* No defined edge: The Oort cloud is not a solid, spherical object. Instead, it's a theoretical region containing icy debris, extending far beyond the orbits of the planets. It gradually thins out, making it difficult to define a clear outer edge.
* Estimated size: Estimates vary, but the Oort cloud is believed to start somewhere around 1,000 AU (astronomical units) from the Sun and extend out to about 100,000 AU. One AU is the average distance between the Earth and the Sun.
* Indirect evidence: Our knowledge of the Oort cloud comes primarily from observing long-period comets that originate from it. This information provides clues about its existence and likely size, but not a precise measurement.
In summary, the Oort cloud is an immense and hypothetical region, and its diameter remains an ongoing area of scientific study.
