"In the silent depth of space,
The Pleiades are a true physical star cluster of related stars in close proximity (as stellar distances go). Their common proper motion though space produces an apparent motion relative to Earth of approximately five seconds of arc per century in a south-easterly direction towards the star Lambda Tauri, and are thus traversing one degree across Earth's sky relative to the fixed stars every 60,000 years. Ranging from third to sixth visual magnitude, all nine of these brightest stars are visible to the unaided human eye, but most people report seeing 6 to 8 under less than ideal conditions. Some acute observers report being able to discern up to a dozen or more naked eye stars of the Pleiades cluster under dark skies. With the aid of binoculars dozens of dimmer members of the cluster come into view and a telescope reveals hundreds. Alcyone is the brightest star in the Pleiades, a type B (white blue) spectral class giant main sequence star with a mass exceeding 10 times and an absolute luminosity exceeding 1000 times that of our Sun. The approximately 380 light-year distance of the Pleiades star cluster reduces Alcyone's brightness to 2.87 visual magnitude in Earth's night sky. The Pleiades is moving through a vast cloud of interstellar dust which reflects the light of its stars. Though not visible to the unaided eye, extended photographic exposures show this reflection nebula enmeshing the Pleiades. The nebula is particularly bright around Merope although Alcyone carries her own stately blue aura. The most prominent stars of the Pleiades cluster are deeply rooted in ancient astronomies and mythologies, which has no doubt profoundly influenced the New Age movement's embodiment of beings from the Pleiades as a source of metaphysical power and enlightenment. Before the solar calendar was developed, the Pleiades marked the beginning of the year with their rise in the morning skies and the beginning of winter at their appearance in the evening. Within the Great Pyramid at Giza a tunnel directed toward the south corresponded precisely to the height of the meridian of the Pleiades whose passing through that opening, at midnight, marked the beginning of the year. The 9 brightest stars of the Pleiades were named by the ancient Greeks after seven sisters (Alcyone, Asterope, Celaeno, Electra, Maia, Merope, and Taygeta) and their father, the Titan Atlas, and Nymph mother, Pleione. According to one classical Greek myth, the seven virgin sisters were traveling with their mother when they encountered the giant Orion, a handsome hunter who was arrogant and self-possessed. Orion became enamored with Pleione and her daughters and began chasing after them trying to win their affections and favor. Pleione and her daughters prayed to the Gods for relief from Orion's unappreciated advances and eventually the great God Zeus intervened and transformed the seven sisters into doves to facilitate their escape from Orion. The doves flew into the sky to become stars of the Pleiades, which are relentlessly pursued through the night sky by the constellation Orion to this day. Hippocrates divided the year into four seasons determined by the position of the Pleiades in relation to the Sun: winter beginning with the setting of the Pleiades and ending with the spring equinox, spring lasting until the rising of the Pleiades, summer from their appearing to the rising of Arcturus, and the autumn until their setting again. Many Greek temples were oriented to the Pleiades, some for their rising including the Parthenon and Hecatompedon. Some Temples were oriented toward their setting such as the temple of Bacchus in Athens, Ascelpieion at Epidaurus and Sunium. When a star or planet rises just before the sun, it is called "heliacal rising," a situation observed closely by ancient astronomers. The Greek mariners of antiquity watched for the heliacal rising of the Pleiades to mark the opening of the sailing season in the Mediterranean and its setting the close for navigation. Caesar made the heliacal rising of the Pleiades begin the Julian summer and their setting the commencement of winter.
The Aztecs believed they could prevent the demons of darkness from descending to Earth and devouring them by offering human sacrifices to their Gods. During the sacrifice ceremony, the Aztec priests would anxiously watch the passage of the Pleiades across the celestial meridian at midnight, just subsequent to removing their sacrificial victims' still beating hearts. The overhead crossing of the Pleiades signaled the cosmos would not interrupt their movement and the world was not ending then, another fifty-two years of existence thus secured. At that specific moment, the Aztec priests would start fires on the slashed chests of the sacrificial victims. The fire was then carried to the temple of the Sun God Huitzilopochtli and to the homes of the Aztec people for their hearths. The Western Mono Indians, a Uto-Aztecan culture, apparently embraced a somewhat less ominous cosmology than the Aztecs. They saw in the Pleiades six wives who ate onions and were thrown out of their huts by angry husbands. According to their legend, the shunned wives wandered off to the sky and became the Pleiades. Later the husbands felt lonely and sorry and looked for their wives, but they were never found again. Other cultures have variously mythologized the Pleiades as a hen with chicks, little eyes, and harvest baskets to hold the autumn bounty. The Pleiades stars are very young on the cosmic scale of existence. Astronomers recently believed the cluster to be a stellar nursery not older than 20 million years with some of the members a young as 2 million years. But an increasing body of contemporary scientific observations and refinements in stellar evolution models indicate an age of approximately 100 million years for the Pleiades, which corresponds to Earth's Middle Cretaceous Period of the Mesozoic Era. Even at 100 million years of age, Alcyone and her stellar siblings are only about 1/40th the age of the Earth. At the time the thermonuclear fires of Alcyone were first igniting 100 million years ago, life had previously existed on Earth for several billion years. Contemporary with the birth of the Pleiades, flowering plants were undergoing their first evolutionary radiation and the Hadrosaurs ("duck billed" dinosaurs) were making their first appearance on Earth.
