Technology
How hot is the Sun?
EVERYONE loves a bit of sunshine – there’s not much better than basking in the hot rays and catching a tan.
But the Sun is actually so hot that it takes just eight minutes for its heat to travel 147.5 million kilometres (92 million miles) to reach us. So what is the Sun’s temperature?
How hot is the Sun?
The Sun is a blistering 15 million degrees Celsius (27 million degrees Fahrenheit) at its very centre, known as its core.
The hottest parts of the Sun are its core and its outermost layer.
The temperature has been known to drop to between two and seven million degrees C in the next layer of the core, the radiative zone.
And the heat of the Sun is even lower – under two million degrees – at the third and final layer of the Sun’s core, the convective zone.
The temperature has dropped to 5,500 degrees C in the photosphere – its visible “surface – and can drop as low as 4,000 degrees C in the middle of big sunspots in this layer.
Average temperature is about 4,300 degrees C in the next layer, the chromosphere.
But when you reach the outermost layer, the corona, the temperature rises again to between one million and ten million degrees C – almost as hot as the inner core.
In the corona, temperatures are often around two million degrees C, but spike up to 10 million in bursts of solar wind and magnetic energy.
The Sun is the only star in our solar system – but is actually average-sized compared to some other stars in the universe[/caption]
How big is the Sun?
The sun is a staggering 1.4 million km wide (865,370 miles) in diameter, i.e. across the middle – the width of 109 Planet Earths.
The circumference of the Sun is 4.4 million km (2.7 million miles) – it is almost a perfect spherical ball in shape.
The sun is the biggest object in our solar system.
More than one million Earths, 1,000 Jupiters, or more than 21.2 million Mercuries could fit inside the sun if it was hollow.
It also has the greatest mass – indeed, the Sun contains 99.86% of all of the mass in the solar system.
But there are billions of stars even bigger than our Sun, which is at best average size for a star.
For instance, Betelgeuse, which is usually the tenth-brightest star in our sky, could fit as many as eight billion of our sun inside it if it was hollow.
What is the Sun made of?
The Sun is a massive ball of plasma, which is super-hot gas. It is made up of 91 per cent hydrogen, and 8.9 per cent helium.
The hydrogen atoms at the centre, the innermost core, of the Sun, are so heavily compressed by gravity that they producing helium, in a process called nuclear fusion.
That nuclear reaction is what gives the heat and light energy of the sun.
The energy travels through all the remaining layers of the sun and eventually throughout our solar system.
The sun has three layers: core – made up of the inner core, radiative, and convective zones – as well as the atmosphere, and the corona.
The planets in our solar system all orbit around the Sun[/caption]
Energy made in the centre bounces around in the radiative zone for up to 100 years, because the plasma is so dense.
The convective zone, the next layer out, is made of larger plasma bubbles which move up and down in convection currents.
The Sun’s atmosphere is made of the photosphere and the chromosphere.
The energy passing through the photosphere is the sunlight that we see on Earth. This is the brightest layer.
We can’t usually see the chromosphere, the next layer out, because the photosphere is so bright.
But the large amount of hydrogen that makes up the chromosphere gives the sun its red rim in a solar eclipse.
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The final layer of the sun is the Corona, it is an ora which is also visible in a solar eclipse.
The sun is actually white, but the light is filtered by our own atmosphere so we only see the warm yellow part of the spectrum.
The nuclear reaction at its core that provides the sun’s heat and light is also causing the sun to get bigger and hotter, it will eventually burn up.
