Famous constellations like the Big Dipper and Cassiopeia are the first we recognize in the sky. But do you know how many there are in all? How do you identify them, and which ones are part of the zodiac?
The stars may be located at extremely variable distances from our planet, but seen from Earth, the night sky constitutes a veritable celestial vault onto which the stars appear to be projected. Used in particular by navigators, shepherds, and travelers, the stars are precious indications of time and orientation. Since ancient times, different cultures have distinguished silhouettes in the sky and assembled groups of stars into identifiable shapes, illustrating their founding stories and divinities.
The great mythological figures of the civilizations that observed and named them can be found here. Some of them were depicted on tablets, enabling us today to date these practices and understand the relationship the ancients had with the stars.
Western constellations are mostly inherited from Greek mythology. Ancient astronomers named over forty constellations visible from the northern hemisphere. The International Astronomical Union later formalized all of these figures, adding the constellations visible in the southern hemisphere, so that every point in the sky is associated with a constellation and the entire celestial vault is now mappable.
You may know some of them by name, such as the Big Dipper or Cassiopeia, without necessarily being able to find them in the sky. Some also evoke the signs of the zodiac or are the subject of debate, halfway between astronomy and astrology. What does science think, and what are the northern and southern constellations? Let’s take a stroll through the stars!
What Is a Constellation?
A constellation is a group of stars with an associated geometric figure or design. Since the dawn of time, stargazers have imagined and named the figures represented by the stars in the sky. A number of constellations derive from Greek mythology, but other cultures have also identified shapes in the starry sky. The International Astronomical Union has officially mapped the heavens, identifying 88 constellations delimited by borders.
What Are the Most Well-Known Constellations?
There are 88 constellations, ratified by the International Astronomical Union in 1930. In order to get their bearings and identify the stars, successive observers of the celestial vault created these figures, which cut out the starry sky. Some of these constellations are better known than others and are relatively easy to spot in the sky:
Ursa Major (Great Bear)
Depicted on the Alaskan flag, the Big Dipper is certainly the most famous constellation of all. It represents Callisto, a divinity with whom Zeus had an affair. Hera discovered her husband’s betrayal, turning Callisto into a bear. Arcas, the mistress’s son, suffered the same fate and became the Little Bear.
To observe it, all you need to do is spot the well-known saucepan-shaped group of stars. This is part of the Big Dipper constellation and revolves continuously around the Pole Star, which remains fixed night after night.
Ursa Minor
In Greek mythology, the Little Bear is the son of Callisto. Callisto and her son are said to have been transformed into bears after Zeus’ wife discovered his affair with her.
This constellation is easy to spot because it’s always in the same area of the sky. At the end of its tail is the Pole Star, which is particularly bright and fixed in the sky.
Cassiopeia
Constellations like Cassiopeia, the Big Dipper, and the Little Dipper may be seen at any time of year. Cassiopeia rules Ethiopia in Greek mythology.
Its distinctive W or M form, depending on its directional location, makes it easy to see in the sky. In dense clusters of stars, it might be difficult to see, but with practice, you’ll be able to spot it in no time.
Orion
Orion, the hunter represented by the constellation, is a macho figure with a legendary lack of fear. After being accidentally killed by Artemis (the Greek goddess of the hunt and nature), he was able to reunite with his dog, Sirius (the dog star).
Look for a rectangle formed by three brilliant stars that cuts across the sky to find Orion. This is the hunter’s harness. In the northern hemisphere, this constellation may be seen all through the winter.
Canis Major
Sirius, the brightest star in the sky, is part of the constellation Canis Major, sometimes known as the Great Dog. An alternate history for this dog can be found in Greek mythology. The constellation of Orion, somewhat farther away, is another possibility, as are those of Actaeon, Aurora, and Ulysses.
The brilliant star Sirius serves as a landmark for locating this constellation. From May through September, Big Dog can be seen in the northern hemisphere.
Draco
Draco, a constellation in the northern hemisphere, can be seen not far from the Little Dipper and the Big Dipper asterisms in the constellation Ursa Major. This constellation stands out for its size, but lacks in brightness. In Greek mythology, it is considered a dragon, however, it is never specified which dragon it is.
A northern hemisphere viewer can see this constellation year-round. Following the North Star to the Big Dipper will lead you there. Between these two points is where the dragon’s tail finally reaches its end.
Crux
When seen from Earth’s southern hemisphere, the constellation Crux or commonly known as the Southern Cross becomes apparent in the night sky. Some nations, such as Australia and Brazil, include Southern Cross on their flags.
It’s a Latin cross made up of 4 identical stars. It can be seen in the springtime in the southern hemisphere, close to the constellation Centaurus.
