Astronomy and Space

Observation and Measurement

How are new celestial objects named?

Many stars and planets have names that date back to antiquity. The International Astronomical Union (IAU), the professional astronomers organization, has attempted, in this century, to standardize names given to newly discovered celestial objects and their surface features.

Stars are generally called by their traditional names, most of which are of Greek, Roman, or Arabic origin. They are also identified by the constellation in which they appear, designated in order of brightness by Greek letters. Thus Sirius is also called alpha Canis Majoris, which means it is the brightest star in the constellation Canis Major. Other stars are called by catalog numbers, which include the star’s coordinates. Several commercial star registries exist, and for a fee you can submit a star name to them. These names are not officially recognized by the IAU.

The IAU has made some recommendations for naming the surface features of the planets and their satellites. For example, features on Mercury are named for composers, poets, and writers; features of Venus for women; and features on Saturn’s moon Mimas for people and places in Arthurian legend.

Comets are named for their discoverers. Newly discovered asteroids are first given a temporary designation consisting of the year of discovery plus two letters. The first letter indicates the half-month of discovery (A = first half of January, B = second half of January, etc.) and the second the order of discovery in that half-month. Thus asteroid 2002EM was the thirteenth (M) asteroid discovered in the first half of March (E) in 2002. After an asteroid’s orbit is determined, it is given a permanent number and its discoverer is given the honor of naming it. Asteroids have been named after such diverse things as mythological figures (Ceres, Vesta), an airline (Swissair), and the Beatles (Lennon, McCartney, Harrison, Starr).


This is a web preview of the "The Handy Science Answer Book" app. Many features only work on your mobile device. If you like what you see, we hope you will consider buying. Get the App