We all know about the Sun and its importance to us. Sun is the source of energy that sustains all living systems and drives life. It helped to create us and sustain us. Without it life would never have existed on the Earth. However big picture of the Sun is not known to everyone – let’s find out more about our closest star – the Sun.
Sun has a diameter of approximately 864,000 miles which is about 109 times the diameter of Earth. One hundred and nine Earths would be required to fit across the Sun’s disk, and its interior could hold over 1.3 million Earths. [#1]
Sun’s Activity
The Sun shows evidence of sudden releases of energy. One of the most commonly observed events are solar flares or Sun spots. All of these types of solar activity are assumed to be driven by energy release from the solar magnetic field. The amount of solar activity on the Sun is not even and is directly related to the number of Sun spots that are visible. Research is going on to find out how this energy releases occur and what are the relationships between different types of solar activity.
Zones of Sun
The Sun and its atmosphere consist of a number of zones. Starting from inside, the Sun interior consists of the core, the radiative zone and the convection zone. The solar atmosphere is made up of the photosphere, the chromosphere, a transition region and the corona. Outside the corona is the solar wind, which is actually the flow of coronal gas into space.
How Sun produces light
The core contains about half the Sun’s mass and roughly all the fusion in the Sun takes place in the core. It is here that the temperature and pressure is so intense that nuclear reactions take place. As nuclei have a positive charge, they tend to repel each other. However the core’s temperature and pressure are high enough to force nuclei together. This fusion reaction causes four protons or hydrogen nuclei to combine together to form one alpha particle or helium nucleus. The alpha particle produced is around 0.7 % less massive than the four protons. This difference in mass is released as energy, which is carried to the surface of the Sun through convection, where it is released as light and heat.
The solar radiation reaches Earth in three wavelength spectra. The Sun emits 44 % of its radiation in the visible spectrum, 7 % in the ultraviolet spectrum (short wave) and 49 % in the infrared spectrum (long wave).
Life of the Sun
The Sun is believed to be active for 4.6 billion years and has sufficient fuel to go on for another five billion years or so. At the end of its life, the Sun will start to fuse helium into heavier elements and begin to swell up; finally growing so large that it will gulp the Earth. After a billion years as a red giant, it will abruptly collapse into a white dwarf. It may take a trillion years to cool off completely.[#2]
Solar Eclipses
Solar eclipses take place when the Earth passes through the Moon’s shadow. A total solar eclipse occurs only in a new moon, when the Moon passes in a direct line between the Sun and the Earth.
When a total eclipse occurs, the Moon’s shadow covers just a small portion of the Earth, where the eclipse is visible. As the Moon moves in its orbit, the location of the shadow changes accordingly. Hence total solar eclipses typically only last a minute or two in a given location.
Sun’s effect on us
The total radiation given off by the Sun alters with solar activity like solar flares or sunspots. As the solar activity is considered to vary in cycles, like the 11-yr Sun spot cycle (and longer cycles), scientists have doubts if changes in our weather and climate might be linked with short or long term solar cycles. Lot of research is being done on the influence of solar variation on Earth’s climate, but there is mixed results. Changes in Sun spot cycles definitely change the amount of solar radiation given off by the Sun, but only by a little bit. However these changes aren’t sufficient to account for the majority of the warming observed in the atmosphere over the last half of the 20th century.
If you would like to learn more about the relationship between solar variation and climate, visit the Intergovernmental Panel on Climate Change’s Frequently Asked Questions section of their recent report.
References:
[#1] issuu.com/linkahwai/docs/solarobserver1
[#2] www.solarviews.com/eng/sun.htm
[Images] www.nasa.gov
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