Last night, NASA made a momentous announcement: the discovery of seven potentially-habitable exoplanets—exo, because we still think about the universe as if our solar system were at its centre—circling a star 39.5 light years from the sun.
We call the star Trappist-1. It was discovered with the help of a telescope in the Chilean mountains called TRAPPIST—Transiting Planets and Planetesimals Small Telescope—after a monastic order known for brewing great beers. Trappist beers are made by Trappist-Cistercian monks. What’s the connection? The planets circling Trappist-1 are in what we call a “Goldilocks zone”, a distance from their star that is neither too hot nor too cold to support liquid water, one of the conditions of life. Trappist beers are best between 8 and 10 degrees Celsius.
The planets circling Trappist-1 (known as Trappist-1b to Trappist-1h) were discovered by a team led by Michaël Gillon at the University of Liège in Belgium. They are among 3,583 exoplanets that astronomers have identified since 1992, the year in which the first three were confirmed around the pulsar PSR B1257+12. This is a remarkable achievement. In Churchill’s time, it was doubtful whether there were any planets beyond our solar system. Today, we estimate that there could be as many as 40 billion Earth-sized planets potentially capable of harbouring life in our galaxy. This makes coming up with new names difficult.
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When we named the first celestial bodies, we called them things that related to our lives and beliefs. Groups of stars looked like archers, wolves and ships, so we called them Sagittarius, Lupus and Argo. The Hellenic Hydra shared stars with the Ancient Chinese Vermilion Bird of the South, and Aries with the White Tiger of the West. Someone in Ancient Greece saw an ox-driver in the sky and so we have boötes (literally, an ox-driver), a constellation of several dozen stars in the northern sky. Looking to the planets, we saw features that matched the characteristics and temperaments of mythic gods. We gave them names like Ishtar, Ares or Jupiter.
Most stars and planets today aren’t “named”. They are given catalogue designations, which record information about their locations or the ways in which they were discovered. Trappist-1 is 2MASS J23062928-0502285. Our sun lacks a designation. We often refer to it by the Latin sol.
Features on planets—valleys, mountains, islands, regions, terrains or craters—are given names, too. Mars’s Olympus Mons is over twice the height of our Everest. A region of volcanic craters on Jupiter’s moon Io is called the Tvashtar Paterae, after the Hindu god of blacksmiths. The Conamara Chaos is a region of violent, rugged terrain on Jupiter’s moon Europa. It was named after a region of Ireland and inspired perhaps by a 1993 book about stone rows of Britain, Ireland and Brittany. (That is as much as one can glean from its entry on the Gazetteer of Planetary Nomenclature).
The International Astronomical Union, a society of astronomers, has a set of Rules and Conventions on planetary nomenclature. Names can’t have “political, military or religious significance”, although they can relate to historical figures. Small craters on Mars must be named after small towns and villages on Earth. Every feature on Venus must have a feminine name, although three masculine names predate this convention. The methodology isn’t fool proof—betelgeuse, the brightest star in the Orion constellation, is variously called Alpha Orionis and J05552+0724AP, among other things—but it has given us a standardised, widely used set of identifiers for objects in space.
The conventions become less stringent for smaller bodies. On 13 April 1996, an astronomer at the University of Arizona discovered an asteroid. Spacewatch, an astronomical project that studies small planets, asteroids and comets, later confirmed the finding. Jim Scotti, one of Spacewatch’s members, called it 12818 Tomhanks, in homage to the actor. “Tom Hanks is a fellow space geek,” Scotti said in an interview with Space.com, “he grew up with Apollo and man walking on the moon.” Not long after, another astronomer gave us 8353 Megryan. The two circle around the sun, occasionally crossing paths.
The names for the known, visible world are familiar. The names for the abstract world of deep space are long, alphanumeric designations. There is something poetic about this: as the complexity of our known world increases, so do our systems of classification and description. This is true of all sciences, and especially of physics and astronomy, which must find ways to describe staggering distances and abstractions beyond our ability to visualise. Yet we still look to give our proudest discoveries human names.
An ancient philosopher saw the dignity of a farmer in the skies, and we have boötes. A fan of 1990s blockbusters made a Tomhanks of a rock hurtling through space. A group of Belgians whose own idea of perfection is a cold beer saw something of their cultural heritage in a tool designed to find new worlds. We call these worlds Trappist-1b—1h. Perhaps under the pretence of a shared purpose, but more likely out of sheer technological limitation, humans have designated space as a common inheritance: a place for cooperation, not division. And in a universe untroubled by human conflict, we can accept a common nomenclature because we have no reason not to. There’s enough space for everyone.
Lead photo: ‘Witch Head’ Brews Baby Stars, NASA/JPL-Caltech.