The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields. It has a diameter of about 1,392,684 km, about 109 times that of Earth, and its mass (about 2×1030 kilograms, 330,000 times that of Earth) accounts for about 99.86% of the total mass of the Solar System. Chemically, about three quarters of the Sun's mass consists of hydrogen, while the rest is mostly helium. The remainder (1.69%, which nonetheless equals 5,628 times the mass of Earth) consists of heavier elements, including oxygen, carbon, neon and iron, among others.
The Sun formed about 4.6 billion years ago from the gravitational collapse of a region within a large molecular cloud. Most of the matter gathered in the center, while the rest flattened into an orbiting disk that would become the Solar System. The central mass became increasingly hot and dense, eventually initiating thermonuclear fusion in its core. It is thought that almost all other stars form by this process. The Sun's stellar classification, based on spectral class, is a G-type main-sequence star (G2V), and is informally designated as a yellow dwarf, because its visible radiation is most intense in the yellow-green portion of the spectrum and although its color is white, from the surface of the Earth it may appear yellow because of atmospheric scattering of blue light. In the spectral class label, G2 indicates its surface temperature of approximately 5778 K (5505 °C), and V indicates that the Sun, like most stars, is a main-sequence star, and thus generates its energy by nuclear fusion of hydrogen nuclei into helium. In its core, the Sun fuses 620 million metric tons of hydrogen each second.
The colour orange takes its name from the orange fruit. On the spectrum of light, and in the traditional colour wheel used by painters, it is located between red and yellow.
In Europe and America, orange is commonly associated with amusement, the unconventional, extroverts, fire, activity, danger, taste and aroma, the autumn season, and Protestantism. In Asia, it is an important symbolic colour of Buddhism and Hinduism.
This is a list of sources of light, including both natural and artificial sources, and both processes and devices.
A typical "light source" emits electromagnetic radiation in the visible spectrum. The list is oriented towards visible light: nearly everything emits photons through blackbody radiation. See also List of reflected light sources
In meteorology, a corona is produced by the diffraction of light from either the Sun or the Moon by individual small water droplets (and sometimes tiny ice crystals) of a cloud or on a foggy glass surface.
The corona consists of small number of concentric colored rings around the celestial object and a central bright aureole. The angular size of the corona depends on the diameters of the cloud droplets - small droplets produce large coronae. For the same reason, the corona is clearest when the size of the droplets is most uniform. Coronae differ from haloes in that the latter are formed by refraction (rather than diffraction) from comparatively large rather than small ice crystals. Reddish colors always occupy the outer part of a corona's ring. (This is an atmospheric Airy disc.)