How are Astronomical Objects Named?
Ever looked at the night sky and wondered how we arrived at naming the big, round, cheese-like
object above us the “Moon”?
Or how a simple bunch of seven stars arranged at some way made us think “Hey, that looks
like a bear.
Let’s call that Ursa Major!”
Or how we lost words at something so magnificent, and so beyond our understanding that we just
end up calling it “The Great Attractor”?
Come with us in a journey of discovering how these space objects are named!
Who names the objects in space?
The task of naming and cataloguing what we see in the evening sky belongs to a special
group under the International Astronomical Union, or the IAU.
Ever since their founding in 1919, it has been their duty to set up guidelines, and
form committees that determine the appropriate naming schemes for planets, stars, constellations,
satellites…practically everything that is observable in our known universe.
Thanks to these guys, we have a know what to call any star we point in the night sky.
The Solar System Family: Planets Let’s start our adventure by knowing more
about our closest neighbors, shall we?
If you’re a fan of classical mythology, it’s hard to miss how almost all the planets
in our Solar System are named after popular mythological characters.
Back in the ancient times, five of the nine planets were observable using the naked eye.
Well, what else do Romans look up to?
Their deities!
This is the reason why the astronomers thought of naming these planets according to the traits
of their gods.
For instance, the prettiest and brightest one is compared to the goddess of beauty,
Venus.
One planet was bright red like blood, so they thought it is reminiscent of the god of war,
Mars.
Another moves so fast that it reminded them of the messenger god, Mercury.
The slowest and farthest one must be an old god and the father of them all, Saturn.
and, the biggest one is the king, Jupiter.
This theme caught on, so, when three more planets were discovered -- Uranus, Neptune,
and Pluto – this became the standard theme.
Of course, this is all before Pluto was demoted to a dwarf planet, which is a story covered
in another video, by the way.
The same system was applied to naming minor planets and asteroids, with preference to
female characters from the Greco-Roman classics, like for instance, Vesta, Pallas, Juno, and
Eros.
Everyone in the family gets the same theme.
The Solar System Family: The Moons Now, we move on to the orbiters of the planets:
natural satellites, or moons.
Technically, there are a few ways to name moons.
There is a boring way, and then there was the fun way.
The boring way was naming the moon with the planet it revolves around, plus a Roman numeral
equivalent to its order of closeness to the planet.
For example, if I had found a moon on Saturn, and it’s the 7th closest to it, its technical
name would be “Saturn VII” Since the planets were already named before
the Greco-Roman gods, astronomers then decided to extend this theme to the moons.
Particularly speaking, astronomers choose the names of mythological characters that
are related to the planet which they revolve around.
For instance, the Martian moons are named after the sons of Mars, Phobos and Deimos.
The moons of Jupiter were named after either his lovers or children, like for example,
the Gallilean moons, Io, Ganymede, Callisto, and Europa.
Saturn’s moons were named after Titans and Giants, since Saturn himself was a Titan.
Neptune’s moons were characters that were somehow involved with the sea, and Pluto’s
were characters who once walked the underworld, and Uranus’ were taken from the Shakespearean
and Alexander Pope’s universe.
Even a lot of planetary features, like craters and mountains, have names derived from mythology.
I think we can say that if we were to study all the names of the objects of the solar
system, we would also learn a lot about Greek and Roman mythology, right?
Talk about a real renaissance man.
The Solar System Family: Comets You know how big families always have that
one cousin who rarely shows up and is often on the move?
Well, if the Solar System is a family, then that cousin is the comets.
In the early 20th century, these objects were named after the person who discovers them.
A few examples of these are Halley’s Comet, discovered by Edmond Halley, and Encke’s
Comet, discovered by Johann Franz Encke.
This also became the naming convention for the preceding discovered comets, allowing
up to three people names separated by a dash, like IRAS–Araki–Alcock…that is until
people who has dash on their names made it problematic.
This was when our original heroes, the IAU, stepped in to standardize the naming system.
In 1994, they started naming comets according to the year it was discovered, followed by
an alphabet equivalent of the order at which half of the month it was discovered in the
year.
