If you have been reading about exoplanets, you know that they all have boring names, such as GJ 876b, 51 Peg b, or WASP-19b (not to speak about the likes of KOI-762.02). Up to a few days ago the official names of exoplanets had to be the catalog identifier of their host star plus a letter assigned in the order the planet was discovered in the given system. Yes, while most sci-fi writers used exotic names for their planets, astronomers shied away from anything more exciting than GJ 436b. These were the rules – even if you discovered a new planet, you could not give it a proper name!
But this has all changed with a new decision by the International Astronomical Union, the entity that represents astronomers worldwide.
To understand the changes let me tell you more about the background of naming celestial objects and, in particular, extrasolar planets.
Let’s start with stars. All bright stars on the sky have names, often derived from their Arabic names (such as Altair or Deneb). Nowadays these names
are often used by amateur astronomers, but professional astronomers tend to use a simpler scheme: in each constellation the brightest star is named Alpha, the second brightest is Beta, etc. leading to names like alpha Persei (the brightest star of the constellation Perseus). However, most stars that we study are too faint for this system – there are not enough letters in the Greek alphabet to name the 13,234th brightest star in Orion!. We now simply use an identifier from one of the all-sky catalogs of stars. These names look like HD 172555, which is the 172,555th star in the Henry-Draper Catalog, a list of stars and celestial positions compiled in 1924. Similarly, a name like GJ 436 is the 436th star in the catalog of nearby stars compiled by German astronomers Wilhelm Gliese and Hartmut Jahreiss. Because the catalogs have the coordinates of each star, astronomers do not need to know anymore in which constellation it belongs to.
Sounds simple, right? But as astronomers began to study in detail the stars in the catalogs, many of the apparently single stars turned out to be two stars orbiting around each other (more precisely: they really orbit around the center of mass of the system). Of course, once you spent 15 years cataloging around 200,000 stars and numbered them, you don’t want to renumber all of them just because the third star turned out to be a binary, right?
Instead, astronomers decided to make a logical change to the system: if a star turns out to be a binary star, we keep the catalog number, but call the two stellar components as A and B. Some systems even turned out to have four components, leading to letters A through D.
Then came planets and with their discovery another change was needed. You could envision to add numbers for each planet, but astronomers decided that the simplest solution is to use lower-case letters for the planets: GJ436 b, for example, is the first planet discovered around the 436th star of the Gliese-Jahreiss catalog. Why is not planet “a” the first planet? Astronomers thought that “a” could lead to confusion with the star itself, so the planets start from b.
This system was simple and worked well. But as the number of planets rapidly grew and they became frequent subjects of the news in all media, there was more and more pressure to introduce more interesting names. The interest was so high that many companies decided to sell planet names – just as some companies used to sell land on the moon.
Eventually, the IAU decided to allow the public to propose planet names.
This is a welcome decision: Allowing everyone to propose names for new worlds means sharing the excitement of discovery.
So, how do you name your own planet?
Understandably, the IAU wants to proceed carefully and wants to avoid names that are controversial (xkcd collected an interesting set of possibilities). So, there is a somewhat complex submission and approval process, but the key points are that you need to identify a suitable name and gather enough support. The name should be, of course, not offensive and should not aim to lead to any financial or political advantages. The next step is to convince a large number of people to support the proposal and then submit it to the IAU for approval. The process is overall very similar to that used to name minor planets in the Solar System.
With this opportunity open, we will surely see interesting and original planet names popping up in large numbers!