Cetus: A Greek Astronomical Sea Monster

The shere depth and width of the oceans that are found on our planet make them fascinating, mysterious, or even scary places to think about. In case you were wondering, the human species hasn’t even explored about 80 percent of the oceans on our planet. Some might wonder why we make expeditions to Mars while we don’t even know what exactly is going on on our own planet.

Creatures that live in the deepest parts of the sea remain mostly unknown. Even now we don’t have the slightest idea. So, it’s not hard to see that people would use their own imagination to fill in the gaps about what these creatures are. Just think about Nessy, the monster of Loch Ness.

Although they could explore a fair bit, the Greeks didn’t know a whole lot about the oceans either. Without being able to investigate beneath the surface of the ocean, they figured that the underwater world was actually quite similar to that on land. The sea monsters that they would imagine therefore were pretty intriguing oftentimes with interesting features.

Cetea: the Sea Monster of the Greeks

In Greek mythology, the general name which was used to refer to sea monsters was Cetea. Usually, they were depicted as gigantic, serpentine-like creatures with rows of sharp teeth. But, they would also be shown with features that we normally see with land creatures, like rabbit ears or antlers.

Why were they important in mythology? Well, mostly because they served the sea gods. There are plenty of sea gods, but the monsters would particularly be of great use for Poseidon

It goes without saying that the sea monsters were ferocious animals. After all, they are called monsters. As employees of Poseidon and the other gods, they would show up if the gods that they served were unhappy about the way things were going in the mortal world.

Normally it is believed that they were pretty tolerant towards the gods and nymphs of the sea, but once in a while they got their occasional tantrum. Even towards their owners.

Personifying Natural Phenomena

Recent research actually suggests that the myths surrounding the attacks of Cetea find their roots in tsunamis or earthquakes in a particular region. 

They believe that natural disasters with severe consequences would be a topic of conversation for a long time. But, after a while these stories get adjusted, accumulating to a whole different story. This way, it is possible that the Greeks believed that tsunamis or earthquakes were actually caused by the Cetea. 

Cetus: More than One Monster?

One of the most prominent stories about a Cetea is the one on Cetus. But, it’s a bit contested what Cetus actually consisted of. There is one particular story that is often referred to when Cetus is described, which we will discuss later. However, the term cetus can also be seen as the singular form of Cetea; so a single sea monster. Many cetus therefore become Cetea.

Indeed, cetus was used to refer to nearly any large sea creature. Well, maybe not any. Mostly the ones that had the same characteristics as whales of sharks

For example, they were believed to have a broad, flat tail, lifting its head above the surface to inspect any ship that was passing. Also, mourning sounds were often characterizing a cetus. Both the tail and the sounds are, of course, also characteristic for whales.

What is the Myth of Cetus?

So cetus can refer to any whale- or shark-like sea monster. However, the most intriguing myth is the one when Poseidon sent one specific cetus to wreak havoc on the kingdom of Aethiopia: modern day Ethiopia.  

Terrorizing Aethiopia

The victims of the myth of Cetus were located in Ethiopia. Poseidon was mad at one of its rulers, since he thought that their queen was too reckless with her words.

So what did she say to make the sea god Poseidon so full of anger? 

Well, she stated that she and her daughter, princess Andromeda, were more beautiful than any of the Nereids. 

The Nereids are a specific form of nymph, often accompanying Poseidon when he was guarding over the oceans. They also appear in the story of Jason and the Argonauts, so this group of nymphs is certainly important in Greek mythology. 

Queen Cassiopeia probably wasn’t fully aware of their importance, or at least not the reaction it would generate in Poseidon. Indeed, he sended Cetus to bring across a message: she had to be more careful with her words.


A devastating attack would follow for the kingdom of Cassipeia’s man, King Cepheus. In order to respond in a way that didn’t anger Poseidon even more, Cepheus consulted a wise oracle. An oracle, in this sense, is basically a medium through whom advice or prophecy was sought from the gods. 

READ MORE: Oracle of Delphi

Sacrificing Andromeda 

The outcome of the oracle wasn’t all that happy, unfortunately. The prophecy was that King Cepheus and Queen Cassiopeia had to sacrifice their daughter Andromeda to Cetus. Only then, the attack would stop.

Yet, they made up their mind pretty easily. The princess was quickly chained to an ocean cliff. Dinner served, war solved.

Death of Cetus

Or actually, maybe not.

As soon as Cetus tried to devour Andromeda, Perseus flew by. He is another important figure in Greek mythology, known as the son of Zeus and famous for his winged sandals. Zeus’ son just returned from a victory over Medusa: a serpent-haired monster. As some of you probably know, anyone who would look in the eyes of Medusa would turn into stone.

