What type of creature is Cetus constellation?

By Tom Burns - Stargazing

For all of human history, we have viewed the sea with mixed feelings of wonder and dread. The oceans are vast and beautiful, but beware, mateys, there be monsters in the Great Deep.

The largest of all creatures, the whale, is a denizen of the dark ocean.

The ancient Greeks, especially those who lived on the coast, looked south this time of year and saw Leviathan rising out of the sea. They called it Cetus, the Sea Monster.

Leviathan still skulks among us. Look southeast just after dark, and you’ll see what I mean. Cetus is the fourth-largest constellation, but its stars are not exceptionally bright.

You’ll see a circlet of faint stars representing the head of the beast. Its long neck stretches down and to the right. Its fat body and incongruous tail extend downward and closer to the horizon.

Cetus abides in a region of the sky the ancients called “The Sea.” We moderns refer to the area as the “Watery Constellations.”

To the east of Cetus is Eridanus, the “River.” In 1848, Stellar cartographer Elijah H. Burritt depicted it as resting its two front paws immersed in Eridanus.

To the north is Pisces, the Fishes. To the west are Aquarius, the Water Bearer, and Capricornus, the Sea-Goat. To the south is Piscis Austrinus, the Southern Fish.

Around 150 CE, the Greek astronomer Ptolemy recorded the 48 classical constellations in his Almagest. Among them was Cetus.

Although the attribution is uncertain, some astronomical historians trace the constellation back to the ancient Mesopotamian culture of Babylonia. The Babylonians may have identified the constellation with their goddess Tiamat, variously depicted as a dragon, a sea serpent, or a mermaid-like creature.

She is the primordial sea goddess, representing both the chaos that prevailed before the creation of the cosmos and the creative force that helped mold order out of that chaos. She is thus both a monster and a creator.

Today, many astronomy aficionados identify the constellation as a whale. However, if Cetus is a whale, it is a bizarre one. The ancients depicted it with large, gaping jaws and the forelegs of a land animal. It had a huge, scaly body, terminating in a long, coiled tail like a sea serpent.

Sixteenth and seventeenth stellar cartographers all depicted the constellation with the tail of a fish. The front end varied with the artist.

The representations ran the gamut from a dragon’s head, a dog, a horse, and an elephant, complete with one tusk and a trunk. Only twice (that I know of) is Cetus depicted as a whale, first by the Dutch cartographer Willem Blaeu and later by the German Cellarius.

In any case, this is not the friendly singing whale of today’s environmental movement. It is a hideous, flesh-eating monster, ravenous with the lust for human blood. Constellation researcher Robert Brown describes Cetus as representing “the chaos of the deep.”

Cetus is also an amphibian. It dwells deep within the sea, but it brings death and destruction when it rises above the ocean’s surface. As Julius Staal rather colorfully put it in 1911, “Cetus is the personification of everything bad, … an evil, lumbering creature, smelly and dripping with seaweed.”

The natives of northern Brazil saw Cetus as a Jaguar but also kept the oceanic connection. According to Julius Staal, they saw the Jaguar as the “personification of the God of Violent Storms and Hurricanes.”

An old Greek myth about Andromeda and Perseus exemplifies Cetus’s evil intent. When the princess Andromeda was chained to a rock as a sacrifice to the gods, Cetus rose from the waves to eat her. Luckily for her, The Greek hero Perseus was nearby.

According to one version of the story, he held up the bloody head of the gorgon Medusa, and the sight of her hideous face turned the sea monster to stone,

In another version, Perseus slew the beast, but the carcass survived. The Roman writer Pliny claimed that its skeleton, measuring 40 feet long and six feet wide, was eventually brought to Rome. Saint Jerome claims to have later seen Cetus’s bones during a visit to the city of Tyre.

Cetus also has a biblical connection. Seventeenth-century commentators wrote that Cetus represents the whale that swallowed Jonah.

