Glossary term: Pleiades

Description: The Pleiades is a cluster of stars in the constellation of Taurus. An open cluster of over a thousand stars, the Pleiades is about 440 light years from Earth. The Pleiades is relatively young by astronomical standards with an age estimated to be within 70–150 million years. Between six and nine members of the Pleiades are visible with the naked eye under most conditions.

As a prominent stellar cluster the Pleiades has a wealth of mythology and folklore associated with it from cultures across the globe. Its first appearance in the morning sky is an important marker in the calendars of several societies, including signaling the Māori New Year. The name "Pleiades" comes from the Greek legend associated with the cluster.

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Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".

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The bow tie shaped Orion over dry, rocky outcrops. Sirius appears as a bright star between two pillars of rock

Winter Constellations

Caption: Second place in the 2022 IAU OAE Astrophotography Contest, category Time lapses of celestial patterns.   Sirius, the brightest star in the night sky, is shown rising, setting and passing by. Sometimes constellations and asterisms are also visible, including Orion, Taurus and the Pleiades. In the first scene, the aforementioned constellations are covered by a semi-transparent golden veil. The next scenes show it rising in a dark blue night sky. In one of the scenes, a planet brightly decorates the faint constellation Pisces. The videos were taken above various landscapes and places of cultural heritage on Earth. Some of them simply show monuments in the desert, while others show palm trees with waving leaves.
Credit: Amirreza Kamkar/IAU OAE

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In front of the curve of the Milky Way we find the hourglass-shaped Orion and the bright Pleiades star cluster.

Warm Winter Night Over Spiš Region

Caption: Winner in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns.   This image, taken in Slovakia in January 2022, shows regions of the Milky Way and a rich variety of constellations. The summer constellations of the northern hemisphere are very low in the sky towards the bottom-right. The bright stars of Cygnus and Lyra shine through the artificial lights at the horizon. The huge array of northern winter and autumn constellations with many bright stars are associated with diverse cultural stories. For the Lakota people in North America the belt of the Orion constellation represents the spine of a bison (“Tayamnicankh”). Orion, the Hunter of Greek mythology, is sometimes described chasing the Seven Sisters, the Pleiades. The Arabs transformed this view by considering the follower of the Pleiades only one star instead of a constellation. Aldebaran, the star in the right eye of Taurus, the Bull, comes from this interpretation, because the name Aldebaran derives from al-dabaran, The Follower. At the bottom-right, on the horizon, we can see the milky lightcone of the Zodiacal light stretching from the constellation Pisces through Aries, almost reaching the Pleiades, indicating the path of the planets and the Moon in this area. The Pleiades and the Hyades together form a gate on this path, where the heavenly bodies occasionally pass before entering the Milky Way. The planets were considered sheep in ancient Babylon and the modern constellation Orion was considered the “True Shepherd” of the Sky, with his shepherd’s tool reaching the ecliptic. In Roman tradition, the bright white star above the Pleiades and the Milky Way is called Capella, the Goat, which can be traced back to an Egyptian constellation in this area. Above the treetop in the middle-right part of the image, we see the autumn square, the Andromeda Galaxy and the W-shaped pattern of Cassiopeia. To the left of this group, in the central part of the visible Milky Way, is the constellation Perseus, with Cepheus in the dark area above Cassiopeia completing the celestial family. The Andromeda saga is a Greek story from the area that is now called Israel, and is rooted in Syrian traditions. The location of Andromeda was considered by the ancient Babylonians as the location of the goddess of sexual love, and by the Syrians as the location of the goddess of fertility. According to the saga, Andromeda was chained to a rock at the coast of Jaffa (Tel Aviv) in order to protect her land from a sea monster. The name of the hero who rescued her is Perseus, probably meaning “from Persia” (today’s Iran). Noticeable in the valley are the lights from towns. The yellow light above the horizon indicates larger cities there, which are given away by their light pollution.
Credit: Robert Barsa/IAU OAE

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The crescent Moon sits to the left of two bright planets. On the right side the Pleiades star cluster can be seen.

