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للاشتراك في (قناة العلم والإيمان): واتساب - يوتيوب

شاهد أكثر
شاهد أقل

The Solar System

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  • The Solar System

    THE SUN



    The Sun (Latin: Sol), a yellow dwarf, 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 98.6% of the Solar System's mass. The mean distance of the Sun from the Earth is approximately 149,600,000 kilometers, or 92,960,000 miles, and its light travels this distance in 8.3 minutes. 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 surface of 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 (5,500 C) giving it a white color that often, because of atmospheric scattering, appears yellow when seen from the surface of the Earth. This is a subtractive effect, as the preferential scattering of shorter wavelength light removes enough violet and blue light, leaving a range of frequencies that is perceived by the human eye as yellow. It is this scattering of light at the blue end of the spectrum that gives the surrounding sky its color. When the Sun is low in the sky, even more light is scattered so that the Sun appears orange or even red

    The Sun's spectrum contains lines of ionized and neutral ************ls 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 orbits the center of the Milky Way galaxy at a distance of approximately 24,000 to 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
    . This is equivalent to about one light-year every 1,190 years, and about one AU every 7 days. These measurements of galactic distance and speed are as accurate as we can get given our current knowledge, but may change as we learn more. 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.
    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 absolute magnitude as a fourth magnitude star (M=4.83).

    Will Be Continued




  • #2
    Oh Masha-Allah. It's my honour to read your first English post and to be the first member who comments on it


    Dear brother Taer Al Mas`a , many thanks for sharing such a piece with us.You must be interested in such subjects as I can see that from your signature

    May Allah (s.w.t ) Reward you & Protect you

    Waiting for the continuation

    Kind Regards Always

    تعليق


    • #3
      Thanks dear brother for this scientific sharing
      Waiting for the continuation

      تعليق


      • #4
        Thank you a lot

        I like this kind of topic

        تعليق


        • #5
          المشاركة الأصلية بواسطة Fattema
          Oh Masha-Allah. It's my honour to read your first English post and to be the first member who comments on it


          Dear brother Taer Al Mas`a , many thanks for sharing such a piece with us.You must be interested in such subjects as I can see that from your signature

          May Allah (s.w.t ) Reward you & Protect you

          Waiting for the continuation

          Kind Regards Always

          Assalam Alaykum

          Welcome dear sister Fattema

          Definitely, seeing first reply on my first English topic coming from our dear sister Fattema is my great honor and pleasure, too

          And of course you are most welcome my dear sister

          Yes, you're right , I'm very interested in learning everything about astronomy, it is my favorite subject

          I'm happy to see your nice comment and that's really will encourage me for giving more

          I hope you will enjoy this journey Insha-Allah

          Thanks a lot
          Respects & Regards

          تعليق


          • #6
            المشاركة الأصلية بواسطة المستفيد
            Thanks dear brother for this scientific sharing
            Waiting for the continuation

            Assalam Alaykum

            Many thanks to you our dear moderator

            May Allah bless you

            تعليق


            • #7
              المشاركة الأصلية بواسطة نور عيني فاطمة
              Thank you a lot

              I like this kind of topic
              Thanks a lot to you too our dear sister
              نور عيني فاطمة
              May Allah bless you

              تعليق


              • #8

                I will continue posting soon Insha Allah



                تعليق


                • #9
                  Masha-Allah Mr. Astronomer

                  We're still waiting

                  Good Luck

                  تعليق


                  • #10
                    المشاركة الأصلية بواسطة Fattema
                    Masha-Allah Mr. Astronomer

                    We're still waiting

                    Good Luck

                    Ms.Astronomer

                    Insha Allah I will be amateur Astronomer, just need your Duas

                    تعليق


                    • #11
                      المشاركة الأصلية بواسطة طائر المساء
                      Ms.Astronomer


                      Insha Allah I will be amateur Astronomer, just need your Duas




                      Me ! Ms. Astronomer ! No No No ! Allah La Egooleh !

                      I left all the astronomical BZNZ for you !

