Name the Exoworlds

Here's your chance to name an exoplanet, in a process recognized and officiated by the International Astronomical Union. Register your astronomy club or organization by June 1st!

Hot Jupiter

Artist's illustration of a hot Jupiter closely orbiting its host star.
C. Carreau / ESA

Astronomers have discovered thousands of exoplanets, but their names, such as HD104985 b, are often in an unfriendly telephone number format. Others, such as 51 Pegasi b, are slightly better, but still not appealing to the general public, nor enticing to the imagination.

For millennia, every civilization across the globe has given names to stars. In ancient days, only those stars that could be seen by the naked eye were named, but after the invention of telescope, the number of known stars increased exponentially. Astronomers developed schemes to catalog them and provide a scientific destination. Take 55 Cancri, the 55th star in the constellation Cancer (the Crab), ordered from west to east using the Flamsteed designation. Using the simpler Bayer designation gives another star the name Epsilon Eridani, because it’s the 5th brightest star (and epsilon is the 5th letter in the Greek alphabet) in the constellation Eridanus (the River).

The International Astronomical Union (IAU) was founded in 1919, and since then has served as the internationally recognized authority for assigning names to celestial bodies such as planets, comets, asteroids. For a long time, those decisions rested on the objects’ discoverers and on the IAU nomenclature committees.

Historically, IAU has not dealt with common names, only with official designations. But now, in response to the public’s increased interest in being part of astronomical discoveries, the IAU is organizing a worldwide contest: “NameExoWorlds” will give popular names to 20 exoplanet systems, including 32 exoplanets along with their host stars.

Here are the 20 systems up for naming:

Host Star (catalog name) Planet designation Planet Mass (Jupiter masses) Planet Mass (Earth masses) Period (days) Semi-major Axis (a.u.) Discovery (year) Constellation (Greek) Host star visible mag.
1 exoplanet (5 systems)
Ain (epsilon Tauri) epsilon Tauri b 7.6 2415.5 594.9 1.93 2007 Taurus 3.5
Edasich (iota Draconis) iota Draconis b 8.82 2803.3 510.7 1.275 2002 Draco 3.3
Errai (gamma Cephei) gamma Cephei b 1.85 588 903.3 2.05 2003 Cepheus 3.2
Fomalhaut (alpha Piscis Austrini) Fomalhaut b 3 953.5 320000 115 2008 Piscis Austrinus 1.2
Pollux (beta Geminorum) beta Geminorum b 2.9 921.7 589.64 1.69 2006 Gemini 1.2
1 star + 1 exoplanet (10 systems)
14 Andromedae 14 Andromedae b 5.33 1694 185.84 0.83 2008 Andromeda 5.2
18 Delphinis 18 Delphinis b 10.3 3273.6 993.3 2.6 2008 Delphinus 5.5
42 Draconis 42 Draconis b 3.88 1233.2 479.1 1.19 2008 Draco 4.8
51 Pegasi 51 Pegasi b 0.47 148.7 4.23 0.052 1995 Pegasus 5.5
epsilon Eridani epsilon Eridani b 1.55 492.6 2502 3.39 2000 Eridanus 3.7
HD 104985 HD 104985 b 6.3 2002.3 198.2 0.78 2003 Camelopardalis 5.8
HD 149026 HD 149026 b 0.36 113.1 2.88 0.04288 2005 Hercules 8.2
HD 81688 HD 81688 b 2.7 858.1 184.02 0.81 2008 Ursa Major 5.4
tau Bootis tau Bootis b 5.9 1875.2 3.31 0.046 1996 Boötes 4.5
xi Aquilae xi Aquilae b 2.8 889.9 136.75 0.68 2008 Aquila 4.7
1 star + 2 exoplanets (1 system)
47 Ursae Majoris 47 Ursae Majoris b 2.53 804.1 1078 2.1 1996 Ursa Major 5.1
47 Ursae Majoris c 0.54 171.6 2391 3.6 2001 Ursa Major 5.1
1 star + 3 exoplanets (2 systems)
PSR 1257+12 PSR 1257+12 b 7.00E-05 0.022 25.26 0.19 1992 Virgo -
PSR 1257+12 c 0.01 4.1 66.54 0.36 1992 Virgo -
PSR 1257+12 d 0.01 3.8 98.21 0.46 1992 Virgo -
upsilon Andromedae upsilon Andromedae b 0.62 197.1 4.62 0.059 1996 Andromeda 4.1
upsilon Andromedae c 1.8 572.1 237.7 0.861 1999 Andromeda 4.1
upsilon Andromedae d 10.19 3238.7 1302.61 2.55 1999 Andromeda 4.1
1 star + 4 exoplanets (1 system)
mu Arae mu Arae b 1.68 532.7 643.25 1.5 2000 Ara 5.2
mu Arae c 0.03 10.6 9.64 0.09094 2004 Ara 5.2
mu Arae d 0.52 165.9 310.55 0.921 2004 Ara 5.2
mu Arae e 1.81 576.5 4205.8 5.235 2006 Ara 5.2
1 star + 5 exoplanets (1 system)
55 Cancri 55 Cancri b 0.8 254.3 14.65 0.1134 1996 Cancer 6
55 Cancri c 0.17 53.7 44.34 0.2403 2002 Cancer 6
55 Cancri d 3.84 1218.9 5218 5.76 2002 Cancer 6
55 Cancri e 0.03 8.3 0.74 0.0170 2004 Cancer 6
55 Cancri f 0.14 45.8 260.7 0.781 2007 Cancer 6

Registered organizations voted for these 20 systems during an earlier stage of the IAU contest. They are a diverse set of systems, many of them significant in the history of exoplanet research. The list includes the first exoplanet ever discovered, orbiting the pulsar PSR 1257+12, the first exoplanet discovered around a normal star, 51 Pegasi b, and the five-exoplanet system 55 Cancri.

Fomalhaut b

An artist's illustration of the controversial exoplanet Fomalhaut b. The planet might be sweeping out the edge of a massive ring of dust around the young star.
ESA / NASA / L. Calcada

Other systems tell fascinating stories: the planets of Upsilon Andromedae orbit on different planes, suggesting a possible past encounter with a rogue planet later ejected from the system. Another planet, Fomalhaut b, was imaged at visible wavelengths (a difficult feat) orbiting at the edge of the star’s dusty debris disk.

To submit names, you’ll have to go through an organization registered on the IAU Directory of World Astronomy website. Each registered organization can submit one naming proposal. To qualify, organizations must be non-profit and have organized one astronomy-related activity, a broad definition that enables schools to register too.

If your local astronomy club or other organization is interested in registering, the deadline isn’t over yet. Organizations can register with the IAU until June 1st. This is a golden opportunity to educate the general public on the science of exoplanets as well as the history and culture behind these astronomical discoveries.

Name submissions should follow IAU guidelines — for example, you can’t name a planet after your pet or any living person. As part of your submission, you’ll include a description to justify your proposal.

All of the submitted names will be open for a massive public voting to decide on the final names. The key to success rests on proposing names for the planets that can garner worldwide support.

The deadline for organizations to register with IAU for name submissions is 8 p.m. (EDT) on June 1st. Names themselves can be submitted until 8 p.m. (EDT) on June 15th. Check out the Name Exoworlds website for more details.


Sze-leung Cheung is the IAU International Outreach Coordiantor and heads the IAU Office for Astronomy Outreach, a global office for coordinating worldwide astronomy outreach activities. He was one of the key people behind the NameExoWorlds campaign.

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