what is this last unit that you mentioned?
It is the base unit of temperature in the International System of Units (SI)
Kelvin
The kelvin is the base unit of temperature in the International System of Units (SI),
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
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Kelvin [SEP] Introduction
The kelvin is the base unit of temperature in the International System of Units (SI), having the unit symbol K. It is named after the Belfast-born Glasgow University engineer and physicist William Thomson, 1st Baron Kelvin (1824–1907). The kelvin is now defined by fixing the numerical value of the Boltzmann constant to 1.380 649×10 J⋅K. This unit is equal to kg⋅m⋅s⋅K, where the kilogram, metre and second are defined in terms of the Planck constant, the speed of light, and the duration of the caesium-133 ground-state hyperfine transition respectively. Thus, this definition depends only on universal constants, and not on any physical artifacts as practiced previously, such as the International Prototype of the Kilogram, whose mass diverged over time from the original value.