Perseus saw the princess and immediately fell in love with her. Conveniently, he was carrying the head of Medusa when he flew by. One and one is two, so Perseus flew down to save Andromeda, just when Cetus was rising from the water to attack. 

In the most common variation, Perseus exposed the head to Cetus, turning him into stone. But, in another variation, he didn’t bring the head. Instead, Zeus’ son stabbed Cetus with his sword until he died. Although there is a bit of variation in this regard, the end result stays the same. 

Constellation Cetus

Cetus is not only known as a monster, since it might actually be even more famous for it being a constellation of stars. It was first mentioned by the Greek astronomer Ptolemy. He was of great influence in many different fields, including astronomy.

The names he would come up with were based on the mythological figures of Ancient Greece. This specific constellation was given the name Cetus since it looked like a whale, at least according to Ptolemy. 

What Time of Year is Cetus visible?

The constellation Cetus can be seen in the northern hemisphere somewhere in the late fall and early winter. It is visible at the latitudes between 70 degrees and -90 degrees.

A large distance indeed, which is mainly due to the fact that it is a very large constellation. The fourth largest of all, in fact. Since whales are also known as the largest animals on earth, this should come as no surprise. 

The constellation Cetus lies in the middle of a part of the sky that is recognized as ‘The Sea’ by mythologists. It contains besides Cetus some other water related constellations, namely Eridanus, Pisces, Piscis Austrinus, and Aquarius. 

The Brightest Star and Other Stars of Cetus

So, there are several well known stars in the constellation Cetus. We won’t go over all of them, but some are important to realize the size and significance of the constellation that is closely connected to our monster. 

Beta Ceti is the brightest star in the constellation. It is an orange giant that is located about 96 light-years away. From earth it is perceived as the brightest star exactly because it is relatively close to earth. Beta Ceti is, and was, also recognized by Arabic astronomers as ‘the second frog’. Maybe a bit less frightening than how the Greeks saw it. 

Another notable star is Menkar (Alpha Ceti), a red giant star located 220 light-years from Earth. Alpha is, in theory, more shiny than the Beta Ceti. But, because it is located around 124 light-years further away (that is, 124 times 5.88 trillion miles), we don’t perceive it as bright as it actually is.

Another important star goes by the name of Omicron Ceti, or wonderful star. It got this nickname because the star has quite unusual fluctuations. We won’t dive deeper into it, since this is a mythology article after all. But, if you’re interested, be sure to check out this website

Why the Constellation Matters?

You might wonder: I thought we were talking about a monster, why all the talk about the stars? Very good question. 

The answer lies in the fact that it contributes to discovering the connection between myths, everyday life, knowledge, and natural phenomena. 

What is Valid Knowledge?

It might be a bit odd to hear, but the reliance on scientific knowledge as we know it today is a very recent development. Science is nowadays seen as the absolute truth. Indeed, it should be to a very reasonable extent. However, it took some time to come to the point where we are now. 

The ancient Greeks, like many other ancient and contemporary civilizations, had a totally different way of expressing and researching things. Aristotle, for example, would never be taken seriously if he would use his ‘research’ principles in our day and age. That’s because most of it was based on observing. Yet, his knowledge is the very foundation of scientific research today.

To add, both Aristotle and the one who named the constellation, Ptolemy, were researching nearly everything. Math, biology, chemistry, biology, you name it. It is quite uncommon that someone is ‘specialized’ enough in every field to be an expert on all these topics today. This signifies that the Greeks had a different way of going about things. 

Of Stars and Myths

So, while this website is full of interesting articles on a wide variety of myths, we actually have very little knowledge about the knowledge of the ancient Greeks. Let alone how they came to this knowledge.

What we do know for sure, is that the constellation Cetus got its name from the monster that we discussed throughout this article. It shows that the ancient Greeks saw tight connections between the stars and mythology. Maybe even because they were able to imagine a monster like Cetus, the Greek astronomer Ptolemy was able to see the constellation in the sky. 

The relation between the sea monster Cetus and the constellation Cetus help us to grasp how the ancient Greeks thought. Well, at least for a little bit. 

A Sea Monster Like No Other

If you compare the story of Cetus with that of other Greek mythological stories, it might be a bit different.

The main reason for this is that the idea of Cetus is necessarily something that finds its roots in pure imagination. Sure, this is also the case with other mythological stories. But remember, the ancient Greeks had very little knowledge about anything that was happening in the water of the oceans. 

While stories like the ones about the Titans are closely related to human characteristics and traits, the Greeks just didn’t really know what to do with the creatures underwater. Therefore, they don’t represent a certain morality, value, or directly says something about human characteristics. 

The story of Cetus can be seen as a lovely story in and of itself. But, it should also be recognized for its value in the wider discussion and research surrounding the knowledge of the ancient Greeks. Maybe there is some value in the ancient ways of reasoning after all.  

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