≈ 220km/s (orbit around the center of the Milky Way) ≈ 20km/s (relative to average velocity of other stars in stellar neighborhood) ≈ 370km/s[6] (relative to thecosmic microwave background)
TheSun, also known asSol, is astar at the center of thesolar system. It is a white star that gives off different types ofenergy such asinfrared energy (heat),ultraviolet light,radio waves and light. It gives off thelight and heat that makelife onEarth possible. Without it, Earth would be a frozen, lifeless place. It is a huge ball of hot gases, mostlyhydrogen andhelium.
The Sun is nearly a perfectsphere and has adiameter of about 1.39 million kilometers (or 864,000 miles), which is about 109 times wider than Earth. Its mass is 333,000 times heavier than Earth, and it makes up over 99.8% of all the mass in theSolar System. That is why itsgravity controls the movement of all theplanets,moons,asteroids, andcomets. The Sun’s energy comes fromnuclear reactions deep inside it, wherehydrogen is turned intohelium. This process releases a lot ofenergy, which travels aslight andheat across space to reach Earth. It takes about 8 minutes forsunlight to travel the 150 million kilometers (93 million miles) from the Sun to Earth. This distance is called 1Astronomical Unit (AU). The Sun is also part of theMilky Way galaxy, slowly orbiting around thegalaxy’s center at a distance of about 24,000 to 28,000 light-years. Its outer layer, called thephotosphere, is mostlyhydrogen (~73%) andhelium (~25%), but also contains tiny amounts of other elements likeoxygen,carbon,neon, andiron.
The Sun is a type ofstar called aG-type main-sequence star, sometimes nicknamed a yellow dwarf, even though its light is actuallywhite, not yellow. It looks yellow because of theatmosphere.Sunlight is made up of all the colors,red,orange,yellow,green,blue,indigo, andviolet. When sunlight passes through Earth’s atmosphere, the shorterwavelengths, like blue and violet, get scattered in all directions. That is also why thesky looks blue. The longer wavelengths, like yellow and red, do not scatter as much, so they reach our eyes more directly. That is why the Sun looks yellow when it is seen from the ground. But if the Sun is seen from space, where there is no atmosphere, it would look white, which is its realcolor.
The Sun was born about 4.6 billion years ago. It formed when a huge cloud ofgas anddust in space began to collapse under its own gravity. Most of the material got pulled into the center, which became the Sun. The leftover material flattened into aspinning disk and formed the planets, moons, asteroids, and comets, creating the Solar System. As the Sun's core got hot and dense, it started a process callednuclear fusion. This is when hydrogen atoms combine to make helium, releasing an enormous amount of energy. Every second, the Sun turns about 600 billion kilograms of hydrogen into helium and converts 4 billion kilograms of matter intoenergy. This energy is what gives ussunlight andheat, keeping our planet warm and life-friendly.
The Sun is about 4.5billion years old. The Sun is about a hundred times as wide as the Earth. It has a mass of1.9891×1030kg. This is 333,000 times the mass of the Earth. 1.3 million Earths can fit inside the Sun.[16] The Sun fuses about 600 million tons ofhydrogen intohelium every second.
The Sun is the main source of energy for the Earth. This energy is made deep inside the Sun in a process callednuclear fusion. Four hydrogen atoms are fused together to make onehelium atom. Some of the leftover matter turns into energy. This is the same way energy is released in a hydrogen bomb.[source?]
It can take between 10,000 and 170,000 years for theenergy in the core of the Sun to escape. The Sun is the most important source ofenergy forlife onEarth. Without the Sun, there would be novegetation onEarth: everyplant needs light to live and grow. Everything on Earth would freeze over without the Sun. The Sun gives the Earth heat as well as light. Plants make oxygen byphotosynthesis. Allhumans andanimals breathe oxygen. TheEarth's position in the Solar System is just right for the development of life on Earth.[source?]
The Sun is the brightest object in the Earth's sky. It has anapparent magnitude of −26.74.[20] It takes 8 minutes and 20 seconds forlight to travel from the Sun's surface to Earth's surface.[21]
Scientists think that the Sun started from a very large cloud of dust and small bits of ice about 4.567billion years ago.[22]
At the center of that huge cloud,gravity caused the material to build up into a ball. Once this got big enough, the huge pressure inside started afusion reaction. The energy this released caused that ball to heat and shine.
The Sun and everything that orbits it is in theMilky Way galaxy. The Sun orbits around thecentre of the Milky Way. It takes along everything in the Solar System. The Sun moves at 820,000km an hour. At that speed, it still takes 230 million years for a full orbit. Since the Sun is all gas, surface features come and go. If the Sun is viewed through a specialsolar telescope, dark areas calledsunspots can be seen. These areas are caused by the Sun'smagnetic field. The sunspots only look dark because the rest of the Sun is very bright.[source?]
Somespace telescopes, including the ones that orbit the Sun have seen hugearches of the Sun's matter extend suddenly from the Sun. These are called solar prominences. Solar prominences come in many different shapes and sizes. Some of them are so large that the Earth could fit inside of them, and a few are shaped like hands.Solar flares also come and go. Sunspots, prominences and flares become rare, and then numerous, and then rare again, every 11 years.[source?]
