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Individual young stars are correlated in position too. Gomez et al. (1993) studied the 2-point correlation function for stars in the local star-forming region Taurus. For 121 young stars, there was a power law distribution of the number of stars as a function of their separation, which means that the stars are hierarchically correlated. (A similar correlation might arise from an isothermal distribution of stars without any hierarchical structure, as in a relaxed star cluster, but the Taurus region is not like this.) The correlation in Taurus extended from 0.15" of arc separation to at least 2° separation - nearly 3 orders of magnitude. Larson (1995) extended this survey to smaller scales and found a break in the correlation at 0.04 pc. He suggested that smaller scales formed binary stars by fragmentation in clumps, and larger scales formed hierarchical groups by gas-related fragmentation processes, including turbulence.

Low mass x-ray stars in Gould's Belt (i.e., T Tauri stars) show a hierarchical structure in all-sky maps (Guillout et al. 1998). This means that large groupings of T Tauri stars contain smaller sub-groupings and these contain even smaller sub-sub groupings. This is a much bigger scale than the Taurus region studied by Gomez et al. (1993). There has been no formal correlation of the large-scale structure in x-ray stars yet. The all-sky coverage suggests that the Sun is inside a hierarchically clumped complex of young stars.