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There is often ongoing star formation in these clusters, so embedded clusters may be home to various types of young stellar objects including protostars and pre-main-sequence stars. An example of an embedded cluster is the Trapezium Cluster in the Orion Nebula .
In 1910 Hans Oswald Rosenberg published a diagram plotting the apparent magnitude of stars in the Pleiades cluster against the strengths of the calcium K line and two hydrogen Balmer lines. [3] These spectral lines serve as a proxy for the temperature of the star, an early form of spectral classification.
The path which the star follows across the HR diagram is called an evolutionary track. [57] H–R diagram for two open clusters: NGC 188 (blue) is older and shows a lower turn off from the main sequence than M67 (yellow). The dots outside the two sequences are mostly foreground and background stars with no relation to the clusters.
HR diagrams for two open clusters, M67 and NGC 188, showing the main sequence turn-off at different ages. The turnoff point for a star refers to the point on the Hertzsprung–Russell diagram where it leaves the main sequence after its main fuel is exhausted – the main sequence turnoff.
An open cluster is a type of star cluster made of tens to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, and many more are thought to exist. [1]
Sketch of Hertzsprung–Russell diagram of a globular cluster, showing blue stragglers. A blue straggler is a type of star that is more luminous and bluer than expected. . Typically identified in a stellar cluster, they have a higher effective temperature than the main sequence turnoff point for the cluster, where ordinary stars begin to evolve towards the red gi
The horizontal branch is so named because in low-metallicity star collections like globular clusters, HB stars lie along a roughly horizontal line in a Hertzsprung–Russell diagram. Because the stars of one globular cluster are all at essentially the same distance from us, their apparent magnitudes all have the same relationship to their ...
A multiple star system consists of two or more stars that appear from Earth to be close to one another in the sky. [dubious – discuss] This may result from the stars actually being physically close and gravitationally bound to each other, in which case it is a physical multiple star, or this closeness may be merely apparent, in which case it is an optical multiple star [a] Physical multiple ...