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Pleiades

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The Pleiades is a famous open star cluster located in the northwest of the constellation Taurus.

M45map
M45map

It is also known by the names Seven Sisters or Messier 45 (M45). An open cluster is a group of stars that are physically related and held together by gravity. The Pleiades is one of the nearest star clusters to Earth. It sits at a distance of approximately 444 light-years. Because the stars are so bright, it is the most obvious star cluster visible to the naked eye. It remains easy to see even in areas with significant light pollution. This cluster is a vital part of our night sky and has been studied for thousands of years.

The cluster is dominated by hot, luminous blue stars. These stars are quite young, having formed within the last 100 million years.

Reflection nebula IC 349 near Merope
Reflection nebula IC 349 near Merope

Astronomers have observed reflection nebulae surrounding the brightest stars. These include the HII region NGC 1432 and the Merope Nebula, also known as NGC 1435. A reflection nebula is a cloud of dust that reflects the light of nearby stars. While scientists once thought this dust was leftover material from the stars' formation, they now believe otherwise. Current evidence suggests the stars are simply passing through an unrelated interstellar dust cloud. This dust cloud moves at a different speed than the stars in the cluster. Computer simulations suggest the Pleiades likely formed from a compact shape similar to the Orion Nebula.

The Pleiades has played a major role in human history and timekeeping. In the third millennium BC, around 2330 BC, the cluster marked the vernal point. The vernal point is the position in the sky where the sun crosses the celestial equator. Because of this, the cluster was essential for establishing ancient calendars. In ancient India, the cluster was called Kṛttikā, meaning "the Cuttings." This name refers to how the stars mark the break of the year. In Mesopotamia, the cluster was included in the MUL.APIN, an early astronomy treatise found at Nineveh. The Nebra sky disc from around 1600 BC also depicts the cluster.

Nebra Scheibe
Nebra Scheibe

This artifact shows the stars in a high position between the Sun and the Moon.

Many different cultures around the world have given the Pleiades unique names and meanings. In Greece, the name refers to seven divine sisters. This mythology often explains why only six stars might seem visible. In Japan, the cluster is known as Subaru, which means "to cluster together."

Subaru logo (transparent)
Subaru logo (transparent)

The cluster has been recognized by the Celts, the Maya, the Aztec, and the Cherokee. Indigenous Australians also have many traditions regarding these stars. In Hinduism, the stars are associated with the war deity Kartikeya and the Seven Mothers. Even the Bible mentions the cluster using its Hebrew name. These diverse names show how much the cluster has mattered to humanity.

Scientific understanding of the Pleiades grew significantly with the invention of the telescope. Galileo Galilei was the first astronomer to view the cluster through a telescope. In 1610, he published his findings in the treatise *Sidereus Nuncius*.

Pleiades Sidereus Nuncius
Pleiades Sidereus Nuncius

He discovered that the cluster contained many more stars than the naked eye could see. Later, in 1767, John Michell calculated the mathematical probability of the stars being a random alignment. He found the chance of such a bright alignment happening by accident was only 1 in 500,000. This helped prove the stars were physically related. In 1771, Charles Messier included the cluster in his famous catalogue of objects. He labeled it M45, a name that scientists still use today.

The cluster remains a significant subject in modern science and culture. The Subaru Telescope in Hawaii is named after the cluster. The Subaru automobile company also uses the cluster's name and a six-star logo.

Seven Sisters coin Royal Australian Mint 1 dollar 2020 Reverse
Seven Sisters coin Royal Australian Mint 1 dollar 2020 Reverse

In literature, J.R.R. Tolkien referred to the Pleiades as the Remmirath, or the netted stars. Astronomers also study the cluster's future. They estimate the Pleiades will survive for about another 250 million years. Eventually, gravitational interactions with the surrounding galactic neighborhood will cause the cluster to break apart. For now, it remains a bright and beautiful landmark in the heavens.

The Pleiades is also linked to other celestial structures. Together with the Hyades cluster, it forms the Golden Gate of the Ecliptic. The ecliptic is the path that the Sun appears to follow across the sky. This connection helps astronomers map the movement of objects within our galaxy. By studying the Pleiades, scientists learn more about how star clusters form and evolve. The movement of the stars and the surrounding dust provides clues about the interstellar medium. Every observation helps us understand the complex systems that make up our universe.

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🖼️ Images & Media (9)
File:Nebra Scheibe.jpg
Nebra Scheibe.jpg
File:Seven Sisters coin Royal Australian Mint 1 dollar 2020 Reverse.jpg
Seven Sisters coin Royal Australian Mint...
File:Pleiades Sidereus Nuncius.png
Pleiades Sidereus Nuncius.png
File:Subaru logo (transparent).svg
Subaru logo (transparent).svg
File:Astro 4D m45 cr anim.gif
Astro 4D m45 cr anim.gif
File:Stereogram guide cross-eyed.svg
Stereogram guide cross-eyed.svg
File:M45map.jpg
M45map.jpg
File:Pleiades-motion.png
Pleiades-motion.png
File:Reflection nebula IC 349 near Merope.jpg
Reflection nebula IC 349 near Merope.jpg
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