Learn what exoplanet names were chosen for 14 stars & 31 exoplanets that orbit them by the International Astronomical Union based on a popular contest!

This is the time of year when we often hear advertisements from companies that offer to name a star after one of your friends or loved ones — for a price, of course.

But these personalized monikers aren't as official as the promoters would like you to believe. In fact, for decades the International Astronomical Union has insisted that it, alone, is the recognized authority for naming stars. The star names we're used to (Aldebaran, Betelgeuse, Polaris) and even obscure ones (Cursa, Grumium, Zavijava) predominantly come from a listing of hundreds of stars — often with multiple or conflicting names — in the Yale Bright Star Catalogue, which the IAU embraced long ago.

One flaw in the IAU's proprietary claim is that this august organization has never, in its century of existence, actually bestowed a common name on a star — until last week.

A high-level IAU panel, dubbed the Executive Committee Working Group on the Public Naming of Planets and Planetary Satellites, has announced that 14 stars and 31 exoplanets are receiving officially recognized names.

Artist rendering of 42 Draconis, one out of many examples of exoplanet names.
The planet 42 Draconis b, discovered in 2008 and rendered here by an artist, has 1,233 times Earth's mass and orbits its host star in 479 days. The International Astronomical Union has formally named this planet Orbitar, and its star is now named Fafnir.

These (and many others star and exoplanet names) had been proposed by amateur astronomers earlier this year as part of the IAU's Name the Exoworlds contest. A public vote followed, and by the time the polling closed on October 31st stellaphiles from 182 countries had cast 573,242 votes on exoplanet names.

Five of the planets' host stars already had common names, but in most cases they did not. So the working group decided to name both stars and planets. (Problems arose with naming Tau Boötis, one of the 20 candidate systems, so the IAU panel will revisit that one at a later date.)

Up to this point, astronomers simply assigned an alphabet letter to any planet discovered around a distant star. So, for example, a Jupiter-size world discovered around 51 Pegasi in 1995 became known as 51 Pegasi b — a functional but uninspiring name for the first planet found around a solar-type star. Now we can start calling it "Dimidium." That's Latin for "half," a reference to the fact that it's at least half the mass of Jupiter. And the star itself is now called "Helvetios," derived from a Celtic tribe that once inhabited Switzerland.

Here's the new set of exoplanet names, along with a link to the amateur group that proposed it. Some notables include the confirmed exoplanets surrounding pulsar PSR 1257+12 (the first ones discovered, way back in 1992) and the five-planet system of 55 Cancri (now Copernicus). (For the derivations of the names, see the detailed table on this page.)

New Set of Exoplanet Names:

New IAU Star and Exoplanet Names
Star name Designation Planet name Designation Submitter
Veritate* 14 Andromedae Spe* 14 Andromedae b Canada
Musica 18 Delphini Arion 18 Delphini b Japan
Fafnir 42 Draconis Orbitar 42 Draconis b U.S.
Chalawan 47 Ursae Majoris Taphao Thong 47 Ursae Majoris b Thailand
Taphao Kaew 47 Ursae Majoris c
Helvetios 51 Pegasi Dimidium 51 Pegasi b Switzerland
Copernicus 55 Cancri Galileo 55 Cancri b The Netherlands
Brahe 55 Cancri c
Lippershey 55 Cancri d
Janssen 55 Cancri e
Harriot 55 Cancri f
(Ain) Epsilon Tauri Amateru* Epsilon Tauri b Japan
Ran* Epsilon Eridani AEgir* Epsilon Eridani b U.S.
(Errai) Gamma Cephei Tadmor* Gamma Cephei b Syria
(Fomalhaut) Alpha Piscis Austrinus Dagon Alpha Piscis Austrinus b U.S.
Tonatiuh HD 104985 Meztli HD 104985 b Mexico
Ogma* HD 149026 Smertrios HD 149026 b France
Intercrus HD 81688 Arkas HD 81688 b Japan
Cervantes Mu Arae Quixote Mu Arae b Spain
Dulcinea Mu Arae c
Rocinante Mu Arae d
Sancho Mu Arae e
(Pollux) Beta Geminorum Thestias* Beta Geminorum b Australia
Lich PSR 1257+12 Draugr PSR 1257+12 b Italy
Poltergeist PSR 1257+12 c
Phobetor PSR 1257+12 d
Titawin Upsilon Andromedae Saffar Upsilon Andromedae b Morocco
Samh Upsilon Andromedae c
Majriti Upsilon Andromedae d
Libertas* Xi Aquilae Fortitudo* Xi Aquilae b Japan
(Edasich) Iota Draconis Hypatia Iota Draconis b Spain

* These names are modified from the original proposals to be consistent with IAU rules. Common star names in parentheses existed previously.

IAU Finally Enters the Fray

Actually, IAU astronomers have been assigning coordinate-infused stellar designations for decades, via its Working Group Designations. "What the WGD focuses on is assuring that newly created catalog names have a nomenclature that is unique and follows a few detailed guidelines," explains Marion Schmitz (Caltech), its current chair. "These often make up what has been referred to as 'the boring numbers.' However, in the big picture of all multi-wavelength and multi-object astronomy, uniqueness in nomenclature is essential. We try not to get involved with what common usage determines to be the popular name for an object."

