric chemistry. However, much more research is currently needed, which still leaves much room for other possible causes of this phenomenon.


Hannah: How can discoveries about the chemistry of Neptune’s atmosphere help us learn more about Earth’s increase in temperature when the atmosphere of these two planets are very different?

  • Though the atmospheres of these two planets are very different, discoveries about Neptune's changing temperatures parallel how Earth’s rising temperatures are due to extreme weather patterns. Furthermore, substances that contribute to atmospheric warming such as methane and hydrocarbons are present in both planets, strengthening the connection.


Fabian: How will the changes in Neptune’s temperature provide insight into the global warming phenomenon?

  • Substances that contribute to atmospheric warming such as methane and hydrocarbons are present in both planets, and extreme weather patterns shown in Neptune may suggest how natural disasters may lead to even more drastic fluctuations of temperature on Earth.


Ian: How does Neptune’s 165-year orbital period account for slow temperature changes on Neptune?

  • It should be scientifically expected that Neptune’s temperature shifts very slowly due to the planet having a 165-year orbital period, which means that one season is about 41 years in Neptune. As a result, this makes the recent rapid changes of temperature in Neptune even more surprising to scientists.


Melissa: What is a potential effect that changes in Neptune would have on planet Earth?

  • While the changes in Neptune would not directly affect Earth, these two distant planets share a common similarity of rapidly changing environments and temperatures caused by increased extreme weather patterns.


Works Cited


Baker, Harry. “Astronomers Perplexed by Plummeting Temperatures in Neptune's Atmosphere.” LiveScience, Purch, 13 Apr. 2022, https://www.livescience.com/surprising-temperature-changes-on-neptune.


Dockrill, Peter. “Temperatures on Neptune Are Mysteriously Fluctuating, and It Doesn't Make Sense.” ScienceAlert, https://www.sciencealert.com/something-strange-is-happening-to-neptune-as-temperature-unexpectedly-fluctuates.


“In Depth.” NASA, NASA, 4 Aug. 2021, https://solarsystem.nasa.gov/planets/neptune/in-depth/.


“New Study Finds Unexpected Temperature Changes on Neptune – NASA Solar System Exploration.” NASA, NASA, 16 Apr. 2022, https://solarsystem.nasa.gov/news/2219/new-study-finds-unexpected-temperature-changes-on-neptune/#:~:text=New%20Study%20Finds%20Unexpected%20Temperature%20Changes%20on%20Neptune,-On%20Aug.&text=A%20new%20study%20reports%20an,C%20between%202003%20and%202018.%22&text=Researchers%2C%20including%20scientists%20from%20NASA,range%20between%202003%20and%202020.


Strickland, Ashley. “Neptune Just Experienced an Unexplained Temperature Shift.” CNN, Cable News Network, 11 Apr. 2022, https://www.cnn.com/2022/04/11/world/neptune-temperature-shifts-scn/index.html.



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