Pleiades

The Pleiades is a nearby, young open star cluster in Taurus, visible to the naked eye. Its bright stars formed together from the same cloud of gas and dust.

Open cluster: A loosely bound group of stars formed from the same molecular cloud. The Pleiades is a nearby example of this kind of stellar group.
Gravitational binding energy: The energy required to disperse a gravitationally bound system into separate parts. The Pleiades’ modest binding helps explain why it will eventually disperse.
Alcyone: The brightest star in the Pleiades, a blue-white multiple-star system. It anchors the cluster’s central region and is its most prominent member.
Hertzsprung–Russell diagram: A plot comparing stars’ luminosities with their surface temperatures or colors. Its color–magnitude sequence helps astronomers estimate the Pleiades’ age and distance.
Stellar parallax: The apparent shift in a nearby star’s position caused by Earth’s motion around the Sun. Parallax provides a direct geometric route to measuring the cluster’s distance.
Taurus molecular cloud: A complex of dense interstellar gas and dust in the constellation Taurus. It is the region of star-forming material associated with the Pleiades’ birth.
Stellar kinematics: The measurement and interpretation of stars’ positions and motions. Members share coherent motions that help distinguish them from foreground stars.
Atlas (star): A bright multiple-star system in the Pleiades, traditionally named for the Titan Atlas. Together with Pleione, it forms the close pair at the cluster’s eastern end.
Pleiades age: The estimated time since the Pleiades’ stars formed, roughly 100 million years. Its youthful age distinguishes the cluster from older open clusters.
Main-sequence fitting: A method for estimating a star cluster’s distance by matching its color–magnitude sequence to a calibrated one. Astronomers use it to check distance estimates for the Pleiades.

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