Solar system definition
- 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.
- 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
- 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.
Stars in the sky
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 .
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.
MUST READ : Important International Days and their Theme
The Universe facts
- ALMA – The Atacama Millimeter Array is an astronomical radio telescope interferometer in Northern Chile’s Atacama Desert.
- 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..