Astronomical Naming Conventions

So planets are named after Roman Gods, except Uranus is named after a Greek God. And Earth is named after…well…the Earth?

And the designations of objects to a planet uses the initials of the planet, except Mercury which uses a H for Hermes…the Greek God.

And there is nothing orderly with the naming of black Holes!

Naming conventions exist in astrophysics to catalogue and search for items in a simple manner. Often times, the name will also act as a brief description of the item, which is extremely useful if you understand how to read the description!

We have a system to explain many objects in space, such as supernovae, however there are also many exceptions to this. This is mainly because our vocabulary for these have built over history and tend to have more of a guideline than a rule.

The Solar System

The main objects in the Solar System have had names since the Ancients, such as the Sun, the Moon, and Planets up to Saturn. Since these planets have Roman names (except Earth), we named both Neptune and Pluto accordingly. Uranus is the exception, and its naming is quite an odd story in itself! Originally the discoverer -Herschel – planned to name it Georgeum Sidus, but thankfully that was Changed to Ouranos, then Uranus thanks to Bode.

Most minor planets are given Roman names, for example Ceres and Vesta. However, there are a few exceptions here and there such as Pallas named after the Greek Goddess Pallas Athena.

Any asteroid or comet or moon type satellites will usually have a lengthy numerical name before it’s given anything fancy. This starts off with a letter and a slash, for example S/ for satellite, R/ for rings, and D/ C/ and P/ for different comets. That’s followed by the year the object was discovered, then it might be followed by a planetary designation which is usually just the initial of the planet (Mercury’s is H). If we discover another thing in that year, we’ll put a number after the planetary designation.

Here they are, the great and awesome Ymir! Credit: ESO.

For example, Neptune’s newest moon Hippocamp was designated S/2004 N 1, discovered in 2004 and the only Neptunian satellite discovered that year.

One of Saturn’s awesome new Norse moons, Ymir, was a satellite discovered in 2000. It was the first one they discovered that year, so it’s initial designation was S/2000 S 1. Skathi was the 8th moon discovered that year around Saturn, so it was called S/2000 S 8. They haven’t named all the moons yet, and I’m hoping they’ll name 2 after Laufey and Rán since they already have Farbauti and Ægir!


Of the millions of stars we’ve seen through telescopes, less than 1’000 have proper names. Most of these are Arabic, such as Betelgeuse, but there are some like Capella which aren’t. A very small amount of stars are named after People such as Barnard’s Star.

Vega by Francisco José Sevilla Lobato

Many stars will be catalogued using Bayer or Flamsteed designations, which use either a Greek/numerical symbol and an abbreviation of the constellation they belong to, or they’ll just be named according to their coordinates. These are only 2 of the many catalogues, but frankly we just have far too many stars to catalogue! We discover so many each year that one main designation systems would be extremely complex.

Variable stars don’t quite follow the Bayer trend. Instead of Greek letters or Numbers, they will have their constellation preceded by the letter R. If R is taken, then astronomers will use the next letter up to Z. Once Z is done, they’ll use RR, then RS up to SS and finally ZZ. The first letter has to be closer to A than the second (so no SR or ZY for example). Once those are taken up, they’ll start with AA, and go up to QZ (but we miss out on the Js). Once these 334 combinations are done, then we’ll start with V335 and go upwards.

I had a headache trying to understand this.

Pulsars begin their designation with the abbreviation PSR, meaning pulsating source of radio. This is followed by an abbreviation for the epoch, then the pulsar’s right ascension and declination. Older stars use the Besselian Epoch, and newer stars use the Julian epoch. So nice and easy, right?


Supernovae are given the prefix SN, followed by the year of discovery, then an uppercase letter from A to Z. If all those letters are used up in the year, then they’ll be named from aa to zz. For example SN 2005gl was the 194th supernova discovered in 2005.

This is extremely simple and pretty, but this is where simplicity in the naming stops.

Black Holes

Artist’s Impression of Black Hole

Black holes are too great to be named, I mean it! There is no naming convention for these bad boys!

We just give Black holes the typical NCG/Messier style names, or random stuff like TON 618 or Cygnus X-1.

The X-1 naming is sometimes assigned to objects which are an X-ray source, such as X-ray binaries. These systems will sometimes have a black hole.

Quasars or Quasi-Stellar Objects, similarly to black holes, will have no real naming convention. They’ll be assigned a catalogue designation, or they’ll seldom use the QSO or QSR prefixes.

Alternatively, some objects will take the name for the observatory they were discovered in. TON 618 was named after the Tonantzintla Observatory. Either that, or I’ve put 2 and 2 together to get 9!

We’ve just spiralled off into a rabbit hole, but that’s all I have for this week. This post took ages to research, I guess because our naming conventions seem to be just all over the place! I’ve missed out on so many areas of space, so feel free to do a little studying and share anything you find!

One comment

  1. I applaud you for doing this research and trying to straighten all these naming conventions out for us. It’s a mess, I know. When I’m writing Sci-Fi, I try to think about what naming conventions might be used in the future. An element of conflicting or confusing naming rules adds a bit of realism to whatever names I come up with, I think.

    Liked by 1 person

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