Q and Alien: What's in an Exoplanet Name?

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As you probably know, Exoplanets can be pretty weird places.

Some of them have atmospheres that are torched black or rain made from molten glass.

But do their names have to be so weird, too? I mean you have names like HD 20504b and Kepler-12c.

Why can't they be named after cool stuff, like Supreme Court Justices or members of the Wu-Tang Clan? First of all, there are thousands of Exoplanets, so coming up with good names for every single one of them would take a really long time.

But more importantly, these names give astronomers really valuable information about each planet.

And when you've got thousands of them to sort through, that's pretty helpful.

A planet name like 'Ghostface' would be cool, but doesn't tell you a whole lot.

One of the most common Exoplanet names is the letters 'HD' and then a whole string of numbers, and then a lowercase letter.

The HD in the number are actually the name of the star that the planet orbits.

Astronomers have massive databases of stars and each one gets a number, so the HD part helps them look up the stars location. The letter at the end tells you in what order the planet was discovered,

so the first one gets a 'b', and then a 'c' and then on down the alphabet.

When a bunch of Exoplanets orbiting the same star are discovered all at once, though usually, the order based on their distance from that star, so the closest one will get a 'b' and then the next one out 'c' and so on.

Now if later on astronomers find a new planet orbiting the same star, it will get the next unused letter, regardless of where it orbits.

Now you might be wondering, why do the planets start with the letter 'b'? That's because astronomers use a capital 'A' to indicate the star in a solar system or the brightest star if there is more than one.

So in a binary system the brighter star will get a capital 'A', the dimmer star will bet a capital 'B' and the first planet would get a lowercase 'b'.

Sometimes, stars with Exoplanets will be named after the mission or the project that discovers them.

So planets found by the Kepler mission will start with the word 'Kepler' and planets that were found by the CoRot mission, will start with the word 'Corot'.

There's been a lot of talk in the scientific community about trying to give Exoplanets more interesting names, and it's likely that in the future some of the coolest discoveries, say that we find an Exoplanet that we know to be a lot like Earth those will finally get names that are easier to remember.

That's it for this Q&Alien.

Keep an eye on PlanetQuest for the next video in the series and all the news and images you can handle.

Because Exoplanet science never stops.

NASA Jet Propulsion Laboratory, California Institute of Technology