Centaurus
The Centaurus constellation, like the Crux (the Southern Cross), can be seen from Earth’s southern hemisphere. Some of its stars are among the brightest in the sky, and the constellation itself is one of the biggest in the sky. A centaur, a mythical creature in Greek mythology that is half human and half horse, is shown here. Chiron, the eternal centaur, would have been the one to train Achilles and Heracles.
Because of its size and the number of stars it contains, this constellation can be difficult to see. A southern viewer can notice it with the aid of the Crux, which is similarly near and can be followed more easily in its totality.
How many constellations are there?
There are 88 distinct constellations officially recognized by the International Astronomical Union. In 1930, astronomer Eugene Delporte compiled the list of constellations we use today. The basic idea is to divide up the night sky into several shapes that include all of the visible stars. These somewhat distinguishable forms make it possible to identify individual stars. Although Greek mythology is the most common source for these depictions, many civilizations have adopted the practice of depicting and naming objects in the night sky.
Until the Renaissance, astronomers had only a limited understanding of the night sky, focusing on the constellations that could be seen from the northern hemisphere, and, more specifically, the part of the sky that could be seen from the Mediterranean coast. They are known as the boreal constellations. To achieve their goal of ocean conquest, explorers uncovered the southern constellations, which are only visible from the southern hemisphere.
In the 5th century B.C., the constellations of the zodiac were finalized. The ecliptic plane is the path along which Earth and the other planets of the solar system travel as they orbit the Sun. If you extend this plane, you’ll find a ring of 12 constellations there; this is because, as viewed from Earth, the Sun and the other planets always seem to be in one of these constellations.
Map of the 88 constellations
There are officially 88 constellations in the sky, as recognized by the International Astronomical Union. Borders define the regions inhabited by the constellations, allowing us to create an accurate sky map.
How to spot the constellations?
Without the proper equipment and clear skies, seeing the constellations may be a frustrating exercise. This means that the best location to look for them is somewhere with little ambient light and a dark sky. You can make use of the stars that are lower in the sky if you find yourself in a spot like this.
Obtain a sky map, such as the one found on SkyView, that can tell you which constellations may be seen at your current location and time. The SkyView app for smartphones can be used to determine which constellations are visible from a certain location.
Ursa Major is the starting point. Invariably located toward the North Star, this pan (the Big Dipper) has become a popular icon. It is part of the Little Dipper and aligns with the Big Dipper’s pan’s handle stars. Using these two, you can see other constellations, such as Draco, which lies between the two. Cassiopeia, with its distinctive W shape, can be seen on the sky’s other side from the North Star, opposite Ursa Major.
And don’t forget to train your eyes to spot Orion by its three dazzling shoulder stars. Taurus, which lies just above it, and Gemini, which is close to Orion’s elevated arm, are two constellations that can be easily recognized using this technique.
When you learn to identify these “important constellations,” along with the aid of a map or an app, you will be able to recognize and learn about many more constellations.
The reference constellation for observing the Milky Way
If light pollution isn’t too bad, the Milky Way can be seen clearly in the sky. In any case, the constellations can help you find the center of the galaxy. Only visible between mid-April and mid-September, during the summer months, this region of concentrated starlight lies between the constellations of Sagittarius and Scorpius and is very brilliant.
What are the northern constellations?
Those constellations known as the “northern constellations” can be seen from Earth’s northern hemisphere. They are the first western constellations to have been named by Greek astronomers. Ursa Major, Andromeda, and Cassiopeia are just a few examples.
What are the southern constellations?
Explorers who ventured into the southern hemisphere uncovered constellations that were obscured or invisible to those living in the northern hemisphere. Slowly but surely, they joined the list of northern constellations that had previously been recognized. The Carina, Centaur, and Crux are all examples of such constellations.
The 12 constellations of the zodiac
There are 12 zodiac constellations. Those constellations are located on the ecliptic’s elongation, or the plane in which the solar system’s eight planets orbit the sun.
Is Ophiuchus a genuine constellation?
Although Ophiuchus (also known as Serpentarius) is a real constellation, it is not often considered to be part of the zodiac. The mismatch between astrology and astronomy is the source of the surprise caused by the recall of the 13th constellation of the zodiac.
The zodiac constellations are those that the Sun, as viewed from Earth, travels through in the course of a year. Keep in mind that, while it seems that our star is moving in relation to Earth, it is really the Earth that rotates around the Sun. So, the Sun travels through 13 constellations in a year.
When the Babylonians codified the zodiacal constellations, they split this heavenly ring into 12 sections, each 30 degrees in length. Whether it was for ease of computation or so that one constellation might represent each month of the year, the decision ultimately resulted in the exclusion of Ophiuchus from the calendar used at the time.
But astronomers do recognize this constellation, and NASA clarifies that the zodiac signs have nothing to do with science but rather with astrology. According to the U.S. space agency, “astronomers and other scientists know that the stars, located many light years away, have no effect on the ordinary activities of humans on Earth.”
