Some basic facts about the sun – our host star

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

06 February 2022

Githuku Mungai has been reading some material about the Sun and other stars. He doesn’t say which publication it is, but I suspect it is the Internet. He came across some statements and was wondering if they are true.

The first one said: “Every star you see in the night sky is bigger and brighter than our sun.” This is not exactly true. With the unaided eyes, we can see at least three stars that are smaller than the sun. But let me reiterate: this is when looking at the sky from the ground on earth. There are many billions of stars smaller than the sun but you can’t see them without a telescope…and from above the atmosphere.

 Githuku’s second statement was: “You can't see millions of stars on a dark night.” This one is true. On a clear cloudless night and far away from the glare of city lights, only about 3,000 to 4,000 stars can be seen with the unaided eyes. Indeed, in one of the learning activities in the new Competency Based Curriculum (CBC), grade 3 children are asked to go out at night and count the stars. The results are usually shocking even to the teachers: no child in Nairobi has ever counted more than 50 stars!

Thirdly, Githuku read that “Our sun is a green star.” This is false. The colour of the sun is certainly not green! We all know that, don’t we? Unfortunately, the only times that the sun is dim enough to look at is at sunrise and sunset. At those times, it appears reddish-yellow. For that reason, people assume that it is yellow.

The truth is that the sun is actually white! Sir Isaac Newton (yes, he of apples and gravity) was the first person to pass a beam of sunlight through a glass prism. He observed that the light splits into a band of many uncountable colours starting from Red to purple/violet – similar to a rainbow.

Because of his superstitious beliefs on the special nature of the number seven (seven days of the week, seven musical notes and so on), he decided to assign seven names to the continuous band of colours. The truth is that there are infinitely many colours and, when they all combine, they are seen as white. So, the sun is white.

Why does it appear yellow at sunrise and sunset? That’s a story for another day.