Who names an asteroid?

When astronomers first spot a new object in the sky, it gets a provisional ‘starter’ name that begins with the year the object was first spotted, followed by at least two upper-case letters to denote which part of the year it was found.

The first letter is A through Y for the half-month of its discovery (skipping ‘I’ and ‘Z’ to give 24 letters). The second letter, A through Z (skipping ‘I’ again), accounts for the order in which the object was found during that half-month.

However, since thousands of objects can be discovered at a time, astronomers added subscript numbers at the end of the name. Once they reach the 26th discovery, they flip back to A and add a subscript 1. The 51st discovery gets an A with a subscript 2, the 101st discovery has a subscript 3, and so on. For example, asteroid 2015 BH568, discovered in the second half of January 2015, was the 14,208th object found in that half-month.

The different parts of an asteroid’s provisional name and what they mean. Credit: Scott Sutherland. Background image courtesy NASA

With the provisional name 2002 VE68, Venus’ odd quasi-moon was the 1,705th asteroid discovered in the first half of November 2002.

This system works well for cataloguing large numbers of objects, giving an astronomer key information about the asteroid just by glancing at its name. It’s a bit clunky when these celestial objects make the news, though.

Fortunately, once an asteroid has been studied sufficiently, the astronomer who found it can request an official final name.