who discovered the above mentioned clusters?
Abraham Ihle
Globular cluster
The first known globular cluster, now called M 22, was discovered in 1665 by Abraham Ihle, a German amateur astronomer. 
some globular clusters have three main sequence tracks. this indicates UNANSWERABLE what is this cluster? It is a spherical collection of stars that orbits a galactic core. how is this clusters formed? The formation of globular clusters remains a poorly understood phenomenon and it remains uncertain whether the stars in a globular cluster form in a single generation or are spawned across multiple generations over a period of several hundred million years. what are this composed of? Globular clusters are generally composed of hundreds of thousands of low-metal, old stars. what are its exotic components? Some exotic classes of stars, such as "blue stragglers", "millisecond pulsars", and "low-mass X-ray binaries", are much more common in globular clusters. what is the first one? A blue straggler is a main-sequence star in an open or globular cluster that is more luminous and bluer than stars at the main sequence turnoff point for the cluster. are there any other types of it? "Yellow stragglers" or "red stragglers" what is meant by the second exotic class? It is a pulsar with a rotational period smaller than about 40 milliseconds. what can you tell me about its rotation speed? one X-ray pulsar that spins at 599 revolutions per second
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Globular cluster [SEP] Observation history
He coined the term "globular cluster" in his "Catalogue of a Second Thousand New Nebulae and Clusters of Stars" published in 1789. The number of globular clusters discovered continued to increase, reaching 83 in 1915, 93 in 1930 and 97 by 1947. A total of 152 globular clusters have now been discovered in the Milky Way galaxy, out of an estimated total of 180 ± 20. These additional, undiscovered globular clusters are believed to be hidden behind the gas and dust of the Milky Way.