Minor planet designation: numbering and naming of small Solar System bodies

Formal parts of a designation

A permanent minor planet designation typically has two components: a number and a name. The number is allocated after the object's orbit is well determined and appears in front of the name; the name is either a formal name approved by the IAU or, if no formal name exists, the object's provisional designation. Common formats include the parenthesized form, for example (90377) Sedna (Sedna example), and the unparenthesized form 90377 Sedna. If a body has not been given a formal name, the designation will read, for example, (55636) 2002 TX300 or simply 2002 TX300 in ordinary usage.

Provisional designations, numbering, and naming process

When a new object is discovered it receives a provisional designation that encodes the year of discovery and the order within that year (a letter-based scheme). Following additional observations and orbit determination, the MPC assigns a permanent sequence number. After numbering, the discoverer is invited to propose a name that conforms to IAU guidelines; proposed names are reviewed and, if accepted, published with a citation. Many objects remain numbered but unnamed for long periods and are commonly referred to by their number or provisional tag.

1. Discovery and provisional designation (year + code)
2. Follow-up observations and orbit confirmation
3. Assignment of a permanent number by the MPC
4. Proposal, review, and approval of a name by the IAU committee

Moons of minor planets and other special cases

Moons of minor planets are named by extending the Roman numeral convention used for planetary satellites. For example, the moon Romulus of asteroid Sylvia has been referred to as (87) Sylvia I Romulus (satellite designation). Dwarf planets are treated under the same numbering and naming framework as other minor planets (dwarf planet context), while comets use a separate cataloging system and naming conventions maintained historically by the MPC (comet nomenclature).

Usage, distinctions, and notable facts

In practice, the numeric portion mainly serves catalog and database functions; well-known objects are most often cited by their proper names (for example, Ceres, Pallas) or by their provisional designations when no name exists. The IAU maintains guidelines to avoid duplications, overly commercial or offensive names, and excessive similarity to existing names. The numbering-and-naming system helps astronomers, observatories and data centers cross-identify observations, link orbital elements and communicate unambiguously about small bodies across the research community (asteroid studies).

For further procedural details and current lists of numbered and named objects consult the Minor Planet Center resources and related catalogs maintained by astronomical organizations (MPC, example entries, comet distinctions).