This is the surface of the Sun. The light that the Earth receives from the Sun isradiated from this layer. Below this layer, the Sun isopaque, or nottransparent to light.[source?]
The Sun is mainly composed of hydrogen and helium. All elements heavier than hydrogen and helium, account for less than 2% of the mass of the Sun.[23][24] The Sun's chemical composition was got from theinterstellar medium. The hydrogen and most of the helium in the Sun would have been produced byBig Bang nucleosynthesis in the first 20 minutes of theuniverse. The heavier elements were produced by stars that died before the Sun was formed. The heavier elements were released into the interstellar medium when stars exploded assupernova.[23][24]
Five layers make up theatmosphere of the Sun. Thechromosphere, transition region, andcorona are much hotter than the outer photosphere surface of the Sun.[25] It is believed thatAlfvén waves may pass through to heat the corona.[26]
Theminimum temperature zone, the coolest layer of the Sun, is about500 kilometres (310 miles) above the photosphere. It has a temperature of about4,100K (3,830°C; 6,920°F).[25] This part of the Sun is cool enough to allow simple molecules such ascarbon monoxide and water to form. These molecules can be seen on the Sun with special instruments calledspectroscopes.[27]
Thechromosphere is the first layer of the Sun which can be seen, especially during asolar eclipse when the moon is covering most of the Sun and blocking the brightest light.
Thesolar transition region is the part of the Sun's atmosphere, between the chromosphere and outer part called thecorona.[28] It can be seen fromspace using telescopes that can senseultraviolet light. The transition is between two very different layers. In the bottom part it touches the photosphere and gravity shapes the features. At the top, the transition layer touches the corona.
Thecorona is the outer atmosphere of the Sun and is much bigger than the rest of the Sun. The corona continuously expands into space forming thesolar wind, which fills all the Solar System.[29] The average temperature of the corona and solar wind is about1,000,000–2,000,000K (1,800,000–3,600,000°F). In the hottest regions it is8,000,000–20,000,000K (14,400,000–36,000,000°F).[30] We do not understand why the corona is so hot.[29][30] It can be seen during asolar eclipse or with an instrument called acoronagraph.
A solareclipse appears when the moon is between the Earth and Sun. The last total solar eclipse occurred on December 26, 2019, and was visible fromSaudi Arabia,India,Sumatra andBorneo, with a partial eclipse visible inAustralia and much of Asia.
Alunar eclipse happens when the moon passes through the shadow of the Earth which can only occur during a full moon. The number of lunar eclipses in a single year can range from 0 to 3. Partial eclipses slightly outnumber total eclipses by 7 to 6.[32]
Astrophysicists say our Sun is aG-type main-sequence star in the middle of itslife. In about billion years, increased solar energy will boil away theEarth's atmosphere and oceans. In a few more billion years, they think the Sun will get bigger and become ared giant star. The Sun would be up to 250 times its current size, as big as1.4AU (210,000,000 kilometres; 130,000,000 miles) and swallow up the Earth.
Earth's fate is still unknown. In the long term, the Earth's future depends on the Sun, and the Sun is going to be fairly stable for the next 5billion years.[33][34] Calculations suggest that the Earth might move to a wider orbit. This is because about 30% of the Sun's mass will blow away in thesolar wind.
However, in the very long term the Earth will probably be destroyed as the Sun increases in size. Stars like the Sun becomered giants at a later stage.[35] The Sun will expand beyond the orbits ofMercury,Venus, and probably Earth. In any event, the ocean and air would have vanished before the Sun gets to that stage.
After the Sun reaches a point where it can no longer get bigger, it will lose its layers and form aplanetary nebula. Eventually, the Sun will shrink into awhite dwarf. Then, over several hundred billion or even a trillion years, the Sun would fade into ablack dwarf.
↑Mamajek, E.E.; Prsa, A.; Torres, G.; et, al. (2015), "IAU 2015 Resolution B3 on Recommended Nominal Conversion Constants for Selected Solar and Planetary Properties",arXiv:1510.07674 [astro-ph.SR]
12Hansen, Carl J. (2004).Stellar interiors: physical principles, structure, and evolution. Kawaler, Steven D., Trimble, Virginia. (2nded.). New York: Springer.ISBN0-387-20089-4.OCLC53083938.
12Russell, C.T. (2001). "Solar wind and interplanetary magnetic filed: A tutorial". In Song, Paul; Singer, Howard J. and Siscoe, George L. (ed.).Space weather (Geophysical Monograph)(PDF). American Geophysical Union. pp.73–88.ISBN978-0-87590-984-4. Archived fromthe original(PDF) on 2018-10-01. Retrieved2012-12-12.{{cite book}}: CS1 maint: multiple names: editors list (link)
12Erdèlyi R. & Ballai I. 2007. Heating of the solar and stellar coronae: a review.Astron. Nachr.328 (8): 726–733
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