Question: We cannot see the Oort cloud with any of our technology (i.e. Hubbel or anything else) but we CAN see Kuiper belts around other stars (several magnitudes farther away). Explain? — Tim
Answer: The reason that we cannot see the Oort Cloud around our own Solar System is that it is believed to be 100,000 AU from the Sun and comprised of very small and dark objects which are hard to detect. We infer the existence of the Oort Cloud due to the fact that we observe long-period comets coming from this distance. Kuiper Belts that have been detected around other stars have largely been toward stars that are younger than ours, so that they have more remnant dust and gas around them. This remnant dust and gas forms a “belt” around these young stars, is dense enough to be observable with telescopes that are sensitive to dust which has been heated by its parent star, and appears to have characteristics that we attribute to a young Kuiper Belt around these stars.