The Oort Cloud: Made of Comets, Has Massive Diameter
Not only fun to spell, fun to say as well! Oort. Not too many words begin with more than one o! The Oort Cloud is named after Dutch astronomer Jan Hendrik Oort.
In 1950 Oort speculated that the Solar System was surrounded by a vast spherical cloud of comets. He thought this would explain why we still see comets today. He figured that since comets are comprised primarily of water, ammonia, and methane they are extremely volatile and would not last long orbiting the sun. For anyone who has ever seen the long tail of a comet (which is the comet material being blown away by the sun) you know what he was thinking about! There had to be a reserve of them out beyond the direct gravitational pull of the individual planets and even the sun itself. In fact, the Oort Cloud defines the end of the sun’s gravitational influence.
The Oort Cloud was most likely formed as part of the original protoplanetary disk which became our solar system. It is almost a light year distant from the Sun which would put it almost one quarter of the way to the nearest star to us, Proxima Centauri.
Although no one has directly observed the Oort Cloud, it is believed to contain billions of icy cometary bodies. These icy bodies will occasionally be influenced by the gravity of a distant, passing star and become a comet.