                      Insha-Allah you're always in our Duas

                      May your troubles be less,
                      May your blessings be more,
                      May nothing but happiness come through your door!


                      تعليق


                      • #12
                        المشاركة الأصلية بواسطة Fattema
                        [/center]


                        Me ! Ms. Astronomer ! No No No ! Allah La Egooleh !

                        I left all the astronomical BZNZ for you !

                        Insha-Allah you're always in our Duas

                        May your troubles be less,
                        May your blessings be more,
                        May nothing but happiness come through your door!

                        Why No! It is so fantastic field

                        Perhaps you will like it after finishing this topic who knows?

                        I'm very thankful dear sister for your Duas,may Allah bless you and keep you

                        With my kind respect & regards



                        تعليق


                        • #13



                          Structure of The Sun

                          The Sun is a yellow main sequence star comprising about 99% of the total mass of the Solar System. It is a near-perfect sphere, with an oblateness estimated at about 9 millionths which means that its polar diameter differs from its equatorial diameter by only 10 km (6 mi). As the Sun exists in a plasmatic state and is not solid, it rotates faster at its equator than at its poles. This behavior is known as differential rotation. The period of this actual rotation is approximately 25 days at the equator and 35 days at the poles. However, due to our constantly changing vantage point from the Earth as it orbits the Sun, the apparent rotation of the star at its equator is about 28 days. The centrifugal effect of this slow rotation is 18 million times weaker than the surface gravity at the Sun's equator. The tidal effect of the planets is even weaker, and does not significantly affect the shape of the Sun.

                          The Sun does not have a definite boundary as rocky planets do, and in its outer parts the density of its gases drops approximately exponentially with increasing distance from its center. Nevertheless, it has a well-defined interior structure, described below. The Sun's radius is measured from its center to the edge of the photosphere. This is simply the layer above which the gases are too cool or too thin to radiate a significant amount of light, and is therefore the surface most readily visible to the naked eye. The solar core comprises 10 percent of its total volume, but 40 percent of its total mass.

                          The solar interior is not directly observable, and the Sun itself is opaque to electromagnetic radiation. However, just as seismology uses waves generated by earthquakes to reveal the interior structure of the Earth, the discipline of helioseismology makes use of pressure waves (infrasound) traversing the Sun's interior to measure and visualize the star's inner structure. Computer modeling of the Sun is also used as a theoretical tool to investigate its deeper layers.



                          Core



                          The core of the Sun is considered to extend from the center to about 0.2 solar radii. It has a density of up to 150,000 kg/m3 (150 times the density of water on Earth) and a temperature of close to 13,600,000 kelvins (by contrast, the surface of the Sun is around 5,800 kelvins). Recent analysis of SOHO mission data favors a faster rotation rate in the core than in the rest of the radiative zone. Through most of the Sun's life, energy is produced by nuclear fusion through a series of steps called the p–p (proton–proton) chain; this process converts hydrogen into helium. The core is the only in the Sun that produces an appreciable amount of heat via fusion: the rest of the star is heated by energy that is transferred outward from the core. All of the energy produced by fusion in the core must travel through many successive layers to the solar photosphere before it escapes into space as sunlight or kinetic energy of particles.

                          About 3.4×1038 protons (hydrogen nuclei) are converted into helium nuclei every second (out of ~8.9×1056 total amount of free protons in the Sun), releasing energy at the matter–energy conversion rate of 4.26 million metric tons per second, 383 yottawatts (3.83×1026 W) or 9.15×1010 megatons of TNT per second. This actually corresponds to a surprisingly low rate of energy production in the Sun's core—about 0.3 W/m3 (watts per cubic meter). This is less power than generated by a candle. Power density is about 6 µW/kg of matter. For comparison, the human body produces heat at approximately the rate 1.2 W/kg, roughly a million times greater per unit mass. The use of plasma with similar parameters for energy production on Earth would be completely impractical—even a modest 1 GW fusion power plant would require about 170 billion metric ton of plasma occupying almost one cubic mile. Hence, terrestrial fusion reactors utilize far higher plasma temperatures than those in Sun's interior.

