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The solar mass (M ☉) is a standard unit of mass in astronomy, equal to approximately 2 × 10 30 kg (2 nonillion kilograms in US short scale). It is approximately equal to the mass of the Sun. It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. More precisely, the mass of the ...
The Sun is 1.4 million kilometers (4.643 light-seconds) wide, about 109 times wider than Earth, or four times the Lunar distance, and contains 99.86% of all Solar System mass. The Sun is a G-type main-sequence star that makes up about 99.86% of the mass of the Solar System. [26]
The astronomical unit of mass is the mass of the Sun (S). The astronomical unit of length is known as the astronomical unit ( A or au ), which in the IAU(1976) system is defined as the length for which the gravitational constant , more specifically the Gaussian gravitational constant k expressed in the astronomical units ( i.e. k 2 has units A ...
The solar mass (M ☉), 1.988 92 × 10 30 kg, is a standard way to express mass in astronomy, used to describe the masses of other stars and galaxies. It is equal to the mass of the Sun, about 333 000 times the mass of the Earth or 1 048 times the mass of Jupiter.
For example, the atomic mass constant is exactly known when expressed using the dalton (its value is exactly 1 Da), but the kilogram is not exactly known when using these units, the opposite of when expressing the same quantities using the kilogram.
The choice of solar mass, M ☉, as the basic unit for planetary mass comes directly from the calculations used to determine planetary mass.In the most precise case, that of the Earth itself, the mass is known in terms of solar masses to twelve significant figures: the same mass, in terms of kilograms or other Earth-based units, is only known to five significant figures, which is less than a ...
In modern academic writing, the Sun symbol is used for astronomical constants relating to the Sun. [10] T eff☉ represents the solar effective temperature, and the luminosity, mass, and radius of stars are often represented using the corresponding solar constants (L ☉, M ☉, and R ☉, respectively) as units of measurement. [11] [12] [13] [14]
This is because the distance between Earth and the Sun is not fixed (it varies between 0.983 289 8912 and 1.016 710 3335 au) and, when Earth is closer to the Sun , the Sun's gravitational field is stronger and Earth is moving faster along its orbital path. As the metre is defined in terms of the second and the speed of light is constant for all ...