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What is the Sun?

The Sun (or Sol), is the star at the center of our solar system and is responsible for the Earth’s climate and weather. The Sun is an almost perfect sphere with a difference of just 10km in diameter between the poles and the equator. The average radius of the Sun is 695,508 km (109.2 x that of the Earth) of which 20–25% is the core, a sphere composed primarily of the two gases Hydrogen and Helium such that certain conditions are met.

How the Sun is a star?

The first condition is that it must have a mass falling within a certain range. Though debated, this range is generally accepted to be between approximately 1.4 x 10^29 kg and 3.0 x 10^32 kg.

The second and most important condition is that nuclear fusion must be present. Nuclear fusion is the process whereby two lighter atomic nuclei join or “fuse” together to produce a heavier atomic nucleus. In the context of stars, hydrogen is the lighter and helium the heavier.

Size of the Sun

The size of the Sun compared to the largest known stars (Red Giants) is not very big. However, if compared to the most common type of star in the universe, the red dwarf, the Sun is quite a bit larger.  The average radius of the Sun is 695,508 km (109.2 x that of the Earth). Thus, the Sun is not the biggest type of star in the universe, but it is definitely larger than most.

Some facts about the Sun
  • The Sun accounts for 99.86% of the mass in the solar system.

  • The Sun is almost a perfect sphere – Considering the sheer size of the Sun, there is only a 10 km difference in its polar and equatorial diameters – this makes it the closest thing to a perfect sphere observed in nature.
  • The Sun is all the colors mixed together, this appears white to our eye – To our eyes, in space, the sun would appear white, not yellow.
  • The Sun is halfway through its life – At 4.5 billion years old, the Sun has burned off around half of its hydrogen stores and has enough left to continue burning hydrogen for another 5 billion years. Currently, the Sun is a yellow dwarf star.

  • The distance between Earth and Sun changes – This is because the Earth travels on an elliptical orbit path around the Sun. The distance between the two ranges from 147 to 152 million km. This distance between them is one Astronomical Unit (AU).
  • It takes eight minutes for light reach Earth from the Sun – The average distance from the Sun to the Earth is about 150 million km. Light travels at 300,000 km per second so dividing one by the other gives you 500 seconds – eight minutes and twenty seconds. This energy can reach Earth in mere minutes, but it takes millions of years to travel from the Sun’s core to its surface.

  • The Sun is traveling at 220 km per second – It is around 24,000-26,000 light-years from the galactic center and it takes the Sun approximately 225-250 million years to complete one orbit of the center of the Milky Way

  • Temperatures inside the Sun can reach 15 million degrees Celsius.

  • The energy created by the Sun’s core is nuclear fusion – This huge amount of energy is produced when four hydrogen nuclei are combined into one helium nucleus.

  • About 30% of solar radiation is reflected back to space and the rest is absorbed by oceans, clouds, and landmasses.

  • In February 1974, Skylab was the first manned spacecraft to study the Sun.
  • The star that’s closest to our sun, Proxima Centauri, is still much farther away than Pluto (4 light-years distance).

  • A bolt of lightning is 5 times hotter than the surface of the sun.

  • If you weigh 100 lbs, your weight on the Sun would be 2707 lbs. (multiply your actual weight by 27).

  • The Sun does not have a definite boundary, and in its outer parts, its density decreases exponentially with increasing distance from its center.

  • The Sun rotates in the opposite direction to Earth with the Sun rotating from west to east instead of east to west like Earth.

  • One day the Sun will consume the Earth – The Sun will continue to burn for about 130 million years after it burns through all of its Hydrogen, instead of burning helium. During this time, it will expand to such a size that it will engulf Mercury, Venus, and Earth. When it reaches this point, it will have become a red giant star.

  • The Sun will eventually be about the size of Earth – Once the Sun has completed its red giant phase, it will collapse. Its huge mass will be retained, but it will have a volume similar to that of Earth. When that happens, it will be known as a white dwarf.

  • The outer layers of the Sun exhibit differential rotation – At the Equator, the surface rotates once every 25-25.4 days; near the poles, it’s as much as 35-36 days. This odd behavior is due to the fact that the Sun is not a solid body like the Earth. Similar effects are seen in the gas planets. The differential rotation extends considerably down into the interior of the Sun but the core of the Sun rotates as a solid body.

  • Every day, plants convert sunlight into energy equivalent to six times the entire power consumption of human civilization.

  • In 1666, Sir Isaac Newton observed the Sun’s light using a prism and showed it is made up of light of many colors.

  • Apart from HEAT and LIGHT, the Sun also emits a stream of CHARGED PARTICLES called the SOLAR WIND. The Solar Wind:-
    –Causes Radio INTERFERENCE at certain times
    –Causes the characteristic TAILS of COMETS.

  • The Sun rotates more quickly at its equator than it does close to its poles. This is known as differential rotation.

  • All of the world’s energy needs can be met with 1/10,000th of the light from the Sun that falls on Earth each day, according to the inventor Ray Kurzweil.

Take the quiz about the Sun

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