Walking home from work along Lyndhurst Road west bound, by the Hospital, my girlfriend and I noticed a middle-bright golden orb, bright white on the outer edge immediately in front of our visual path. There was no wind and the sky very clear of clouds. The orb moved south at a constant speed and path, faster than that of a light-aircraft, but slower than that of a jet. No noise, no flashing lights or emanations. To the north, there was a light aircraft of which I assume was flying towards Shoreham Airport, this was obviously different to the orb as there were very clear lights, some of which strobing. This is when I realised this was definitely not an aircraft that I know of. The orb continued south at the same pace and altitude until it was over the sea where it changed direction at an abrupt angle, continuing south-west, along the Worthing coast line. The light intensity didn't change at any point. Finally the orb changed to a more southerly direction and we observed it until it was too small to see any more. Several other witnesses were watching the orb, looking about as confused as us. This took about 15 minutes from initial observation to the object being invisible to the naked eye.