The IAU's Minor Planet Center (MPC) regularly publishes a list of these critical objects in their Minor Planet Electronic Circular. The list typically contains asteroids that have been observed at a small number of apparitions, especially on opposition, or that have not been adequately observed for more than 10 years, while other observatories create their own, customized lists. The MPC also lists currently observable critical objects on their website, providing differently formatted lists of orbital elements to the worldwide astrometric community.
As of July 2020[update], the MPC includes more than a thousand objects in their critical list, half of them being either near-Earth asteroids or distant minor planets which account for 674 and 192 critical objects, respectively.
The lowest numbered critical-list objects are: