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Sun. The Sun is the star at the center of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light and infrared radiation with 10% at ultraviolet energies.
720,000 km/h (450,000 mi/h) [10] Orbital period. ~230 million years [10] The Solar System[d] is the gravitationally bound system of the Sun and the objects that orbit it. [11] It was formed about 4.6 billion years ago when a dense region of a molecular cloud collapsed, forming the Sun and a protoplanetary disc.
Taken on 20 October 1968 from Apollo 7. Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere as daylight when the Sun is above the horizon.
v. t. e. Sunspots are temporary spots on the Sun's surface that are darker than the surrounding area. They are regions of reduced surface temperature caused by concentrations of magnetic flux that inhibit convection. Sunspots appear within active regions, usually in pairs of opposite magnetic polarity. [2] Their number varies according to the ...
The position of the Sun in the sky is a function of both the time and the geographic location of observation on Earth 's surface. As Earth orbits the Sun over the course of a year, the Sun appears to move with respect to the fixed stars on the celestial sphere, along a circular path called the ecliptic. Earth's rotation about its axis causes ...
Symbol. M☉. In SI base units. 1.988 416 × 1030 kg[1] The solar mass (M☉) is a standard unit of mass in astronomy, equal to approximately 2 × 1030 kg. 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.
Sun path, sometimes also called day arc, refers to the daily and seasonal arc -like path that the Sun appears to follow across the sky as the Earth rotates and orbits the Sun. The Sun's path affects the length of daytime experienced and amount of daylight received along a certain latitude during a given season.
After Ribas (2010) [1] The solar luminosity (L☉) is a unit of radiant flux (power emitted in the form of photons) conventionally used by astronomers to measure the luminosity of stars, galaxies and other celestial objects in terms of the output of the Sun. One nominal solar luminosity is defined by the International Astronomical Union to be 3 ...