The Sun Earth
The Sun it is one of the stars in the Milky Way galaxy. It takes 224 million years to complete one circle (revolution) around the galactic circle (called cosmic year).
The sun is 109 times bigger than the earth and weighs 2′ 1027 tons.
Its glowing surface, which we see, is called photosphere. Above the photosphere is the chromosphere. Beyond chromosphere is the corona which is visible during eclipses.
The core of the sun has the temperature about 15 million degrees K.
Superimposed on sun’s white light are hundreds of dark lines called Fraunhofer lines. Each line indicates some element present in the solar atmosphere.
The sun is constantly emitting streams of its substance (mainly hydrogen) as protons in all directions. Sometimes these emissions are massive. Such emissions are called Prominences.
Sometimes these emissions roll out of the atmosphere of the sun for thousands and thousands of miles, when they are seen as Solar Flares.
A persistent stream of protons and electrons is blowing out of the corona and sweeping over the whole solar system. This stream is called Solar Wind.
The earth’s magnetosphere acts as a shield against the ever-blowing solar wind and deflects it away from the earth. Nevertheless, particles of solar wind sometimes pierce the magnetic shield and enter the upper atmosphere, where, like the solar flares, they cause auroral displays.
In the Arctic region, they are called Aurora Borealis and in the Antarctic region, they are known as Aurora Australis.
The surface of the sun changes continuously. Bright spots called Plages and dark spots called Sunspots occur there.
Sunspots appear dark because they are cooler, i.e., they have a temperature of about 1500″C. Sunspots have a periodicity of 11 years.
The energy of sun comes from the fusion of hydrogen into helium.
Sunlight takes 8 min, 16.6 sec to reach earth.
Ecliptic is an imaginary annual path of Sun across the sky.
Its age is 5 billion years and the total life is 10 billion years.
The Sun Some Facts
- Average distance from Earth to sun – 14,95,98,900 km
- Sun Diametre – 13,91,980 km
- Temperature at Core – 1,50,00,000″ C
- Temperature at Photosphere – 5,760″ C
- Rotation Period – 25 days (at equator), 33 days (at poles)
- Chemical Composition – Hydrogen 70%, Helium 28%, Others 2%
- Age – 4.6 billion years (approx.)
- Expected Life – 10 billion years (approx.)
- Time taken by light to reach from Sun to Earth – 8 min 16.6 sec.
- Velocity of light (in vacuum) – 3,00,000 km/sec.
- Gravitational Pull – 28 times than that of Earth