                          The rate of nuclear fusion depends strongly on density and temperature, so the fusion rate in the core is in a self-correcting equilibrium: a slightly higher rate of fusion would cause the core to heat up more and expand slightly against the weight of the outer layers, reducing the fusion rate and correcting the perturbation; and a slightly lower rate would cause the core to cool and shrink slightly, increasing the fusion rate and again reverting it to its present level.

                          The high-energy photons (gamma rays) released in fusion reactions are absorbed in only a few millimeters of solar plasma and then re-emitted again in random direction (and at slightly lower energy)—so it takes a long time for radiation to reach the Sun's surface. Estimates of the "photon travel time" range between 10,000 and 170,000 years.

                          After a final trip through the convective outer layer to the transparent "surface" of the photosphere, the photons escape as visible light. Each gamma ray in the Sun's core is converted into several million visible light photons before escaping into space. Neutrinos are also released by the fusion reactions in the core, but unlike photons they rarely interact with matter, so almost all are able to escape the Sun immediately. For many years measurements of the number of neutrinos produced in the Sun were lower than theories predicted by a factor of 3. This discrepancy was recently resolved through the discovery of the effects of neutrino oscillation: the Sun in fact emits the number of neutrinos predicted by the theory, but neutrino detectors were missing 2/3 of them because the neutrinos had changed flavor.


                          Radiative zone

                          From about 0.2 to about 0.7 solar radii, solar material is hot and dense enough that thermal radiation is sufficient to transfer the intense heat of the core outward. In this zone there is no thermal convection; while the material grows cooler as altitude increases, this temperature gradient is less than the value of adiabatic lapse rate and hence cannot drive convection. Heat is transferred by radiation—ions of hydrogen and helium emit photons, which travel a brief distance before being reabsorbed by other ions. In this way energy makes its way very slowly (see above) outward.
                          Between the radiative zone and the convection zone is a transition layer called the tachocline. This is a region where the sharp regime change between the uniform rotation of the radiative zone and the differential rotation of the convection zone results in a large shear—a condition where successive vertical layers slide past one another.


                          Convection zone

                          In the Sun's outer layer (down to approximately 70% of the solar radius), the solar plasma is not dense enough or hot enough to transfer the heat energy of the interior outward via radiation. As a result, thermal convection occurs as thermal columns carry hot material to the surface (photosphere) of the Sun. Once the material cools off at the surface, it plunges back downward to the base of the convection zone, to receive more heat from the top of the radiative zone. Convective overshoot is thought to occur at the base of the convection zone, carrying turbulent downflows into the outer layers of the radiative zone.
                          The thermal columns in the convection zone form an imprint on the surface of the Sun, in the form of the solar granulation and supergranulation. The turbulent convection of this outer part of the solar interior gives rise to a "small-scale" dynamo that produces magnetic north and south poles all over the surface of the Sun.
                          The Sun's thermal columns are Bénard cells and therefore tend to be hexagonal prisms.


                          Photosphere

                          The visible surface of the Sun, the photosphere, is the layer below which the Sun becomes opaque to visible light. Above the photosphere visible sunlight is free to propagate into space, and its energy escapes the Sun entirely. The change in opacity is due to the decreasing amount of H- ions, which absorb visible light easily. Conversely, the visible light we see is produced as electrons react with hydrogen atoms to produce H- ions. The photosphere is actually tens to hundreds of kilometers thick, being slightly less opaque than air on Earth. Because the upper part of the photosphere is cooler than the lower part, an image of the Sun appears brighter in the center than on the edge or limb of the solar disk, in a phenomenon known as limb darkening. Sunlight has approximately a black-body spectrum that indicates its temperature is about 6,000 K, interspersed with atomic absorption lines from the tenuous layers above the photosphere. The photosphere has a particle density of about 1023 m−3 (this is about 1% of the particle density of Earth's atmosphere at sea level).