Moon-Mercury-Pleiades Conjunction

Caption: Honourable mention in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns.   This photograph shows the young lunar crescent, some of the nine brightest stars of the Pleiades (with one behind a cloud) on the right, and the planet Mercury, looking slightly red, in the middle of the image. This picture is rather suggestive of the idea that the Pleiades might possibly consist of seven stars. However, the viewer is misled by the clouds; five of the stars form a tiny chariot, one is next to the handle, and three are at the other end of the quadrilateral. Eight stars would be clearly visible if there were no clouds. This configuration of the young Moon next to the Pleiades is visible only in the northern hemisphere spring. Thus it was used by the ancient Babylonians to determine the second month of their year and to judge whether or not an intercalary month was necessary. At least as early as the second millennium before the common era, the Babylonians used several asterisms for each month, with another one of them reappearing every five days after invisibility during daylight. To determine the necessity of intercalation in order to synchronise the solar and the lunar year, the Babylonians used several asterisms, not only the Pleiades. For instance, they also made use of the bright stars Arcturus and Sirius, and they observed a configuration with the Moon as well as heliacal phenomena. The modern Jewish and modern Islamic traditions still make use of some of the Babylonian astronomical rules. However, given that the constellations have shifted as a result of precession, and the fact that nowadays we also have computational means to calculate our calendars, this configuration of the small crescent Moon and the Pleiades is less useful, though it remains exceptionally beautiful. Thus the ancient Babylonian and middle Babylonian tradition survives only rudimentarily. Furthermore, it is unlikely that it is depicted in the Nebra Disc from Bronze Age Europe, as has long been claimed. This image was taken on Elba Island, Italy, in May 2022.
Credit: Giulio Colombo/ IAU OAE

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A cluster of brilliant blue stars illuminate the surrounding nebular gas.

The Pleiades M45 with Majestic Dust

Caption: Honourable mention in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns.   Taken in Dar Eid in Saint Catherine/Sinai, Egypt, in October 2021, this image shows the Pleiades, an open cluster also known as The Seven Sisters. The Pleiades are located in the north-western part of the constellation Taurus, the Bull. This constellation originates from ancient Babylonian or even Sumerian belief, where it was designated the Bull of Heaven, a mighty creature owned by the sky god. In Late Babylonian times, the Pleiades were called The Bristle at the hunchback of The Bull. In China, the asterism is also called The Hair, but this does not necessarily imply any relationship between the East Asian and West Asian names of this asterism, although exchange is hypothesised with the establishment of the Silk Road. In ancient Babylonian texts the term The Hair does not appear. Instead, the Pleiades are only called The Star Cluster in Sumerian, and the Sumerian term was used in later languages as a loanword. The Sumerian and early Babylonian religion associated all constellations with specific deities, including gods, demons, messengers of gods. The Star Cluster was associated with a deity of the Netherworld that was called The Seven and was considered an ensemble of seven speaking weapons or strongly armed gods. The later Greek name of the Seven Sisters might possibly have sprung from an intercultural misunderstanding of this older religious association, since, in fact, seven stars are not seen in this cluster. The star cluster of the Pleiades is really prominent in the sky, and thus was used for several cultural purposes, such as determining the calendar and the spring equinox. However, its significance is frequently overstated in cultural astronomy. As the tradition of representing it with seven dots originates from an ancient Sumerian belief, we should be careful about interpreting any group of seven dots on cave walls and archaeological sites across Europe, Asia and America from the Stone Age onwards as a representation of the Pleiades. Modern astrophysics has found that the star cluster of the Pleiades is extraordinarily young, so there was certainly not an additional star in ancient times. Furthermore, we know that the bright stars are only the core region of an open star cluster that consists of hundreds of stars scattered over an area of the sky which exceeds the bright core by one or two of its diameters in any direction. The photograph does not even show the whole cluster. The group is thought to be about 400 light-years away from Earth, which is relatively close in astronomical terms.
Credit: Mohamed Usama/IAU OAE

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Orion appears as an hourglass shape of stars in the bottom of the image. Above Taurus is v-shaped with a small star cluster

Romanian Orion

Caption: Winner in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns.   Taken in Romania in August 2012, this image shows two of the most recognisable constellations in the sky, Orion and Taurus. Orion, the Hunter, is found near the horizon. The most prominent star visible in this image is Betelgeuse, while the asterism of Orion’s belt is formed by three aligned bright stars. Just above Orion we can find Taurus, one of the constellations of the Zodiac. As the Zodiac is inherited from Babylon, The Bull of Heaven represents a mighty but dangerous creature that was defeated by King Gilgamesh and his friend Enkidu. They cut the Bull in half and sacrificed the animal to the gods in order to protect their people. Taurus is also home to the star cluster Pleiades, also known as the Seven Sisters. Two planets are visible: Venus, the bright spot near the fence, and Jupiter, the bright spot at the top, next to the Bull’s face. Different cultures have included the stars of these constellations in their own mythology. The Romanians, for instance, after Christianisation identified four other constellations using some of the stars of Orion and others surrounding it. One such constellation is called Trisfetitele (the Three Saints), which is associated with the three stars comprising Orion's Belt, representing the Three Hierarchs Basil, Gregory and John. This same asterism is also called Three Wise Men, Kings from the East or just Three Kings — all of these names being rooted in the Christian religion. The agricultural calendar, in contrast, led farmers to define two other constellations, the Little Plough and the Sickle. Both are seen in the southern half of the Orion rectangle; the Little Plough is drawn by connecting the southern quadrilateral with Orion’s left shoulder, and the Sickle is formed by connecting Orion’s left foot (Rigel) with the belt stars, forming an arch and completing the form of a hoe. In the cultural calendar, these constellations were used to announce the harvest of wheat/grain. Finally, the fourth Romanian constellation is the Great Auger, where Orion’s belt represents the handle of the auger, and Betelgeuse is the tip, facing towards Pollux in Gemini. This constellation is associated with treasure, as Romanian peasants believe that the Auger points to the treasure when they approach the end of the world. Most of the official star names in Orion are Arabic; Mintaka (meaning “belt”) is at the waist; Alnitak (meaning “girdle”) and Alnilam (meaning “string”) are at the belt; and Rigel (meaning foot) is at the left foot. The star on the left shoulder is named Bellatrix, the Latin term for a female warrior. The star at the right leg is called Saiph, for the sword or sabre of the Arabic Orion.
Credit: Alex Conu/IAU OAE

