Solar System

Solar system definition

The sun along with eight planets , asteroids, and comets comprise the solar system. Such kinds of  planets which have greater densities known as inner or terrestrial planets . e.g . Mercury , Venus , Earth , and Mars and outer planets which have lower densities are Jupiter , Saturn , Uranus and Neptune.

The Sun 

  • The sun lie in the centre of the solar system.

  • The sun is made up of extremely hot gases mainly hydrogen..

  • The sun is 10^9  times bigger than the earth and weighs 2× 10^27 tonnes.



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solar system definition

  • The sun is approximately 150 million km away from the earth . The light from the sun reaches the earth in about 8 minutes.

  • The shining or glowing surface of the sun is called Photosphere . Above the Photosphere is red coloured Chromosphere . Beyond the Chromosphere is the Corona  visible during eclipses.

  • The temperature of the photosphere is about 6000℃  and that of the Chromosphere is about 32400 ℃ .The Sun's core is about 15 million degrees Celsius. But we don't feel that tremendous heat so much because it's far from us, despite being our closest star. 

  • It takes 250 million years to complete one revolution round its centre . This period is called Cosmic year.

  • Sun spots are dark patches notched on the surface of the Sun. They appear dark ,because they are cooler . They have a temperature of about 1500 ℃ .

  • The Aurora Borealis or northern lights are multicoloured lights that sweeps across the sky in waves and are visible in the arctic region .

  • The Aurora Australis or southern lights can be visible near the Antarctica region.
Beginning of the universe

Beginning of the Universe

The Big bang theory explains the origin of our universe . According to this theory , about 15 billion years ago , all cosmic matters were in a compressed state from which expansion started by a primordial explosion . This super dense ball broke to form galaxies, which again broke to form stars and finally stars broke to form planets including earth.
since the outer space is limitless, conventional units for measuring distances are not suitable . Hence new units as follows are used ;
  • Light year : Distance covered by light in one year in vaccum at a speed of 3× 10^8 m/s. 
  • 1 light year = 9.46 × 10^12 km

  • Astronomical unit ; The mean distance between the Sun and the Earth (1.49 ×10^8 km). one light year = 60,000 AU
  • Cosmic year: Sun's period of revolution around the galactc centre( 250 million years) . Also called as galactic year.

  • Parsec : Distance at which the mean radius of the Earth's orbit subtend an angle of one second of an arc . It is equal to 3.26 light years.

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Stars in the sky 

stars are self luminous bodies that account for 98 percent of the matter in the galaxy. In the universe some stars appear small but emit more energy than the other stars of the Milky way. Such stars are called Quasars. 

When the dense galactic nucleus compresses to form a star, this stage is called a protostar stage in star formation. Due to high temperature hydrogen converts to helium and heat and kight is emitted. Thus a star is formed.

 when the hydrogen of a star is depleted , its outer region swell and redden. The very, stage of the star is called a Red Giant. After 5 billion years, our Sun will turn into a Red Giant .

Novae Stars are stars whose brightness increases suddenly by 10 to 20 magnitudes due to explosions and then the stars again fade into normal brightness. Super Novae are stars whose brightness suddenly increases 20 times .

After the explosion the dense core of comparatively smaller stars is called White Dwarf. The dense core of comparatively larger stars is called the Neutron Star.

The Neutron stars rotate at a high speed emitting radio waves. Such stars are called Pulsars.

 The star's black hole stage happens when the old star collapses. Gravity in the hole becomes so intense that nothing, even light, escapes.


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The Universe facts

  • ALMA -  The Atacama Millimeter Array is an astronomical radio telescope interferometer in Northern Chile's Atacama Desert.

ALMA came in 1997, when the NRAO ( National Radio Astronomy Observatory) and the ESO ( European Southern Observatory) agreed to pursue a common project that merged the MMA and LSA.


  • The ALMA image shows that cosmic dust, which is the material component of planets, in a form of asymmetric ring circles around the star.
  • Solar Cycle - 24 - Solar Cycle — 24 is the 24th solar cycle since 1755, when recording solar sunspot activity began. It is the current solar cycle and started on January 4, 2008, but there was minimal activity until early 2010. In May 2009, the NOAA weather forecast Solar Cycle 24 panel predicted the cycle to peak at 90 Sunspots in May 2013..

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