by whom was this unit formulated?
William Thomson, later ennobled as Lord Kelvin
Kelvin
In 1848, William Thomson, who was later ennobled as Lord Kelvin, wrote in his paper "On an Absolute Thermometric Scale" of the need for a scale whereby "infinite cold" (absolute zero) was the scale's null point, and which used the degree Celsius for its unit increment. Kelvin calculated that absolute zero was equivalent to −273 °C on the air thermometers of the time. This absolute scale is known today as the Kelvin thermodynamic temperature scale.
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
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Kelvin [SEP] History
In 1954, Resolution 3 of the 10th General Conference on Weights and Measures (CGPM) gave the Kelvin scale its modern definition by designating the triple point of water as its second defining point and assigned its temperature to exactly 273.16 kelvin. In 1967/1968, Resolution 3 of the 13th CGPM renamed the unit increment of thermodynamic temperature "kelvin", symbol K, replacing "degree Kelvin", symbol °K. Furthermore, feeling it useful to more explicitly define the magnitude of the unit increment, the 13th CGPM also held in Resolution 4 that "The kelvin, unit of thermodynamic temperature, is equal to the fraction of the thermodynamic temperature of the triple point of water."