which organization controls it?
General Conference on Weights and Measures (CGPM)
International System of Units
The SI was established and is maintained by the General Conference on Weights and Measures (CGPM).
characteristics of stars based on the characteristics of the sun A star with mass greater than 0.4 times the Sun's will expand to become a red giant when the hydrogen fuel in its core is exhausted. have these been observed since ancient times? UNANSWERABLE how are they measured? It is often most convenient to express mass, luminosity, and radii in solar units could you please explain the second term? It is an absolute measure of radiated electromagnetic power, the radiant power emitted by a light-emitting object. howe is it measured? In SI units, luminosity is measured in joules per second, or watts and in astronomy, in the terms of the luminosity of the Sun, L how is it measured for a star? By its size in terms of solar radii, R, and effective temperature in kelvins what is this last unit that you mentioned? It is the base unit of temperature in the International System of Units (SI) why was it redefined? So that Boltzmann constant takes the exact value by whom was this unit formulated? William Thomson, later ennobled as Lord Kelvin you mentioned about an international system earlier, what is it? It is the modern form of the metric system; only system of measurement with an official status in nearly every country in the world. when was it introduced? 1960
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International System of Units [SEP] Controlling body
The SI was established and is maintained by the General Conference on Weights and Measures (CGPM). In practice, the CGPM follows the recommendations of the Consultative Committee for Units (CCU), which is the actual body conducting technical deliberations concerning new scientific and technological developments related to the definition of units and the SI. The CCU reports to the International Committee for Weights and Measures (CIPM), which, in turn, reports to the CGPM. See below for more details. All the decisions and recommendations concerning units are collected in a brochure called "The International System of Units (SI)", which is published by the International Bureau of Weights and Measures (BIPM) and periodically updated.