Hypothesized as a reason for long-period comets such as Hale-Bopp and Hyakutake, for 10 points, identify this so-called "cloud" past the end of the solar system, named for a Dutch astronomer.
Its outer boundary lies about 30 trillion kilometers from the sun near the heliopause, the theoretical end of the sun's dynamical influence. Although we cannot prove its existence, it was posited by the man who first accurately described the rotation of the Milky Way galaxy in the 1920s. Hypothesized as a reason for long-period comets such as Hale-Bopp and Hyakutake, for 10 points, identify this so-called "cloud" past the end of the solar system, named for a Dutch astronomer.
Its outer boundary lies about 30 trillion kilometers from the sun near the heliopause, the theoretical end of the sun's dynamical influence.
{Öort} Cloud