provisional designation

Provisional designation systems have been devised to provide immediate labels for objects that have just been discovered, allowing time to consider their eventual permanent names. Distant objects can be immediately labeled by their position on the celestial sphere, but for newly-discovered solar system objects (e.g., minor planets), a designation independent of position is necessary to accommodate observed objects seen at different locations and times that are theorized to be the same object in an orbit. A survey-based designator is often used, but general systems have also been adopted that are based upon the date and order of discovery (or order of report of the discovery). Such a system is needed because of the huge number of candidates discovered, whose observation-data must be tracked while follow-ups help rule out known objects and provide data to reliably identify the same object in the future. The format for (solar system) minor planets:

DDDD AAnumber

• DDDD - four-digit year.
• AA - 2 letters, skipping the letter "I". The first letter indicates the half-month, days 1-15 being the first half (i.e., A for January 1-15, B for January 16-31, etc.), the second letter indicating the order of discovery, A for the first, B for the second, etc.
• number: if more than 25 objects are discovered, a 2 or higher integer indicates the 2nd letter has begun again at "A". E.g., the 26th object is given an A subscripted by a 2, the 27th, a B₂, etc.

Example: 2016 EK₁₅₆

• 2016 - year of discovery.
• E - discovered within March 1-15.
• K₁₅₆ - 3910th object discovered in that period, i.e., K for 10th discovery after 25 × 156 previous discoveries.

Permanent numbers are assigned to minor planets when their orbit has been reliably established (to certain criteria), which is now generally before are given any permanent name. Permanent number 1 was assigned to the first asteroid discovered (Ceres) and numbering currently proceeds by assigning the number following the previously highest assigned number. The term numbered object refers to a minor planet that has received such a number.

For comets, a naming system is used that is different in detail, but also based on the year. Note that it may not be clear whether the object is a comet, and subsequent observation may change the determination, motivating an additional designation.