Planet around Epsilon Eridani
An artist's impression of a planet and dust rings surrounding the nearby Sun-like star Epsilon Eridani. Thanks to the IAU, the star is now called Ran and its planet AEgir.

In fact, I encountered this same "hands-off" approach some 15 years ago. That's when I asked IAU officials why they hadn't assigned a common name for Epsilon Eridani, a solar-type star easily seen by the naked eye (magnitude 3.7) and only 10.5 light-years away (making it the ninth-closest star). Not only did Epsilon Eridani have a just-discovered planet, I argued, but it also had become famous as one of the two stars targeted in Frank Drake's pioneering Project Ozma in 1960, the first search for intelligent life.

At the time I suggested (to radio astronomer Hélène Dickel, who then chaired the IAU's Task Group on Astronomical Designations) that the IAU set up a Working Group to solicit and approve common names for bright stars that lacked them. To her credit, she circulated my idea to other members of the task group. Here are some of the responses (yep, I kept all the emails):

"The name of the star is in fact Epsilon Eridani; it is how it is known to all. To name it otherwise can only lead to confusion . . ."

"I think that name [Epsilon Eridani] is an excellent one, and suits the star admirably."

Not exactly the enthusiastic response I'd hoped for. So, when the Task Group politely declined, the S&T staff even kicked around the idea of running a contest to name Epsilon Eridani. But nothing ever came of it. #KickingSelf #MissedOpportunity

My editorial colleague Roger Sinnott points out that the IAU did approve the name Proxima Centauri, sort of, in The First Dictionary of the Nomenclature of Celestial Objects (Solar System Excluded) by A. Fernandez, M.-C. Lortet, and F. Spite. On page 6.7, Proxima Centauri is listed as another name for Innes' Star. But use of Proxima Centauri appears to predate the IAU's existence, so official naming took place.

Meanwhile, Out on Pluto . . .

The Name the Exoworlds contest isn't the IAU's only current involvement in assigning monikers. Right now there's something of a standoff between its Working Group for Planetary System Nomenclature and scientists involved with NASA's New Horizons mission.

If you read all the press releases carefully, you'll note that all the names being using for features on Pluto and Charon — Tombaugh Regio, Sputnik Planum, even a crater named Skywalker — are "informal." These came about after the mission team, in concert with the IAU, solicited suggestions in a naming campaign called Our Pluto. But here we are five months after the flyby, and not a single name has received official approval. Meanwhile, published scientific papers and other publications have used the names freely.

Informal names on Pluto
Although informal for now, these feature names follow an approved scheme and have been submitted to the IAU for approval.

Publicly, mission leader Alan Stern explains that his small team has simply been too busy analyzing results to submit a formal proposal to the IAU. Rita Schulz, who heads the WGPSN, confirms that her group is still waiting to hear from the New Horizons team.

But there's more to it. Last August, during the IAU's triennial General Assembly, Louise Good and Lars Lindberg Christensen admonished the New Horizons team: "Unfortunately, some of the names used for features on Pluto and Charon fall outside the themes accepted by the IAU." Giovanni Valsecchi, another IAU official, scolded New Horizons scientists for "promulgating nicknames."

International Astronomical Union names for features on Pluto and its satellites
International Astronomical Union

Stern fired back the next day: "The names on our informal Pluto system maps . . . were obtained via an open international naming campaign that the IAU endorsed." And it was very successful, netting 75,000 submissions. However, Stern continues, just before Our Pluto's launch last March, WGPSN requested that the campaign restrict the submissions to "a set of themes primarily focused on death deities and the underworld." He pointedly concludes, "We look forward to collaborating with a Working Group that operates in the open and that recognizes its accountability to both scientists and the broader public."

So stay tuned to see if Cthulhu Regio, Lowell Regio and Spock crater make the eventual cut.


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December 18, 2015 at 5:18 pm

Strange that they are using names already in the literature. Hypatia is also asteroid 238 for example, never mind Copernicus...

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J. Kelly Beatty

December 20, 2015 at 12:00 am

hi... I contacted Theirry Montmerle, who headed the selection committee. He said, "We discussed this case extensively, and in the end we decided to make an exception. The winning argument was that Hypatia deserved more prominence in the sky than an asteroid."

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December 18, 2015 at 7:45 pm

I don't understand this at all. By long standing tradition the discoverer of a new planet has the absolute right to name his discovery. Who gave the IAU the privilege?

Anyway, what's the meaning of some of these names? I can find Epsilon Eridani; I doubt I'll ever remember to call it Ran (or maybe Run). I've known Pollux since I was a kid. Why should anybody think its name could be changed?

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J. Kelly Beatty

December 19, 2015 at 9:38 am

Peter: you make some good points (though Pollux has not been renamed -- Thestias applies to its planet). as far as discoverers naming their planet, recall that Herschel wanted to name Uranus after King George III, which was not a popular idea. I just came across an old textbook from 1830 that listed Uranus as "Herschel", so apparently the matter wasn't completely settle even by then -- a half century after Uranus's discovery! The name "Uranus" was first proposed by German astronomer Johann Elert Bode.

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December 28, 2015 at 11:53 am

This is a wonderfully diverse list. One planet is even named after a garment!

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