                          During early studies of the optical spectrum of the photosphere, some absorption lines were found that did not correspond to any chemical elements then known on Earth. In 1868, Norman Lockyer hypothesized that these absorption lines were because of a new element which he dubbed "helium", after the Greek Sun god Helios. It was not until 25 years later that helium was isolated on Earth.


                          Atmosphere

                          The parts of the Sun above the photosphere are referred to collectively as the solar atmosphere. They can be viewed with telescopes operating across the electromagnetic spectrum, from radio through visible light to gamma rays, and comprise five principal zones: the temperature minimum, the chromosphere, the transition region, the corona, and the heliosphere. The heliosphere, which may be considered the tenuous outer atmosphere of the Sun, extends outward past the orbit of Pluto to the heliopause, where it forms a sharp shock front boundary with the interstellar medium. The chromosphere, transition region, and corona are much hotter than the surface of the Sun. The reason why has not been conclusively proven; evidence suggests that Alfvén waves may have enough energy to heat the corona.

                          The coolest layer of the Sun is a temperature minimum region about 500 km above the photosphere, with a temperature of about 4,000 K. This part of the Sun is cool enough to support simple molecules such as carbon monoxide and water, which can be detected by their absorption spectra.

                          Above the temperature minimum layer is a thin layer about 2,500 km thick, dominated by a spectrum of emission and absorption lines. It is called the chromosphere from the Greek root chroma, meaning color, because the chromosphere is visible as a colored flash at the beginning and end of total eclipses of the Sun. The temperature in the chromosphere increases gradually with altitude, ranging up to around 100,000 K near the top.






                          Above the chromosphere is a transition region in which the temperature rises rapidly from around 100,000 K to coronal temperatures closer to one million K. The increase is because of a phase transition as helium within the region becomes fully ionized by the high temperatures. The transition region does not occur at a well-defined altitude. Rather, it forms a kind of nimbus around chromospheric features such as spicules and filaments, and is in constant, chaotic motion. The transition region is not easily visible from Earth's surface, but is readily observable from space by instruments sensitive to the far ultraviolet portion of the spectrum.
                          The corona is the extended outer atmosphere of the Sun, which is much larger in volume than the Sun itself. The corona merges smoothly with the solar wind that fills the Solar System and heliosphere. The low corona, which is very near the surface of the Sun, has a particle density of 1014–1016 m−3. (Earth's atmosphere near sea level has a particle density of about 2×1025 m−3.) The temperature of the corona is several million kelvins. While no complete theory yet exists to account for the temperature of the corona, at least some of its heat is known to be from magnetic reconnection.
                          The heliosphere extends from approximately 20 solar radii (0.1 AU) to the outer fringes of the Solar System. Its inner boundary is defined as the layer in which the flow of the solar wind becomes superalfvénic—that is, where the flow becomes faster than the speed of Alfvén waves.[citation needed] Turbulence and dynamic forces outside this boundary cannot affect the shape of the solar corona within, because the information can only travel at the speed of Alfvén waves. The solar wind travels outward continuously through the heliosphere, forming the solar magnetic field into a spiral shape, until it impacts the heliopause more than 50 AU from the Sun. In December 2004, the Voyager 1 probe passed through a shock front that is thought to be part of the heliopause. Both of the Voyager probes have recorded higher levels of energetic particles as they approach the boundary

                          Will be continued






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                          • #14
                            Masha-Allah ! What a research !

                            Well-done job Mr Astronomer

                            Interesting but I still don't wanna be Ms Astronomer

                            Keep going and waiting for the next part

                            Take care



                            تعليق


                            • #15
                              المشاركة الأصلية بواسطة Fattema
                              Masha-Allah ! What a research !

                              Well-done job Mr Astronomer

                              Interesting but I still don't wanna be Ms Astronomer

                              Keep going and waiting for the next part

                              Take care


                              I know it is very short

                              At this stage it is interesting for you and that's good

                              After posting next part you will wanna to be Ms Astronomer

                              Believe me

                              Take care

                              Respects & regards

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