Contrail

Contrail , a well know phenomena is short for "condensation trails"or vapour trail are long, thin artificial clouds that sometimes form behind aircraft. Their formation is most often triggered by the water vapor in the exhaust of aircraft engines, but can also be triggered by changes in air pressure in wingtip vortices or in the air over the entire wing surface. Contrails are made of water in the form of a suspansion of billions of liquid droplets or ice crystals.

Depending on the temperature and humidity at the altitude the contrails form, they may be visible for only a few seconds or minutes, or may persist for hours and spread to be several miles wide. The resulting cloud forms may resemble cirrus, cirrocumulus, or cirrostratus, and are sometimes called cirrus aviaticus.

The main products of hydrocarbon fuel combustion are carbon dioxide and water vapor. At high altitudes this water vapor emerges into a cold environment, and the local increase in water vapor can raise the relative humidity of the air pastsaturation point. The vapor then condenses into tiny water droplets which freeze if the temperature is low enough. These millions of tiny water droplets and/or ice crystals form the contrails.

Here are some pictures showing contrail & with its formation source  from the Gurudev Observatory. Pictures are taken by Sony Handy cam & without use of telescope.

Gallery of pictures

Video