KERALA PSC / ASTRONOMY / SUN / NOTES

 

KERALA PSC / ASTRONOMY / SUN / NOTES

KERALA PSC / ASTRONOMY / SUN / NOTES

 

·       The largest body of the solar system is the Sun and it is the centre of the solar system. This view was first put forward by Copernicus

·       The sun contains four parts: They are the Core, Photosphere, Chromosphere, Corona

·       The Core: the Sun’s core has a very high temperature and pressure. Temperature is roughly 15 million °C. At this temperature, nuclear fusion occurs, turning four hydrogen nuclei into a single helium nucleus plus a lot of energy

·       The Photosphere is the lower atmosphere of the Sun and the part that we see (since it emits light at visible wavelengths). This layer is about 300 miles (500km) thick. The temperature is about 5500°C.

·       The Chromosphere: This reddish layer is an area of rising temperatures. The temperature ranges from 6000°C (at lower altitudes) to 50000°C (at higher altitudes). It appears red because hydrogen atoms are in an excite state and emit radiation near the red part of the visible spectrum. The Chromosphere is visible during solar eclipses.

·       The Sun is made up of hydrogen (71%) helium (26.5%) and carbon (2.5%). Hydrogen is being converted to helium in the sun. This process is called nuclear fusion

·       Sun has the energy for 500 crore years of burning. After this, it will contract with Gravitational force and will become a red giant. And it will continue at this state for, 100 crore years and then become a planetary nebulae. After 35000 years it will evolve as a white giant. It then slowly releases energy from its outer layer and cools. It then becomes an invisible black dwarf

·       The distance between the Sun and Earth is shortest on 3^rd January

·       Orion Arm: the region in the milky way where sun is situated

·       Solar winds: A less spectacular but persistent streams of portions blowing out of the corona and sweeping over the whole Solar system are called Solar Winds. They are made up of Plasma, ie, ionized gas mostly hydrogen and helium.

·       The surface of the sun changes continuously Bright spots called Plages and dark spots called Sunspots frequently form and disappear

·       Sunspots: Sunspot appear dark because they are cooler by about 1500°C than the surface of the sun which has a temperature of about 6000°Celsius. The life periods of these spots also vary. They may last a few hours to many weeks. These sunspots show strong magnetic fields and reach a maximum every eleven years. They affect global atmosphere and climate and interrupt radio communications

·       NASA & European Space Agency together launched Ulysses to study the poles of the sun and interstellar space above and below the poles.

·       Solar Dynamics Observatory

Ø NASA launched the Solar Dynamic Observatory (SDO) on February 11, 2010 to observe sun and to study the suns influence on Earth.

 

KERALA PSC / ASTRONOMY / SUN / NOTES