Why Are Exoplanet Names So Weird?

Why Are Exoplanet Names So Weird?

If you ever saw an exoplanet named Kepler-452b or HD 189733 b and wondered, what are these names all about? I mean why not call them something cool like ‘Aurora’ or ‘Zephyr’, right?” You’re not alone! Exoplanets are given names that sound like some amalgamation of tech jargon and license plate numbers. But there is some method to this madness.

In this article I’ll help to explain how these exoplanets are named. In the end you will learn why exoplanet names are the way they are, how they help astronomers to keep things organized, and why they’re more meaningful than one might think.

What’s an Exoplanet Anyway?

Wait, but before we get into their names; what is an exoplanet? An exoplanet is a planet that orbits stars outside of our solar system. They are light-years from our home, circling stars we may frequently only glimpse as pinpricks of light.

Finding exoplanets is one of the most exciting fields in contemporary astronomy. It was in 1992 astronomers Aleksander Wolszczan and Dale Frail confirmed the first evidence of planets outside of our solar system around a pulsar (a type of dead star) called PSR B1257+12. Since then we have found thousands of exoplanets using the transit method, where planets block a small fraction of their star’s light and the radial velocity method that measures wobbling of a star by an orbiting planet.

As the number of these worlds has now entered the thousands and new ones continue to be confirmed, naming them can be a bit complicated.

How Are Exoplanets Named?

Rather than getting all poetic about their names (like our solar system planets, named after Roman gods and goddesses), exoplanets don’t enjoy such names. They are named systematically, according to conventions laid out by the International Astronomical Union (IAU), which is responsible for naming objects in space.

Exoplanet names are usually made up of two parts.

1. The name of their host star they orbit.
2. A single lowercase letter indicating the order of discovery

For example:

• Kepler-22b – This is an exoplanet that orbits Kepler-22, and the “b” signifies that it was the first planet discovered in that system.
• HD 209458 b: This planet orbits the star HD 209458 (a star in the Henry Draper Catalog) and the “b” indicates it was the first planet discovered to orbit that star.

The star name itself almost always derives from some sort of catalog, telescope or mission such as the Kepler space telescope or TESS mission. This name cataloging scheme means that no two exoplanets ever have the same name and are called by an exact name associated with its star.

Fun fact:  if more planets are found in the same system they will continue to be labeled consecutively as “c”, “d” and so on down the line. The lower case letters start at “b”, since the star itself is designated “a.”

Decoding the Naming Convention

Now, for some example of exoplanets to help us see how that naming system works in practice:

1. Kepler-452b
   • Kepler: The planet was discovered using data from the Kepler Space Telescope.
   • 452: This is the 452nd star system identified by the telescope.
   • b: The first planet discovered in the system.
2. TRAPPIST-1e
   • TRAPPIST: Short for Transiting Planets and Planetesimals Small Telescope — the name of the telescope which discovered the star system.
   • 1: The first star observed by this telescope.
   • e: The fourth discovered world (note that planets start with “b”)
3. 51 Pegasi b
   • 51 Pegasi: The name of the star itself, referring to the Pegasus constellation.
   • b: the first planet known to orbit this star.
   • Quick trivia: This was the first exoplanet ever discovered around a Sun-like star, and occurred in 1995.

However, we have to admit that this system is highly practical but when you compare it to the nameslikes of “Earth” or “Jupiter”, it really isn’t glamorous. If exoplanets have all of these cool potential names, then why do we continue with this name system?

Why Not Simpler Names?

One would think, such as naming exoplanets after mythological figures, scientists or even pop culture references might help the name be a bit more memorable. But there are perfectly good reasons for the current naming convention:

• Practical: Since we already have thousands of exoplanets and likely billions more to come, this prevents a naming crisis or ambiguity. Like you would even know if “Aurora” was in the Kepler or TRAPPIST system!
• Consistency: Essential for astronomers, the naming system connects exoplanets to their parent stars. Such systematic names are useful in cases where a star has multiple planets, as these names then convey which planet belongs to which star and then the order of discovery.
• Objectivity: Names in science usually try not to be biased. This attention to catalog numbers and sequences keeps the focus on science, not cultural preference or personal choice.

Are Weird Names Always Bad?

Now, the systematic process may seem cold and heartless at first, however there are some benefits. For one, it opens the door for creativity in other venues. The IAU also sometimes holds naming contests open to the public, in which people can suggest names for exoplanets and respective stars. For example:

• Dimidium was named by the public for 51 Pegasi b, meaning half mass to Jupiter.
• Helvetios: 51 Pegasi’s parent star was named for a Celtic tribe in Switzerland.

It is through these contests that the general population builds a tie to astronomy, but the systematic names stay in place for scientific discussion. That means exoplanets have names like “Kepler-22b” — not exactly poetic, but easy enough for research and allowing room for nicknames.

Closing Thoughts

Exoplanet names may sound bizarre, but there is a certain elegance in their specificity. These are sort of like cosmic GPS giving an astronomer direction from one side of the Universe to another. They may not be poetic like “Venus” or “Mars,” but names like that of Kepler-452b are the result of hard work in finding and cataloging planets beyond our own solar system.

So the next time you hear about an exoplanet with a weird name, just remember that behind every name there is a story of discovery, collaboration and the never-ending quest to answer questions that have plagued mankind ever since we stared at the stars. And who knows? Perhaps one day we will be visiting them ourselves and providing these new worlds with our own names!

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