Neptune’s Temperature Drops Baffle Scientists

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Courtesy of Hphotostudio (Pixabay CC0)

Neptune is Earth’s solar system’s outermost planet. It is a frigid, far-flung, and enigmatic world. During the past two decades, astronomers were puzzled by the surprising drop in atmospheric temperatures. Above the turbulent weather layer, Neptune has a fairly steady region.

The scientists focused on the Neptune stratosphere and expected to find it heating up on the side facing earth as its southern hemisphere summer got underway. Instead, the temperatures declined significantly. The 17 years of study on the planet’s stratosphere revealed that the temperature fell between 46.4 degrees F (8 C) to minus 286.6 degrees F (minus 117 C). Meanwhile, no significant variability in the troposphere, in the colder weather layer, where temperatures were as low as minus 433.4 degrees F (minus 223 C).

With regional deviations, the temperature changes were roughly distributed. Its Southern tropics chilled, and warmed, then chilled again.

Neptune is 49,250 kilometers, about four spans broader than Earth. It orbits more than 30 times as far away from the Sun at a moderate distance of 4.5 billion kilometers needing about 165 Earth years to complete a single orbit around the Sun.

Courtesy of University Leicester (Flickr CC0)

It circumnavigates the sun at 4.5 kilometers, more than 30 times as far away from the Sun as Earth, requiring about 165 Earth years to complete a single orbit around the Sun. Neptune experiences the same seasons as Earth but much longer.

Neptune has a dynamic atmosphere and the most powerful winds on any planet. However, it lacks a solid surface, mainly helium, hydrogen, and methane. It is different from Uranus, which had no obvious weather patterns.

Scientist assessments were based on more than 95 thermal-infrared images based on ground-based telescopes in Chile and Hawaii between 2003 and 2020. The most thorough Neptune atmospheric temperature study to date.

The planet is among the least-explored of the solar system because of its distance making it difficult to study from Earth. Michael Roman, lead author of the study published in Planetary Science Journal, and a postdoctoral researcher at the University of Leicester in England said:

The atmosphere appears more complicated than we had naively assumed, which, unsurprisingly, seems to be a general lesson that nature teaches scientists again and again. I think Neptune is very intriguing to many of us because we still know so little about it. I suspect the overall temperature drop may most likely be due to changes in the atmospheric chemistry, which responds to changing seasonal sunlight and, in turn, alters how effectively the atmosphere cools.

NASA’s Voyager 2 was the only spacecraft to fly past Neptune. It did so in 1989.

Written by Janet Grace Ortigas
Edited by Cathy Milne-Ware


ABC News: Astronomers baffled by dramatic temperature changes on Neptune
Sky News: Scientists discover mysterious changes in Neptune’s temperature
9 News: Neptune just experienced an unexplained temperature shift

Featured and Top Image Courtesy of Hphotostudio’s Pixabay Page – Creative Commons License
Inset Image Courtesy of University Leicester’s Flickr Page – Creative Commons License

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