Documentary About The Sun, Earth and Universe. The Sun is the star at the center of the Solar System. It has a diameter of about 1,392,000 kilometers (865,000 mi), 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. About three quarters of the Sun's mass consists of hydrogen, while the rest is mostly helium. Less than 2% consists of heavier elements, including iron, oxygen, carbon, neon, and others.
The Sun's color is white, although from the surface of the Earth it may appear yellow because of atmospheric scattering.Its stellar classification, based on spectral class, is G2V, and is informally designated a yellow star, because the majority of its radiation is in the yellow-green portion of the visible spectrum.In this spectral class label, G2 indicates its surface temperature of approximately 5,778 K (5,505 °C; 9,941 °F), and V (Roman five) 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 430--600 million tons of hydrogen each second.The Sun is currently traveling through the Local Interstellar Cloud in the Local Bubble zone, within the inner rim of the Orion Arm of the Milky Way galaxy. Of the 50 nearest stellar systems within 17 light-years from Earth, the Sun ranks 4th in mass.The Sun orbits the center of the Milky Way at a distance of approximately 24,000--26,000 light years from the galactic center, completing one clockwise orbit, as viewed from the galactic north pole, in about 225--250 million years.The mean distance of the Sun from the Earth is approximately 149.6 million kilometers (1 AU), though this varies as the Earth moves from perihelion in January to aphelion in July.At this average distance, light travels from the Sun to Earth in about 8 minutes and 19 seconds.The Sun is a G-type main sequence star comprising about 99.86% of the total mass of the Solar System.
A recent theory claims that there are magnetic instabilities in the core of the Sun that cause fluctuations with periods of either 41,000 or 100,000 years. These could provide a better explanation of the ice ages than the Milankovitch cycles.The Sun was formed about 4.57 billion years ago when a hydrogen molecular cloud collapsed.Solar formation is dated in two ways: the Sun's current main sequence age, determined using computer models of stellar evolution and nucleocosmochronology, is thought to be about 4.57 billion years.This is in close accord with the radiometric date of the oldest Solar System material, at 4.567 billion years ago.The Sun is about halfway through its main-sequence evolution, during which nuclear fusion reactions in its core fuse hydrogen into helium. Each second, more than four million metric tons of matter are converted into energy within the Sun's core, producing neutrinos and solar radiation. At this rate, the Sun has so far converted around 100 Earth-masses of matter into energy. The Sun will spend a total of approximately 10 billion years as a main sequence star.