บทสนทนานี้ใช้ตอบคำถามข้อที่30-35

    In popular culture, the sun is yellow. However, in Japan most people think that it is red. Children there usually draw the sun as a big red circle. But did you know that the colour of the sun is actually white? It's only when light from the sun passes through the Earth's atmosphere that it changes in colour, from white, to the yellow most of us see here on Earth.

    All stars have colours, from red dwarfs and red giants, to white and yellow stars, to blue giants and supergiants. The colour of a star comes from its temperature, As photons escape the interior of a star out into space, they have different amounts of energy. A star can emit infrared, red, blue and ultraviolet light all at the same time. They even emit X-rays and gamma rays.

    If a star is cool, less than 3,500 Kelvin, its colour will be red. This is because there are more red photons being emitted than any other kind of visible light. If a star is very hot, above 10,000 Kelvin, its colour will be blue. Once again, there are more blue photons streaming from a star.

   The temperature of the Sun is approximately 6,000 Kelvin. The sun and stars like our sun appear white. This is because we're seeing all the different colour photons coming from the sun at the same time. When you add all those colours up, you get pure white.

So why does the sun appear yellow here on Earth? The atmosphere of the Earth scatters sunlight, removing the shorter wavelength light - blue and violet. Once you reduce those colours from the spectrum of light coming from the sun. it appears more yellow.

What is NOT emitted by a star?