For example, if I had discovered a comet in 2003, and it was the 17th discovery that year,
that comet’s name will be “Comet 2003q”, which later changes to “Year + order of
perihelion passage in Roman numeral” (if our previous example is the second to pass
perihelion, then it becomes 2003 II), once its orbit is established.
However, as technology caught up, more comets were discovered, and astronomers ran out of
alphabet and subscripts to add to each letter and the system became a mess.
What do we do when systems become too messy?
We set up new ones.
Ever since 2003, the comets are now named using the following combination:
A prefix indicating the nature of the comet’s motion, for instance, P, for periodical, and
C, for a non-periodic comet, followed by a slash, followed by an alphabetical equivalent
for either first or second half of the month designated sequentially, then, the order at
which it was discovered that half month.
To put it in perspective, say I have discovered a non-periodic comet in the first half February
of 2020, and this is the 2nd comet found at this time.
Using our system, that comet will be named “C/2020 C2”.
C for non-periodic, 2020 for the year, C, since the first half of February is the third
half-month for the year, and 2 since it is the second to be discovered.
Quite a mouthful, isn’t it?
Constellations: The Ancient Astronomers’ “Where’s Waldo?”
If there’s anything that our old astronomy folks had the most fun of, I’m willing to
bet it’s naming the constellations.
It would be crazy to not admit how they went full creative mode with that one, I mean,
how do you even see a bear just from seven stars, right?
Ancient astronomers had to find a way to somehow remember the huge number of stars that they
see in the night sky.
And, the best way they thought, is to find patterns among the order of stars.
They found all sorts of stuff: shapes of animals, like bears, eagles, birds, fishes; of mythological
creatures like unicorns, Pegasus, centaurs; of familiar items, like a ship’s keel, easel,
a carpenter’s level; and, surprise, surprise, of mythological characters, like Hercules,
Cassiopeia, and Andromeda.
Their efforts of labelling star groups in the effectively produced a concise map of
the night sky, which eventually lead to the formation of the celestial sphere, or the
theoretical observation sphere, at which the observer is at the center of.
To infinity and beyond: Stars Now that we’re moving away from the solar
system and towards what’s beyond, it gets a bit more complicated than just simple mythological
characters.
Remember how in the previous section, we discussed how the names of the constellations became
the reference in naming the stars and other objects?
Well, that’s how everything seen in the celestial map is now named.
Let’s start with the stars.
The earliest astronomers to name stars visible to the naked eye was Hipparchus, successfully
tagging around 850 stars.
Think that’s a lot of stars?
Well, not according to Johann Bayer, beating that record with about twice what the previous
guy did!
All with the naked eye.
Man, they are either extremely bored or extremely passionate about naming stars.
Of course, star observation and naming weren’t a feat exclusive to these two pioneers.
There were stars that already had well-known Arabic, and some Latin, names.
This system would work fine, but since transliteration is such a bothersome friend of passing down
historical knowledge, the names could sometimes rouse debates on how they are properly labelled.
For example, there isn’t a standard way to call the star Almach, since it has an Arabic
origin.
It could be spelled Almaach, or Almak, or Alamak, or Alberta.
I was just kidding about the last one, but you get the point.
There are also instances where stars have more than one name, like Gemma or Alpheca.
Of course, there was also the problem of how unprecise the old catalogs got, resulting
in some stars having the same name in a different constellation.
It’s like having a Mark in work and another Mark from soccer class.
This is why in 2016, the IAU launched WGSN, or Working Group on Star Names, with the specific
goal of finding a systematic way to catalogue and standardize how every star that can be
found in the celestial sphere would be named.
In this new system that they developed, stars are catalogued either according to the constellation
group they belong to, as unique individual items, or a variation of both.
The top brightest stars, like Sirius, Arcturus, Vega, retained their old names, since everyone
is already familiar with them, along with a handful of also popular ones.
The two most preferred designation techniques were the Bayer and Flamesteed designations.
In the Bayer designation, stars are named by a Greek alphabet indicating the order they
are catalogued, following the constellation name.
Let’s say we have a hypothetical constellation, Barney.
Barney has 5 stars.