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The bright, diffuse Milky Way, interrupted by mottled dark patches, arches over a wintry landscape.

Winter Milky Way

Caption: Winner in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns.   Taken near Lake Misurina in the Veneto region of Italy in February 2019, this image shows a clear and starry sky over a winter landscape. We can see part of the Milky Way arc. From the left side, towards the south-east, we see Sirius, "The Burner" in Greek, the brightest star in the night sky. It is part of the constellation Canis Major, The Great Dog, one of the dogs of Orion, the great hunter, in Greek mythology. Orion’s other dog, Canis Minor, the Small Dog, is represented by the bright star Procyon and its fainter neighbours. The Greek star name means “The One [rising] before The Dog” and the star is seen at the top left side of the image just above the arc of the Galaxy. Orion lies to the right of Canis Major. We can spot its characteristic “belt”, an asterism composed of three bright stars aligned in a straight line.  Above the treetops to the right of Orion, the open star clusters of the Hyades and the Pleiades in the constellation Taurus, the Bull, are visible. According to ancient lore, these two clusters form a Celestial Gate directly next to the intersection of the great circles of the ecliptic and the Milky Way. In Greco-Roman mythology, Taurus is associated with the god Zeus who is said to have used a bull to seduce the Phoenician princess Europa. Above the constellation Taurus, we can see a bright star just above the arc of the Galaxy. This is Capella, the brightest star of the constellation Auriga, The Charioteer. This is one of the 88 modern constellations and is associated with the Greek hero Erichthonius of Athens. Hindu astronomy considers Capella as the heart of Brahma, one of the three major gods. The indigenous people of Bororo in Brazil have a constellation representing a cayman, comprising some of the stars of Auriga and some stars from neighbouring constellations. To the right of Taurus, we find the modern constellation Perseus with the bright double star cluster h+chi Perseii, which represents the metal of Perseus’s sabre in Greek mythology. Perseus is the hero who was sent out to prove himself, and happened to rescue Andromeda from the sea monster Cetus as the Roman poet Ovid wrote. We can also see the constellation Cassiopeia, associated with the queen and mother of Andromeda in Greek mythology. It is composed of five bright stars in the shape of a W, which was considered the asterism of The Key by the Greeks according to the poet Aratus. The recognisable shape is also associated with other mythologies: for instance, it represents the princess Sharmishtha in Hindu astronomy, a bat in Thailand, and a camel in native Arabic astronomy. In the gap between the trees, the Andromeda Galaxy is visible.
Credit: Giorgia Hofer/IAU OAE

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A montage of images of Mars, seen here as a series of red dots in a squashed z-shaped pattern.

Retrograde Motion of Mars

Caption: This image captures the celestial waltz of Mars as it demonstrates its intriguing retrograde motion against the background of fixed stars. This event, when Mars appears to backtrack in its orbit, arises from the different speeds at which Earth and Mars orbit the Sun. Earth’s faster movement occasionally positions it ahead of Mars, creating the illusion of the Red Planet moving in reverse from our perspective. This retrograde motion occurs when Mars is on the other side of the sky from the Sun, when it is said to be in opposition. Following Mars from 14 August 2022 to 5 April 2023, this smartphone image stands as a testament to perseverance and precision in the tranquil setting of Bataan, Philippines. Enduring unpredictable weather and ever-shifting celestial alignments, the photographer meticulously captured each shot at regular intervals of five to eight days. The process involved aligning 35 distinct images of Mars, taken without any external lens or telescope, alongside a stacked background image composed of 54 frames lasting 15 seconds each, portraying the starry expanse. Fusing these images involved precisely aligning them and cropping Mars in order to centre its position, revealing its retrograde movement against the backdrop of stars. This intricate process, blending the images seamlessly into the background by masking, highlights the planet’s unique motion. In the lower right corner, the Pleiades star cluster is visible.
Credit: Rob Kerby Guevarra/IAU OAE (CC BY 4.0)

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