ASTRONOMY 101: THE SUN

The Sun is an ordinary star and is the brightest object in our sky.  As such you should certainly never look at the Sun directly and certainly never through binoculars or a telescope.

It’s one of more than one hundred billion stars that populate our Milky Way galaxy.  It’s a gigantic ball of hydrogen 870,000 miles wide.  The Sun has a diameter 109 times that of the Earth and is one third of a million times its mass.

The Sun collapsed from a cloud of hydrogen gas approximately 4.5 billion years ago.  The pressure and temperature of the hydrogen in its centre became so great that nuclear fusion chain reactions started where 600,000,000 tons of hydrogen are converted into helium each second.  In the process, under Einstein’s famous equation E equals M C squared, a small amount of mass is lost as energy including light.

This energy is what we and all living things depend on for our existence.  The visible light we see from the Sun takes eight minutes to travel the 93 million miles before it reaches our eyes and is only a small part of the energy released from our star.  Its nuclear reactions also produce vast quantities of ultra violet light along with deadly x-rays and gamma ray radiation.  Indeed if it wasn’t for the Earth’s protective magnetic field this radiation would strip off our life-giving atmosphere and all life on Earth would be burnt to a crisp.

Temperatures at the core of our star Sun reach a staggering 10 million degrees Celsius, but it’s surface is less hot at about 5,000 degrees Celsius.

The Sun consists of approximately 75% hydrogen and 25% helium and is halfway through its life.  In 4.5 billion years it will run out of its hydrogen fuel and will start to fuse helium into even heavier elements.  In the process it will become a bloated Red Giant star that will engulf the orbit of the inner planets.  Finally it will puff off its outer layers as a planetary nebula before contracting to the size of the Earth.  It will have become a white dwarf star made of pure carbon diamond… a cosmic ember.  I don’t think however we’ll be around to see it!

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