Due to her great mass Alcyone is much hotter than less massive and more typical main sequence stars such as our Sun. Her significantly higher core pressure and temperature are causing Alcyone to burn through her nuclear fuel much faster than Sol in spite of her larger size. Alcyone is more than 1000 times as luminous as Sol because she is burning up at a corresponding rate. Both Alcyone and Sol are currently on the main sequence, a stable, self regulating state where gravity (=> heat) and gas pressure (=> size) are at equilibrium. While on the main sequence, if its temperature increases/decreases, a star swells/shrinks due to the resultant increase/decrease in gas pressure. The swelling/shrinking increases/decreases the area of its radiating surface which in turn cools/heats the star. Our Sun will continue to burn in this stable state on the main sequence for several billions of years more before it ultimately evolves into a white dwarf star which will slowly cool and dim out as the last of its helium fuel is converted into carbon.
Alcyone is more rapidly headed towards a different and spectacular fate. She is going to blow up. Alcyone's mass and core temperature are so high that unlike Sol sized and smaller stars, she will continue fusing carbon at her core and transmute those fusion products into yet heavier elements such as oxygen, neon, magnesium, sulphur, and silicon until Alcyone finally begins fusing lighter elements into iron 56 at her core. Once Alcyone's core fuses its way down the nuclear transmutation chain to iron 56, it won't go any farther because iron 56 has the highest binding energy per nucleon of any element and fusion or fission of it requires energy input as opposed to releasing it. So the iron core will continue to accumulate until it reaches a critical mass of about 1.4 solar masses aka the "Chandrasekhar Limit", at which point the electron degeneracy pressure supporting the core against gravity will give up the ghost and Alcyone's core will collapse.
The remaining matter in Alcyone's neutron core will continue to collapse until a new equilibrium state known as neutron degeneracy is reached, where the quantum mechanical repulsive force between the neutrons reaches equilibrium with the gravitational force. Alcyone will become a neutron star pulsar at the center of a great explosion nebula similar to the Crab Nebula in Orion. Neutron stars are one of the most exotic objects in the Universe, being so dense a marble sized piece of one would weigh one hundred million tons on Earth. If the matter remaining in her core after Alcyone supernovas exceeds several solar masses, Alcyone will continue to collapse through the neutron star stage and into a black hole. In that case Alcyone will effectively leave our physical universe, leaving only the metaphysical ghost of her gravity behind...
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Alcyone is named after a star in the Pleiades, a galactic star cluster which passes through our skies in the constellation Taurus and is undoubtedly the most familiar star cluster to mankind. At approximately 380 light years distant, it is one of the nearest galactic clusters to Earth. The brightest orbs of the Pleiades consist of nine white blue stars concentrated in a region about 7 light years across, although the entire cluster occupies a greater volume of space approximately 30 light years in diameter.
Many other ancient cultures developed their own mythologies regarding the Pleiades, whose positions on the celestial sphere coincide with the beginning and ending of agricultural as well as navigational seasons. The Pleiades were known to the Aztecs as Tianquiztli, which means the "marketplace." Their calendar was based on cycles of fifty-two years. At the end of each fifty-two year cycle, a major religious ceremony was held to ensure the movement of the cosmos and the rebirth of the Sun.
Alcyone is actually the primary of a compact multiple star system. She is closely orbited by a companion which is itself a trinary system of three lower magnitude stars. The brightest of Alcyone's three companions is 24 Tau (HD 23629), a type A (white) spectral class star with a visual magnitude of 6.3. The second brightest companion in the trinary system orbiting Alcyone is V647 Tau (HD 23607), another type A (white) spectral class star with a visual magnitude of 8.3. The dimmest companion is HD 23608, a G (yellow) spectral class star with a visual magnitude of 8.7.
At the extremely high pressures involved in this collapse, the protons and electrons in Alcyone's core will be crushed together to form neutrons, liberating great quantities of highly energetic neutrinos during the process. Alcyone's outer layers will follow its collapsing core inward and their high density at this stage of the gravitationally induced collapse will trap the neutrinos, which will in turn push Alcyone's outer layers away from her core with fantastic force. The resulting shock wave will blow off Alcyone's outer layers in a tremendous supernova explosion, leaving only her neutron core behind.