Is the Hubble telescope able to give us real proof of the Oort cloud?
No, it is not. Hubble and many large telescopes on the ground have recently been used to discover and track objects in the Kuiper Belt, which is about 100 astronomical units from the Sun. It is very challenging to observe these objects, since they small, black, and very far away, so they are 25th magnitude and dimmer! Objects in the Oort Cloud, believed to be 100,000 AU from the Sun, would be impossible to observe even with the best telescopes today. So the Oort Cloud can still only be inferred from the orbits of long-period comets.
This page was last updated June 28, 2015.