Return to the Cloudy Nights Telescope Reviews home page


Observing >> Planetary and Solar System Observing

Pages: 1
cloudmagnet
sage


Reged: 12/04/08
Posts: 225
Loc: Georgetown, Texas
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???

--------------------
14" f/4.8 Obsession Clone w/ ServoCat/ArgoNavis
Apogee RA-88 Binocs


Post Extras: Print Post   Remind Me!   Notify Moderator  
brianb11213
Postmaster


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

Quote:

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.

--------------------
I ache, therefore I am


Post Extras: Print Post   Remind Me!   Notify Moderator  
DHurst
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..."

--------------------
No materialistic vanity list to sport.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Rick Woods
Postmaster


Reged: 01/27/05
Posts: 11940
Loc: Inner Solar System
Re: Neptune new [Re: DHurst]
      #5797758 - 04/14/13 01:18 AM

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

--------------------
- Rick
14" LX200
Cactus Patch Observatory

"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."


Post Extras: Print Post   Remind Me!   Notify Moderator  
azure1961p
Postmaster


Reged: 01/17/09
Posts: 6214
Loc: USA
Re: Neptune [Re: Rick Woods]
      #5803411 - 04/16/13 07:20 PM

I do live its enigmatic glint when it shows Rick.

Pete

--------------------

"I got here the same way the coin did" - Anton Chigurh

70mm TV Ranger
150mm SCT, Celestron
8" F/9 PARKS reflector, George Clements Mirror
Plossls, Orthos, TV Barlows
DBK21au

http://www.cloudynights.com/photopost/showgallery.php?ppuser=64701&cat=500


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1


Extra information
0 registered and 9 anonymous users are browsing this forum.

Moderator:  Tom L 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 2320

Jump to

CN Forums Home



Cloudy Nights Sponsor: Astronomics