Critical-list minor planet

A critical-list minor planet (critical list numbered object or critical object) is a numbered minor planet for which existing measurements of the orbit and position are especially in need of improvement.^[1]

The IAU's Minor Planet Center (MPC) regularly publishes a list of these critical objects in their Minor Planet Electronic Circular.^[2] 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.^[3] The MPC also lists currently observable critical objects on their website,^[4] providing differently formatted lists of orbital elements to the worldwide astrometric community.^[5]

Lowell Observatory publishes their own critical list, distinctly different from the MPC, instead focusing on objects with high ephemeris uncertainty. Specifically, objects with computed ephemeris uncertainty greater than 2 arcseconds over the next 10 years, and objects whose orbits degrade significantly when temporally isolated observations are ignored, are included in the list.^[3]

As of August 2023^[update], the MPC includes 1,494 objects in their critical list. This list contains all critical objects within the first 50,000 numbered minor planets:^[6]

• Distant minor planet
• Lost minor planet
• Unusual minor planet

• MPEC 1998-G21 : CRITICAL-LIST MINOR PLANETS, Minor Planet Circular (1998)
• Asteroid orbit determination using Bayesian probabilities, Karri Muinonen, Edward Bowell (1993)