Using the Bayer designation, Barney’s stars will be named α Barney, ß Barney, Γ Barney,
δ Barney, and ε Barney.
That’s a lot of Barneys.
Now, this system is fine.
That is until you include the gigantic constellation, Centaurus.
How does it become a problem, you ask?
Well, the Greek alphabet only has 24 letters.
Centaurus has 281 stars!
Huge mismatch.
For conditions like these, it is preferable to utilize the Flamesteed designation.
In this method, numbers are used instead of letters, so we can go up to a million and
we’ll still have a unique indicator for each star.
On the other side of the coin, we have the designation methods that aim to catalogue
stars by a threshold magnitude, like the previously mentioned Bright Star Catalogue, the Henry
Draper Catalogue, and the Guide Star Catalogue II, to name a few.
Finally, there is the variable star designation which is some kind of special variety of the
Bayer designation.
This method is used for stars which brightness varies from time to time, as observed from
earth.
The Exoplanets We all know that our sun is a star, and that
it has its own set of orbiting objects.
The next question is, do other stars have their own planets, asteroid systems, comets,
and the like?
If you’re familiar with the gravitational laws, particularly how it is described in
general relativity, the sheer massiveness of stars is conducive to the availability
of objects revolving around it, like planets.
Since these planets are beyond our Solar System, they are more popularly labelled as exoplanets.
So, okay, cool!
There are exoplanets.
But the question we’re interested in answering is: how do astronomers label them?
In essence, there aren’t really any set of rules that are standardized for naming
exoplanets.
The current system the IAU rolled out is an extension of the constellation-based star
naming system.
To put it simply, to name an exoplanet, we simply use the star it revolves around as
reference.
Let’s take for example the star, Alpha Centauri.
If a planet was found that is directly affected by the star’s gravity, and it is the first
found within that star system, then, that planet’s designation becomes “Alpha Centauri
a”.
The preceding planets, then, becomes “Alpha Centauri b”, “Alpha Centauri c”, and
so on and so forth.
Galaxies and Everything Else Of course, the universe isn’t purely composed
of just planets, stars and moons.
Astronomers also happen to find other objects that don’t belong to these categories and
must be named uniquely.
For instance, there are magnetic rotating neutron stars emitting radio waves called
Pulsars.
They are named using a prefix of “PSR”, which stands for ‘Pulsating Source of Radio’,
followed by a numerical string indicating its right ascension and degrees of declination.
The birth, or Novae, and death of stars, or Supernovae, can also be designated using conventional
names!
For Novae’s, the naming scheme is “Nova”, the constellation where the Novae is found,
plus the year it was discovered.
For instance, a Nova observed in Capricorn in 2010 will have the name “Nova Capricorn
2010”.
On the other hand, for the Supernovae, we use a prefix of “SN”, followed by the
year of discovery, plus an uppercase alphabetical designation on the order it was discovered
that year.
The third supernova observed in 2010 should have the name “SN2010C”.
Now, these last two items we will tackle is the black sheeps of the group: they absolutely
have no standardized naming convention!
If we ride a space ship and keep moving, eventually we will see that all the stars are clustered
together in groups which we call galaxies.
Similar to black holes, they also don’t have naming rules.
However, there some astronomers successfully named a few, according to some arbitrary characteristics.
For instance, we have the Andromeda galaxy, derived from its position in the constellation
of Andromeda.
The sombrero shaped, Sombrero Galaxy, and it’s loopy cousin, the Whirlpool galaxy.
And of course, our very own, Milky Way galaxy, because when it was first observed, it looked
like a road of milk.
No kidding.
Black holes, the superstar of every galaxy, have no standard naming schemes.
Some are named according to which catalogue they are first mapped, like NGC 4151, some
according to the constellation, for instance, Cygnus X-1, and some according to the instrument
used upon discovery, like black hole RX J1131−1231 derived from Chandra X-ray Observatory.
From completely systematized, to completely chaotic and all-over-the-place, we can certainly
say that learning about how astronomical objects were named was an awesome adventure!
Would you have come up with better naming conventions, if you were given the task by
the IAU?
Let us know in the comments down below!
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