Related topics: nasa , earth
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
Keck Telescopes Take Deeper Look at Planetary Nurseries
Dec 23, 2009 |
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(PhysOrg.com) -- Astronomers using the W. M. Keck Observatory have peered far into a young planetary system, giving an unprecedented view of dust and gas that might eventually form planets similar to Jupiter, ...
Google-Fujitsu join 'smart objects' alliance
Dec 18, 2009 |
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Internet powerhouse Google and Japanese electronics giant Fujitsu have joined an alliance to promote the ability of objects from appliances to cars to communicate with one another online.
Twin study identifies factors associated with skin aging
Dec 21, 2009 |
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Smoking, being heavier, not using sunscreen and having had skin cancer appear to be associated with sun damage and aging of skin on the face, according to report based on a study of twins in the December issue of Archives of ...
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Critical protein helps mend damaged DNA
Dec 24, 2009 |
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In order to preserve our DNA, cells have developed an intricate system for monitoring and repairing DNA damage. Yet precisely how the initial damage signal is converted into a repair response remains unclear. Researchers ...
Sun and moon trigger deep tremors on San Andreas Fault
Space & Earth / Earth Sciences
Dec 23, 2009 |
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The faint tug of the sun and moon on the San Andreas Fault stimulates tremors deep underground, suggesting that the rock 15 miles below is lubricated with highly pressurized water that allows the rock to slip with little ...
Shallow Origins
Space & Earth / Earth Sciences
Dec 22, 2009 |
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In finding answers to the mystery of the origin of life, scientists may not have to dig too deep. New research is shedding light on shallower waters as a possible location for where life on Earth began.
Astronomers discover 'tilted planets'
Dec 22, 2009 |
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(PhysOrg.com) -- University of Exeter, UK, research has added to a growing evidence that several giant planets have orbits so tilted that their orbits can be perpendicular or even backwards relative to their ...
Kew botanists discover more than 250 new plant species in 250th anniversary year
Dec 22, 2009 |
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Giant rainforest trees, rare and beautiful orchids, spectacular palms, minute fungi, wild coffees and an ancient aquatic plant are among more than 250 new plant and fungi species discovered and described by botanists from ...
Study redefines placebo effect as part of effective treatment
Medicine & Health / Psychology & Psychiatry
Dec 22, 2009 |
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Researchers used the placebo effect to successfully treat psoriasis patients with one quarter to one half of their usual dose of a widely used steroid medication, according to an early study published online today in the ...
Heart transplant patients appear to have elevated risk for multiple skin cancers
Dec 21, 2009 |
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Many heart transplant patients develop multiple skin cancers, with increased risk for some skin cancers among patients with other cancers and with increasing age, according to a report in the December issue of Archives of ...
Brown dwarf pair mystifies astronomers
Dec 21, 2009 |
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(PhysOrg.com) -- Two brown dwarf-sized objects orbiting a giant old star show that planets may assemble around stars more quickly and efficiently than anyone thought possible, according to an international ...
A New Method of Estimating Stellar Distances
Dec 21, 2009 |
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(PhysOrg.com) -- The star Chi Cygni is located about 550 light-years away, in the direction of the constellation of Cygnus the Swan. It is a notable star because, unlike the sun which still burns hydrogen ...
Final launch of Ariane 5 GS completes busy year
Space & Earth / Space Exploration
Dec 21, 2009 |
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(PhysOrg.com) -- Last week, an Ariane 5 GS launcher lifted off from Europe’s Spaceport in French Guiana on a journey to place the French military reconnaissance satellite Helios-2B into Sun-synchronous polar ...
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