(ORDO NEWS) — Using infrared telescopes, scientists tracked the change of seasons on Neptune, which turned out to be significantly different from the earth. The South Pole, which used to be the warmest place on the planet, cooled noticeably with the onset of summer.
Infrared images of Neptune taken with the VLT (2006-2018) and Subaru (2020) telescopes. The bright spot at the bottom of the disk is the south pole
Neptune, the eighth planet in the solar system, receives 900 times less solar heat than Earth, and a year on it lasts 165 Earth years.
According to classical concepts, Neptune has significant reserves of internal heat, and the power of the heat flux coming from the bowels of the planet is one and a half times higher than solar heating.
However, Neptune and the Earth have something in common. The inclination of the Neptunian axis to the plane of its orbit is 28.3 degrees (against 23.5 degrees for the Earth), and seasonal changes in the length of the day and the height of the Sun above the horizon are similar to those on Earth.
The predominance of internal heat over solar heating means that the latter should not significantly affect atmospheric processes. Indeed, on Neptune, the strongest winds in the solar system rage, which are difficult to explain by solar heating alone.
The atmosphere of this planet is very dynamic and changeable : some vortices live for several years, while other cloud systems appear and disappear within a few days.
Infrared images showing the dynamics of cloud systems on Neptune / © Edward Molter & Imke de Pater (UC Berkeley) / Carlos Alvarez (Keck Observatory) / Keck Observatory
Scientists from the Jet Propulsion Institute (JPL), led by Glenn Orton, have analyzed a series of infrared images of Neptune taken with the VLT’s eight-meter telescope and other observatories over the past 19 years. And they found that the seasonal variability of the atmosphere on Neptune still takes place.
Moreover, seasonal changes turned out to be quite dramatic and unlike earthly ones. (Original article and more details can be found here )
In 2005, summer began in the southern hemisphere of Neptune, which will last 40 Earth years. Since the atmosphere of the eighth planet has a large thermal inertia and is heated mainly from below, and not by the Sun, this should have caused only a slight and delayed rise in temperature. Instead, the scientists found significant changes in the Neptunian stratosphere.
At the south pole, from 2018 to 2020, it got warmer by 11 degrees, while the equatorial, tropical and “temperate” regions, on the contrary, cooled down.
The equatorial cooling outweighed the polar warming and was so strong that the average temperature of the stratosphere throughout the planet dropped by six to eight degrees with the onset of summer.
Latitudinal temperature distribution in Neptune’s atmosphere at the tropopause level (100 millibars) from 2003 to 2020. Horizontal latitude (-90 – south pole), vertical temperature in kelvins. The shaded areas are the errors of the given values
Seasonal changes in the deeper layers of the atmosphere also turned out to be unlike those on Earth. In the upper troposphere of Neptune (at the level of 100 millibars, or 0.1 of the earth’s atmosphere), the temperature of the equatorial and tropical latitudes increased from 49-54 to 52-57 kelvins with the onset of summer (from -224 … -219 to -221 … 216 degrees Celsius).
At the pole, on the contrary, it fell from 60 to 52 kelvins (from -213 to -221 degrees Celsius). If in 2003-2010 the south pole of Neptune was the warmest place on the planet, then by 2020 this title has passed to the belt near the southern tropic.
We are talking about rather rarefied layers of the Neptunian atmosphere, and an attempt to draw an analogy with a more familiar world will be strained. But imagine that in the spring and early summer in Murmansk and Svalbard stable average daily temperatures of plus 35 would be kept, and in mid-July a frost suddenly hit.
We note, following the authors of the study, that the calculation of temperature based on the observed data was rather complicated. Scientists determined the temperature based on the intensity of Neptune’s radiation in various parts of the thermal infrared range.
Emissivity is affected by the concentrations of atmospheric impurity gases such as methane, ethane and acetylene, which are also subject to change and difficult to measure accurately. Therefore, the values given in the article have some error.
Nevertheless, from the results obtained, it can already be concluded that seasonal changes in the atmosphere of Neptune are present and radically different from those on Earth. And the dynamics of the atmospheres of gas giants requires further study.
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