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Another component of the solar system is the solar wind. The Sun contains more than 99% of the mass of the solar system; most of the rest is distributed among the planets, with Jupiter containing about 70%. According to the prevailing theory, the solar system originated from the solar nebula. See also asteroid; Centaur object; Ceres; comet; Earth; Eris; Jupiter; Kuiper belt; Mars; Mercury; meteorite; Neptune; Oort cloud; Pluto; Saturn; Uranus; Venus.
Solar nebula
Gaseous cloud from which, in the nebular hypothesis of the origin of the solar system, the Sun and planets formed by condensation.
In 1755 Immanuel Kant suggested that a nebula gradually pulled together by its own gravity developed into the Sun and planets. Pierre-Simon, marquis de Laplace, in 1796 proposed a similar model, in which a rotating and contracting cloud of gas—the young Sun—shed concentric rings of matter that condensed into the planets. But James Clerk Maxwell showed that, if all the matter in the known planets had once been distributed this way, shearing forces would have prevented such condensation. Another objection was that the Sun has less angular momentum than the theory seems to require. In the early 20th century most astronomers preferred the collision theory: that the planets formed as a result of a close approach to the Sun by another star. Eventually, however, stronger objections were mounted to the collision theory than to the nebular hypothesis, and a modified version of the latter—in which a rotating disk of matter gave rise to the planets through successively larger agglomerations, from dust grains through planetesimals and protoplanets—became the prevailing theory of the solar system's origin.
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Use of solar radiation to heat water or air in buildings.
There are two types: passive and active. Passive heating relies on architectural design; the building's siting, orientation, layout, materials, and construction are utilized to maximize the heating effect of sunlight falling on it. A well-insulated building with a large south-facing window, for instance, can trap heat on sunny days and reduce reliance on gas, oil, or electricity. Brick, stone, or tile capacity walls are often incorporated to absorb the sun's energy and radiate it into the interior, usually after a time lag of several hours. In active solar heating, mechanical means are used to collect, store, and distribute solar energy. In liquid-based systems, a blackened metal plate on the exterior absorbs sunlight and traps heat, which is transferred to a carrier fluid. Alternatively, fluid may be pumped through a glass tube or volume of space onto which sunlight has been focused by mirrors. After picking up heat from the collector, the warm fluid is pumped to an insulated storage tank. The system can supply a home with hot water from the tank or provide space heating with the warmed water flowing through tubes in floors and ceilings
Copernican System
Model of the solar system centred on the Sun, with Earth and other planets revolving around it, formulated by Nicolaus Copernicus in the mid 16th century.
Having the Sun in this central position explained the apparent motion of planets relative to the fixed stars and was truer than the Earth-centred Ptolemaic system (see Ptolemy). Scientifically, the Copernican system led to belief in a much larger universe than before (because, if the Earth revolved around the Sun, the stars would have to be very distant not to appear to alter their position); more broadly, the Copernican principle is invoked to argue against any theory that would give the solar system a special place in the universe. Dethronement of Earth from the centre of the universe caused profound shock: the Copernican system challenged the entire system of ancient authority and required a complete change in the philosophical conception of the universe.
Solar plasma
Electrically conducting medium in which there are roughly equal numbers of positively and negatively charged particles, produced when the atoms in a gas become ionized (see ionization).
Plasma is sometimes called the fourth state of matter (the first three being solid, liquid, and gas). A plasma is unique in the way it interacts with itself, with electric and magnetic fields, and with its environment. It can be thought of as a collection of ions, electrons, neutral atoms and molecules, and photons in which some atoms are being ionized at the same time as electrons are recombining with other ions to form neutral particles, while photons are continuously being produced and absorbed. It is estimated that more than 99% of the matter in the universe exists in the plasma state.
Corona
Outermost region of the Sun's (or any star's) atmosphere, consisting of plasma.
Photograph:Total solar eclipse. The delicately structured glow of the solar corona—or solar …
* Total solar eclipse. The delicately structured glow of the solar corona—or solar …
The Sun's corona has a temperature of about 3.6 million °F (2 million °C) and a very low density. Extending more than 8 million mi (13 million km) from the photosphere, it has no definite boundaries, continually varying in size and shape as it is affected by the Sun's magnetic field. The solar wind is formed by expansion of coronal gases. Only about half as bright as the full moon, the corona is overwhelmed by the brilliance of the solar surface and normally not visible to the unaided eye, but a total eclipse permits naked-eye observations.
Solar WindFlux of particles, chiefly protons, electrons, and helium nuclei accelerated by the hot solar corona's high temperatures to speeds high enough to allow them to escape the Sun.
Solar flares increase its intensity. The solar wind deflects planets' magnetospheres and the ion tails of comets away from the Sun. The uninterrupted portion of the solar wind continues to travel to a distance of about 20 astronomical units, where it cools and eventually diffuses into interstellar space. See also heliopause.
Source:Britannica Encyclpedia