Others connected Cetus with a passage in the Book of Job (Job 41), which uses the strength and size of Leviathan as a metaphor for the power of God.

Near the center of the constellation is a stellar mystery that puzzled astronomers for hundreds of years. Amateur astronomer David Fabricius first recorded the star Mira in 1596.

Its name is usually translated as “The Wonderful One.” But my daughter Krishni, a Latin scholar, tells me that the best translation into English would be “The One that is Marvelous (or Miraculous) to Look At.” English is sometimes a very dull language.

In 1638, Phocylides Holward, a Dutch astronomer, noticed that Mira varied in its brightness over many days.

That discovery was startling. From our earliest times, humans had believed that the stars were fixed in their brightness, a condition that reflected the unchanging beauty of the universe.

A star that varied in its brilliance was more than just a curiosity. It questioned the perfection of the cosmos.

After long and careful study, French astronomer Ishmael Bouillaud determined the period of the star’s pulsations. Over 333 days, Mira slowly pulses from bright to dark and back to bright again.

In 1662 Polish astronomer Johannes Hevelius named the star Mira in his Historiola Mirae Stellae (Wonderful Story of Stars).

At its brightest, it is easily visible to the unaided eye. At its dimmest, you can’t see it at all.

On a personal note, there’s nothing quite like scanning for one of your favorite constellations and realizing abruptly that one of its stars is missing.

An astronomer might put its fluctuations in brightness as follows. At the brightest part of the cycle, it reaches somewhere between second and fifth magnitude. At its dimmest, it can cycle down to ninth magnitude.

To understand what that means, dear reader, we will have to take a slight diversion down the magnitude trail.

The magnitude scale was invented around 100 BCE by the Greek mathematician and astronomer Hipparchus of Nicaea. He wanted to produce a way of comparing stellar brightnesses to each other.

Unfortunately, the numbers go backward, at least from a modern point of view. A first-magnitude star is brighter than a second magnitude star, for example.

Vega, which shines at zeroth magnitude, is very bright. However, the scale has to reach into negative numbers to account for all the objects in the sky. The sun blazes at -27, and Venus shines very brightly at -6.

A fundamental benchmark is naked-eye visibility. From the darkest, most transparent sky, average observers will just barely see a sixth magnitude star with their eyes alone.

Thus, when Mira is brightest, it is about as bright as second-magnitude Polaris, the North Star. When its high-end brightness is only fifth magnitude, Mira is only just above naked-eye visibility.

At the dim end of the 333-day cycle, Mira dips down to ninth magnitude and requires a relatively sizeable amateur telescope to see.

One further complexity: In its modern version, the magnitude scale is logarithmic. Each step of one magnitude changes the brightness by a factor of about 2.5 times.

The upshot of all of this is that Mira varies wildly in brightness. At its minimum magnitude, the star is 1,000 times fainter than its highest brilliance and 1/20 as bright as the dimmest star visible to the unaided eye.

Hevelius got it right when he named the star. “Mira” is the Latin root of the English word “miracle.” To a time unused to such intense variations in stellar brightness, Mira must have seemed miraculous.

For a long time, Mira was the only variable star known, but now we know of thousands. The General Catalogue of Variable Stars includes more than 46,000 of them in our Milky Way galaxy alone.

It wasn’t until the twentieth century that astronomers solved the mystery of Mira’s pulsations. Mira is a dying red-giant star.

As stars begin to run out of the hydrogen that fuels their hydrogen-bomb reaction, they go through periods of intense explosion followed by periods of relative inactivity. They expand and contract, like the beating heart of a great beast, swelling to many times their original size before they shrink again and repeat the process.

Go out and look at Leviathan, oh ye stargazers. Tremble with dread at its power. But most of all, gaze with wonder at the beating heart of a dying giant.


By Tom Burns


Tom Burns is the former director of the Perkins Observatory in Delaware.

Tom Burns is the former director of the Perkins Observatory in Delaware.