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Reged: 12/04/08
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Neptune new
      #3498841 - 12/13/09 09:33 AM

Today, on the NASA "photo of the day" site is a photo of Neptune and Triton taken by Voyager 2. It's pretty interesting, but it's the caption is more interesting: It says that Neptune "emits more light than it receives from the Sun". How can the be???

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Reged: 02/25/09
Posts: 7662
Loc: 55.215N 6.554W
Re: Neptune new [Re: cloudmagnet]
      #3498882 - 12/13/09 10:05 AM


Neptune "emits more light than it receives from the Sun". How can the be?

"Light" is misleading to a large extent, they mean total radiation - most of the excess is infra-red, and comes from (presumably) radioactive decay of long half life isotopes in the orginal material - the same heat source which keeps the interior of the Earth warmer than its surface. The giant planets may also still be contracting slightly as the internal constituents get "sorted" by convection, the resulting release of gravitational (potential) energy also warms the planet.

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super member

Reged: 03/10/06
Posts: 119
Re: Neptune new [Re: brianb11213]
      #5797738 - 04/14/13 12:41 AM

Perloined from the Encyclopedia Brittanica:

"The temperature of Neptune’s atmosphere varies with altitude...Temperatures also increase with increasing depth below the 0.1-bar level to about 7,000 K (12,000 °F, 6,700 °C) near the centre of the planet, where the pressure may reach five megabars. The total amount of energy radiated by Neptune is equivalent to that of a nonreflecting sphere of the same size with a uniform temperature of 59.3 K (−353 °F, −214 °C). This temperature is called the effective temperature.

Neptune is more than 50 percent farther from the Sun than is Uranus and so receives less than half the sunlight of the latter. Yet the effective temperatures of these two giant planets are nearly equal. Uranus and Neptune each reflect—and hence also must absorb—about the same proportion of the sunlight that reaches them. As a result of processes not fully understood, Neptune emits more than twice the energy that it receives from the Sun. The added energy is generated in Neptune’s interior..."

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Rick Woods

Reged: 01/27/05
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Re: Neptune new [Re: DHurst]
      #5797758 - 04/14/13 01:18 AM

"...but Triton is not for Man."

- Rick
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"The four points of the compass be logic, knowledge, wisdom, and the unknown. Some do bow in that final direction. Others advance upon it. To bow before the one is to lose sight of the three."

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Reged: 01/17/09
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Re: Neptune [Re: Rick Woods]
      #5803411 - 04/16/13 07:20 PM

I do live its enigmatic glint when it shows Rick.



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