The Oort Cloud

describe some of the evidence for the existence of the Oort Cloud

Where do long term comets come from?

Their orbits suggest that they originate from a region about 50,000 AU from the Sun ( a thousand times the orbit of Pluto !). They also come from all directions, not just from the same plane like Kuiper belt objects.

In 1950 Jan Oort suggested that there was an enormous spherical cloud surrounding our solar system, now called the Oort cloud. It would extend out into space perhaps to a distance of a light year and contain many millions of objects of different sizes. Again it may be remnants of the early solar system, perhaps the planetary nebula from which our solar system formed.

There is no direct evidence, as yet, for the existence of the Oort cloud.