Pluto’s Naming Game

New Horizons is about to discover a mess of new planetary features. What will we call them?

"Hades; Persephone in the Underworld (Offering to Proserpine)" by Felice Giani, ca. 1820. The dwarf planet is named after Pluto, Roman god of the underworld, who is seated in the middle on the platform at the right; names for newly discovered planetary features will likely follow this theme.

After the New Horizons spacecraft zooms past Pluto on July 14, high-definition images of the dwarf planet’s surface will be available worldwide. But who gets ultimate responsibility for naming its craters and other features? The International Astronomical Union’s Working Group for Planetary System Nomenclature (WGPSN) – the official designator for astronomy names – is asking scientists and the public for ideas related to themes such as the underworld and prominent Pluto scientists.

Working Group chair Rita Schulz answered e-mail questions from Air & Space about how the naming process works. This interview has been edited and condensed.

Air & Space: It’s not often that we visit a new world with few known features (Vesta, Ceres, Comet 67P/Churyumov–Gerasimenko are recent examples). What’s the priority for what features get named first? How are the names allocated, and how quickly does it happen?

Schulz: A feature on a planet, dwarf planet, moon, or asteroid is named every time there is a scientific reason for it. (Please note that the features on comets, such as 67P, do not receive official names, because these are non-permanent features.) This is mostly the case if a scientific paper is written about one or a number of features that have not received a name yet. For instance, we receive on a regular basis requests for naming features on Mars—several dozen a year. Therefore, in that sense, there is not really a priority scale. A feature simply gets named when this is scientifically required.

If a space mission visits a body for the first time, which is the case for the Dawn mission at Vesta and Ceres, or the New Horizons mission at Pluto and its satellites, many features need to be named at once, and it is the scientists who decide which features need to be named. The IAU WGPSN makes sure that the procedure that eventually leads to approved names is in line with the rules for naming such features.

To have some order in the naming, there are certain designated themes. When these themes are established and approved, the approval of the names usually goes rather fast (two to three weeks). Different types of features on a body (e.g. craters, mare, etc.) receive different themes. There also is a different set of themes for each body (e.g., Mars has different themes than Venus).

For example, the Dawn team and the WGPSN have been working closely together in defining the themes for Vesta and Ceres. It was particularly important that the agreed themes guaranteed a large enough pool of names that are sufficiently international, meaning that people all around the world feel addressed/engaged.

Then the Dawn team and the WGPSN established “name banks” for each theme, for which each name is reviewed thoroughly before being approved. When this is finalized, the major part of the work is done and the Dawn team (or another scientist writing a paper about a certain unnamed feature) can request names for the features from the bank. This ensures the approval process goes very fast....

The New Horizons Team will be suggesting names to the IAU, and the WGPSN will decide on which of these names can be approved. How the New Horizons team compiles its list of names to be submitted to the IAU is their affair. Usually, we work closely together with the space mission teams to establish the name banks.

Beside the recent campaign where a few craters were named on Mercury and an exoworlds contest, is this the first time the IAU has opened up naming to the public? Why did you?

The first time the public was involved in choosing names was when the two small satellites of Pluto (P4 and P5), which are now called Kerberos and Styx, were named in 2013. The public has in recent years gotten more and more excited about our planetary system, and also about the fact that there are so many exoplanets around other stars.

The IAU does not only have the mandate to serve the scientific community of astrophysicists and planetary scientists, but is also there to show to “the men and women on the road” how exciting science can be. Involving the interested public in the naming of celestial bodies is therefore an excellent opportunity to engage the public and raise their interest in science.

How much influence does the public have in the naming? SETI, for example, is promoting a campaign to encourage the public to offer suggestions; it has published guidelines and a list of the popular ideas.

One of the New Horizons team members is Mark Showalter, who works at the SETI Institute. I believe that this is the reason the New Horizons team decided to have the public naming campaign coordinated by Mark, via the SETI webpage. The SETI Institute has no particular influence on the naming process. As said already, the NH team is free to decide which names they submit to the IAU for review.

Unfortunately, [the SETI Institute guidelines have] a few shortcomings, in that the IAU rules have not appropriately been explained or referred to. For example, the IAU-approved themes were not mentioned properly, but somehow mixed up.

In order to be eligible for approval, any name suggested by the public (or a scientist) has to be in line with the established rules of the IAU-WGPSN. The IAU has published a press release addressing this subject and the approved themes. Later there was a joint NASA-IAU press release on this topic.

We’ve noticed some informal names coming out as Pluto gets closer (whale, donut, etc.). Would you imagine these names might be kept permanently?

It is common practice that space mission teams use nicknames for features. Such names are always only nicknames, and do not make it into an approved name bank.

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