Sun
hideThe Sun is the star at the center of the Solar System. The Earth and other matter (including other planets, asteroids, meteoroids, comets, and dust) orbit the Sun, which by itself accounts for about 99.86% of the Solar System's mass. The mean distance of the Sun from the Earth is approximately 149.6 million kilometers (93.0 million miles), and its light travels this distance in 8 minutes and 19 seconds. This distance varies throughout the year from a minimum of 147.1 million kilometers (91.4 million miles) on the perihelion (around 3 January), to a maximum of 152.1 million kilometers (94.5 million miles) on the aphelion (around 4 July). Energy from the Sun, in the form of sunlight, supports almost all life on Earth via photosynthesis, and drives the Earth's climate and weather. The Sun consists of hydrogen (about 74% of its mass, or 92% of its volume), helium (about 24% of mass, 7% of volume), and trace quantities of other elements, including iron, nickel, oxygen, silicon, sulfur, magnesium, carbon, neon, calcium, and chromium.
The Sun has a spectral class of G2V. G2 means that it has a surface temperature of approximately 5,780 K (5,510 °C) giving it a white color, which often appears as yellow when seen from the surface of the Earth because of atmospheric scattering. It is this scattering of light at the blue end of the spectrum that gives the surrounding sky its color. The Sun's spectrum contains lines of ionized and neutral metals as well as very weak hydrogen lines. The V (Roman five) in the spectral class indicates that the Sun, like most stars, is a main sequence star. This means that it generates its energy by nuclear fusion of hydrogen nuclei into helium. There are more than 100 million G2 class stars in our galaxy. Once regarded as a small and relatively insignificant star, the Sun is now known to be brighter than 85% of the stars in the galaxy, most of which are red dwarfs.
The Sun's hot corona continuously expands in space creating the solar wind, a hypersonic stream of charged particles that extends to the heliopause at roughly 100 AU. The bubble in the interstellar medium formed by the solar wind, the heliosphere, is the largest continuous structure in the Solar System.
The Sun is currently traveling through the Local Interstellar Cloud in the low-density Local Bubble zone of diffuse high-temperature gas, in the inner rim of the Orion Arm of the Milky Way Galaxy, between the larger Perseus and Sagittarius arms of the galaxy. Of the 50 nearest stellar systems within 17 light-years (1.6×1014 km) from the Earth, the Sun ranks 4th in mass as a fourth magnitude star (M = +4.83)., although slightly different values for the magnitude have been published, for example 4.85 and 4.81. The Sun orbits the center of the Milky Way galaxy at a distance of approximately 24,000–26,000 light years from the galactic center, moving generally in the direction of Cygnus and completing one revolution in about 225–250 million years (one Galactic year). Its orbital speed was thought to be 220 ± 20, km/s but a new estimate gives 251 km/s. Since our galaxy is moving with respect to the cosmic microwave background radiation (CMB) in the direction of Hydra with a speed of 550 km/s, the sun's resultant velocity with respect to the CMB is about 370 km/s in the direction of Crater or Leo.
For more information about Sun, read the full article at
Wikipedia.
This text uses material from Wikipedia and is available under the GNU Free Documentation License.
News tagged with sun
Sun or shade: Pecan leaves' photosynthetic light response evaluated
Nov 03, 2009 |
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Pecan, the most valuable nut tree native to North America, is native from northern Illinois and southeastern Iowa to the Gulf Coast of the United States, where it grows abundantly along the Mississippi River, ...
Micro Sparky: Engineering the tiniest Sun Devil
Oct 30, 2009 |
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(PhysOrg.com) -- An Arizona State University engineering student may have found the tiniest - yet most cleverly inventive - way to show school spirit.
New Celestial Map Gives Directions for GPS
Space & Earth / Space Exploration
Oct 29, 2009 |
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(PhysOrg.com) -- Many of us have been rescued from unfamiliar territory by directions from a Global Positioning System (GPS) navigator. GPS satellites send signals to a receiver in your GPS navigator, which ...
Sun CEO's pay package cut by a third in '09
Oct 29, 2009 |
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(AP) -- The value of Sun Microsystems Inc. CEO Jonathan Schwartz's latest pay package dropped 37 percent from last year as the company lost more than $2 billion and was in such dire financial shape that it ...
The Sun's Sneaky Variability
Space & Earth / Space Exploration
Oct 28, 2009 |
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Every 11 years, the sun undergoes a furious upheaval. Dark sunspots burst forth from beneath the sun's surface. Explosions as powerful as a billion atomic bombs spark intense flares of high-energy radiation. ...
A long night falls over Saturn's rings
Space & Earth / Space Exploration
Oct 24, 2009 |
4.8 / 5 (6) |
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As Saturn's rings orbit the planet, a section is typically in the planet's shadow, experiencing a brief night lasting from 6 to 14 hours. However, once approximately every 15 years, night falls over the entire ...
Sun cutting up to 3,000 jobs as awaits Oracle deal
Oct 20, 2009 |
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(AP) -- Sun Microsystems Inc. plans to eliminate up to 3,000 jobs, or 10 percent of its worldwide work force, as it awaits a takeover by Oracle Corp., a deal being held up by antitrust regulators in Europe.
Oracle's Larry Ellison to IBM: 'make our day'
Oct 15, 2009 |
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(AP) -- Larry Ellison ratcheted up his rhetoric against IBM Corp. on Wednesday, challenging Oracle Corp.'s longtime partner and rival to "make our day" in a battle over business software performance.
Some color shades offer better protection against sun’s ultraviolet rays
Oct 14, 2009 |
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Economy-minded consumers who want protection from the sun's harmful ultraviolet (UV) rays -- but rather not pay premium prices for sun-protective clothing -- should think blue and red, rather than yellow. ...
Oracle plays up promise of Sun take-over
Oct 12, 2009 |
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Oracle chief executive Larry Ellison opened fire on US technology veteran IBM and expressed optimism about the pending 7.4-billion-dollar-deal to buy Sun Microsystems.
US Solar Decathlon seeks best sun-powered homes
Oct 08, 2009 |
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For the past week on the National Mall in Washington, international crews have been busy putting up structures for an event showcasing a radiant source of energy that some once revered as a god.
Largest Ring Around Saturn Discovered
Oct 07, 2009 |
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(PhysOrg.com) -- NASA's Spitzer Space Telescope has discovered an enormous ring around Saturn -- by far the largest of the giant planet's many rings.
Amazon, Apple, Google, Yahoo! targeted in patent case
Oct 06, 2009 |
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A US technology company which won a patent case against software giant Microsoft filed suit on Tuesday against nearly two dozen other high-profile firms accusing them of violating the same patent.
Researchers identify better laser for treating facial spider veins
Oct 06, 2009 |
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(PhysOrg.com) -- Researchers from Boston University School of Medicine (BUSM) have concluded that the 940nm wavelength laser is superior for treating facial spider veins (telangiectasias) as compared to the 532nm wavelength ...
NRL Begins Southeast Asia Study of Aerosols Linked to Global Warming
Space & Earth / Earth Sciences
Sep 28, 2009 |
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(PhysOrg.com) -- NRL's Marine Meteorology Division has deployed the Mobile Atmosphere, Aerosol, and Radiation Characterization Observatory (MAARCO) to the National University of Singapore to begin the first ...
