The sun

The sun

• 1.
  THE SUN TheNearest Star to us
• 2.
  The Sun Thegovernor of Solar System. Only day time star and closest star to the Earth. It is 13,00,000 times bigger than Earth. The light takes 8.24 minutes to reach Earth. To cover its diameter, 109 Earth will be required. It emits the radiations in all Electromagnetic spectrum .
• 3.
  Physical Profile ofSun Observation data Mean distance from Earth 1.496×108 km Visual brightness (V) −26.74 Absolute magnitude 4.85 Spectral classification G2V Angular size 31.6′ – 32.7′ Physical characteristics Mean diameter 1.392×106 km Equatorial radius 6.955×105 km Mass 1.9891×1030 kg Average density 1.408×103 kg/m3 Equatorial surface gravity 274.0 m/s2 Escape velocity 617.7 km/s Temperature of surface (effective) 5,778 K Luminosity (Lsol) 3.846×1026 Orbital characteristics Mean distance from Milky Way core ~2.5×1017 km 26,000 light-years Galactic period (2.25–2.50) × 108 yrs Velocity ~220 km/s (orbit around the center of the Galaxy) Rotation characteristics Obliquity 7.25° (to the ecliptic) Sidereal Rotation period (at 16° latitude) 25.38 days (at equator) 25.05 days (at poles) 34.3 days Rotation velocity (at equator) 7.189×103 km/h
• 4.
  Atmosphere of Sun Sun’s atmosphere starts from and above the surface layer named ‘Photosphere’. The layer above Photosphere, with the thickness of ~2,000 KM is ‘Chromosphere’. The outermost layer of the Sun’s atmosphere is known as ‘Corona’, it extends upto millions of kilometer above Chromosphere. Chromosphere and Corona is visible only during Total Solar Eclipse.
• 5.
  Photosphere It isless than 500 KM deep. The photoshpere is the layer in the Sun’s atmosphere that is dense enough to emit plenty of light but not so dense that the light can’t escape. It is very-low-density gas. The density is 3400 times less dense than the air we breath. The layer below photosphere is dense and can produce continuous spectra, but atoms in the photosphere absorb photons of specific wavelengths producing absorption lines.
• 6.
  The layer hasa mottled appearance because it is made up of dark-edged regions. It is known as granules and pattern is called as granulation. Granule lasts for 10 to 20 minutes. Spectra shows that centers are a few hundred degrees hotter than the edges, and Doppler shifts reveals that the centers are rising and the edges are sinking at the speed of 1 km/sec.
• 7.
  Chromosphere Chromosphere is1000 times fainter than the photosphere. Characteristic flash seen during the total solar eclipse in pink colour is produced in chromosphere – it is a combination of emission lines in red, blue and violet Balmer line. Chromosphere has low-density gas. It is about 108 times less dense than the air we breath. At the bottom of layer temperature is low (4300 K) but then rises rapidly. The region where temperature rises rapidly is called transition region.
• 8.
  Corona Spectrum ofcorona showed that the temperature is in the order of million degree. It is not bright because it is very low density gas only 1-10 atoms/cm3. The study showed that the light from outer corona is reflected sunlight i.e. outer corona contains dust particles that reflects sunlight in all directions. Corona is the region where high speed winds are getting generated known as Solar Wind. It has the velocity of 300- 800 km/sec.
• 9.
  Internal Structure ofthe Sun
• 10.
  CORE of thesun It extends from 0 to 0.25 solar radii. It has the density of 150g/cm3. It has the temperature of 13.6 to 15 million K. It is the fastest rotating part. All of its energy generate in the core through nuclear fusion. 98% is through p-p chain and 2% is through CNO cycle.
• 11.
  Radiative Zone Thisis a region where the sharp regime change between the uniform rotation of the radiative zone and the differential rotation of the convection zone It starts from 0.25 to 0.70 solar radii. It is hot and dense which helps in transferring the matter from core to outer part through radiation. Material from bottom to top gets cooler with the altitude (7 million to 2 million K).
• 12.
  Magnetic Activities onthe Sun Solar Flare A solar flare is a violent explosion in the Sun's atmosphere with an energy equivalent to tens of millions of hydrogen bombs.
• 13.
  Sun Spot Sunspotis the easily observable magnetic activity on the Sun’s surface. Because of their cooler temperature region at the magnetic region it appears as a dark spot. The temperature of the sunspot is of the order of 4250K as compared to surrounding of 5700 K. It has a inside dark part known as umbra and outside lighter part known as penumbra. The presence of magnetic filed in the sunspot was first observed by Gorge Ellery Hale in 1908 through the Zeeman Effect.
• 14.
  How Aurora forms…
• 15.
  How big isthe Sun…
• 16.
  How small isthe Sun…
• 17.
  Life Cycle ofSun/Possible end of Sun