Good morning Image courtesy: flickr.com Every night when we go to bed we are sure the sun will rise the next day, and the next, and the next. Yes, sun has been a constant in our lives and we are very confident that it will still be there as we grow up and grow old. Our sun is very special to us. Our sun, our very own special star. We on Earth depend so much on our sun for its heat, for the light. Our plants grow because of the energy from sunlight. We get energy when we play and go about our daily lives under the sun. Our climate, our weather, everything depends on our sun. Our sun is a yellow dwarf star and is located about 150,000,000 kilometers away. We now know from our first exercise how far each planet is from the sun and each other. Other stars are even farther away. Astronomers thought that it would be too cumbersome to keep writing these long numbers all the time so they decided to standardize distances in space with a “unit”. The distance between our Earth and our Sun was to be taken as one astronomical unit (AU) and all distances in the solar system are measured by this unit. (beyond the solar system distances are measured by light years) Therefore 1AU = 150,000,000 km It takes approximately 8 minutes for light to travel from our Sun to Earth. So when we look at our sun at this moment (warning- do not look at the sun directly with unprotected eyes - view only through dark UV protection glasses), we are actually seeing how it was 8 minutes ago. How old is our Sun and how did it come into existence. Our Sun is a gassy star and was created just like other stars. Our sun was “born” about 4.57 billion years ago from a molecular cloud that consisted of helium and hydrogen. While smaller parts of the cloud became planets a huge chunk of the cloud rotated. As it rotated, the clouds gathered closer and closer together at the center forming the core. The tighter the core became, along with the high rotation, a lot of pressure and gravity at center generated high temperatures. As the heat and gravity pulled in more of the matter around it, the cloud became hotter till the temperatures reached so high it triggered nuclear fusion and our Sun was formed. It took about 100 million years for our Sun to form. The Sun’s gravity holds the solar system together. How is it within the Sun? Image courtesy: study.com The sun has six regions: the core, the radiative zone, and the convective zone in the interior; the visible surface, called the photosphere; the chromosphere; and the outermost region, the corona. At the core, the temperature is about 15 million degree Celsius. This high temperature causes atoms to combine to form larger atoms – the process is called thermonuclear fusion. Thermonuclear fusion releases staggering amounts of energy. In the sun's core, hydrogen atoms fuse to make helium. The energy produced in the core powers the sun and produces all the heat and light the sun emits. Energy from the core is carried outward by radiation, which bounces around the radiative zone, taking about 170,000 years to get from the core to the top of the convective zone. In the convective zone, the temperature drops below 2 million degrees Celsius, where large bubbles of hot plasma (a soup of ionized atoms) move towards the photosphere. Photosphere :The surface of the sun — the part we can see — is about 5,500 degrees Celsius. Although this temperature is much cooler than the temperature at the core – 5,500 degrees C can boil diamonds to a liquid - like a pot of soup. The photosphere, is 500-kilometer-thick. Most of the sun’s radiation escapes here which we see as sunlight when it reaches Earth eight minutes later. Atmosphere The sun’s atmosphere is made up of chromosphere and the corona. This is where sunspots and solar flares occur. Magnetosphere The sun has a huge magnetic field that extends through a very vast expanse in space. These magnetic currents are carried through space known as solar winds and the area this magnetic field occupies is called the heliosphere. (More on this later) The sun is never quiet. Every eleven years or so it wakes up when its magnetic poles shift their polarity. This causes lot of disturbances to the photosphere, chromosphere, and corona. Known as the solar maximum this is storm season on the sun. The storms on the sun are sunspots, solar flares, and coronal mass ejections which carry a huge amount of energy and particles. Sunspots Image courtesy :NASA **** Solar flare Image courtesy: NASA Coronal mass ejection: Image courtesy:SOHOWWW.nascom.nasa.gov When these energy and particles reach Earth they can damage our satellites, and affect our power and communication grids. The Sun rotates differentially. Since the sun is not solid and only gas, different regions rotate at different speeds. At the equator it completes one rotation in 25 earth days and at the poles it complete one rotation in 36 days. Our Sun has now reached middle age and is expected to live for another 5 billion years. The end will come when it uses up all its hydrogen to form helium. The sun will then expand – consuming Mercury, Venus, and Earth - and then collapse, then undergo all sorts of violent changes before ending up a white dwarf till it burns itself out. Here is an interesting live video of our active Sun: Information sources: Universe today, NASA, Space.com, www.astro.ufl.edu
M Ma'am i have a question , sun wakes up every 11 years and can damage our satellites , means are our satellites built for 11 years or the satellites are built in a way that can survive the damage . plz reply News in India is that ISRO is planning to launch 83 satellites at a time in the space and break the record for so far!
