The most distant gas giant in the Solar System

 

By Jeffrey Kasoff, Secretary, Salina Astronomy Club

 

4-Nov-2010

 

The planet Neptune is just completing its first orbit around the sun since its discovery on 23-Sep-1846.  Wow.  Its sidereal orbit period of 164.8 earth years or some 60,000 days puts it in the same star field as when it was first discovered.  The newly refurbished 16” (40cm f/11) Ealing 'Educator' telescope at KWU or even Celestron C-11 quality telescopes should be equal to the task of observing Neptune or re-enacting the planetary discovery!  No need to dress in period Victorian costumes unless you really want to for the re-enactment.  Neptune's current position based on osculating orbital elements is probably accurate to a couple of arc-min, so should be easy to locate on a clear night.  

 

The original discovery instrument was a state of the art telescope for the early 19 ^th century, a 24 cm f/18 Fraunhofer refractor fitted to a prototype German equatorial mount.  See page 8 of 17 of PDF listed below for pic of discovery instrument, a 14 foot long Fraunhofer refractor on display at the Deutsches Museum, Munich, Germany; http://www.fraunhofer.de/en/publications/brochures/joseph_tcm6-42772.pdf.  

 

It took Johann Galle at the Berlin Observatory less than one hour to find the new planet given its position worked out by the French mathematician, Urbain Le Verrier.  Who says the French aren’t smart.  See the following link for more discovery info:  http://en.wikipedia.org/wiki/Discovery_of_Neptune.  The planetary prediction, accurate to one arc-deg from the discovery position, was derived from perturbations in the orbit of Uranus, discovered only 65 years earlier on 13-Mar-1781.  

 

Weather-permitting after SAC's well advertised Skywatch talk on 12-Nov, we should try not only to observe Jupiter, but also Uranus and even Neptune.  Our guests, the public, may not be impressed; but the discovery of these outer gas giants did reinforce a revolution in both Newtonian thinking and modern technology.   

   

For impressive preview pics of Neptune a) captured during Voyager II flyby in 1989, b) from Hubble Space Telescope, and c) from the ground-based Keck Telescope with adaptive optics; follow the link:  http://www.universetoday.com/21642/pictures-of-neptune/.