A Planet by any other Name…is better than a Phone Number


Which would you prefer to hear about: the planet CoRoT-3-b or the planet Cratos?
Since the discovery of the first exoplanet, they have been designated in a rather dreary scientific manner (either by the name of their parent star, such as 51 Pegasi b, or by the telescope that discovered it, such as CoRoT-3-b).  This is a perfectly normal scientific practice: stars and galaxies are designated in a similar fashion (affectionately known by astronomers as “their telephone number”).  But they are also given a more expressive moniker: the Sombrero Galaxy, Sirius, Andromeda, Altair, Eris.  They give a taste of history: with each naming a little piece is added to the cultural jigsaw.

Names are wonderfully evocative: how much of Pluto’s fan club is to do with its association with the cartoon dog (not the Greek God of the Underworld)? This paper argues:

All astronomical bodies are named…why not the exoplanets?

Quite right, I would say.  There is no suggestion of getting rid of the telephone numbers – there’s no reason why Aldebaran and HD 29139 should be mutually exclusive as titles.  Also, the paper argues (quite correctly) that not naming the exoplanets is a form of Copernicanism (i.e. anthropocentric hubris).  For centuries, it has been central to scientific doctrine that we are not special (or at least, there is no evidence to support our uniqueness).  To name our Solar System and no others places us too close to the centre of the Universe.

But how to name such a collection? To date there are 403 exoplanets on record: to name so many requires a naming convention.  Wikipedia spews forth hundreds of naming conventions for planets, satellites and their surface features (from Celtic, Norse, Roman mythologies and even Shakespeare).  The paper suggests a similar convention: look at the constellation the planet lies in, and use its name (and its place in Greek or other mythology) as inspiration.  For example, 51 Pegasi b (the first exoplanet orbiting a Sunlike star) resides in Pegasus, the great winged horse who was tamed by the great prince Bellerophon, a much more artistic title!  Read the paper to find the 402 others (a Herculean effort, if you’ll forgive the pun).

Sadly, there is a rather ugly scientific truth burdening such poetic wings: we’re still at an impasse as to whether a “planet” is actually a planet: the author notes

some of the candidates assigned names here may as well be just low luminosity stars, brown dwarfs, a stellar spot or, as noted by a member of the commission, even a mote of dust in the spectrograph.

Worse still, a rocky body might not be a planet: the so-called “rogue planets” found floating through space without a star to orbit are no longer planets in the conventional sense, but “sub-brown dwarfs” – brown dwarf are the lowest mass stars that exist, so sub-brown dwarfs are even lower mass objects (I presume).  Also, if it’s not big enough to clean up its local neighbourhood of detritus (like Pluto), then it will be demoted to dwarf planet status.

The field is getting more complicated each year, but the aesthetic level, I would argue, despite many artist’s impressions of the exoplanets, has not improved much.  Isn’t it strange that a name (Stygne) is worth a thousand artist’s impressions?

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