Neptune heat source

Earth-based infrared observations of Neptune indicated by 1974 that, unlike Uranus, Neptune emits 2.4 times as much energy at infrared wavelengths as it receives frc n sunlight (insolation). This led to the infer-erKe that, like Jupiter and Saturn, Neptune has a significant internal heat source. This may be produced by cc i-... 

The temperature at the aerosol layer in Neptune s atmosphere is about -346°F (-210°C), which is close to the temperature at the main cloud level in Uranus s atmosphere, and the effective temperatures of the atmospheres of both Uranus and Neptune were found to be close to this temperature. One would expect Neptune s visible troposphere and lower stratosphere to be about 59°F (15°C) colder than those of Uranus because of Neptune s greater distance form the Sun (30.1 a.u. vs. 19.2 a.u.) instead, the temperatures of these parts of the atmospheres of both planets are found to be about the same. Neptune s atmosphere seems to be considerably warmer than it would be if it received all or nearly all its heating from sunlight, as seems to be the case for Uranus. This is another indication that Neptune has a powerful internal heat source, unlike Uranus, which has at most a weak internal heat source (compatible with radioactivity in its interior) or none at all. Voyager 2 infrared observations confirmed this the emission to insolation ratio was found to be 2.6 from them instead of... 

According to Figs. 8.2.2 and 9.1.1, a greenhouse effect appears to exist for all planets with substantial atmospheres, although in the cases of Jupiter, Saturn, and Neptune the effect is overwhelmed at very large depths by an internal heat source. This heat source leads to dynamically active lower tropospheres in these major planets, a subject discussed in the next section. 

Neptune has about the same surface temperature as Uranus though it is at a greater distance to the Sun. This can be explained by an internal heat source. Neptune radiates 2.6 times as mueh energy as it receives from the Sun. The sources for its internal heating are unknown but several processes have been proposed such as radiogenic heating from its core, dissociation of methane into hydrocarbon chains, convection in the lower atmosphere. 

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