Ever wondered why stars have different colours and sizes in the night sky? If you haven’t noticed this before, take a moment to look up and ask yourself, why are some stars brighter than others? Why do some appear larger than others?

Let’s explore these questions together.

The temperature and size of a star

A star’s temperature is directly linked to its size. Larger stars contain more gas, which means more fuel. The more fuel a star has, the hotter it burns.

Blue stars

While colour blue has a soothing and cooling effect on us, it is actually the colour of the hottest stars in the universe, reaching temperatures of up to 40,000 degrees Celsius. Blue stars emit ultraviolet light, which is why they appear blue to our eyes.

They are huge and exist for a short period before exploding in a supernova, resulting in the release of elements like carbon and oxygen into the universe, which are then used to form new stars.

Red stars

Well, red symbolises fire and heat, but in the earthly context. In the deep cosmos, red stars are the coolest and emit a deep red light with surface temperatures around 3,000 degrees Celsius. Red stars live for a super long time, like trillions of years! They also have strong magnetic powers that can cause big space explosions.

White stars

White stars are super-hot, but not as fiery as the blue ones. They shine with a bright bluish-white glow. Unlike our Sun, they’re younger and don’t live as long.

Scientists measure how bright stars are, by using a special number scale called “apparent magnitude.” Lower numbers mean brighter stars. White stars are like the measuring sticks for this scale. Astronomers compare other stars to white stars to figure out how bright they are.

Yellow and orange stars

Yellow stars are medium-sized and give off a yellow light. They usually live for about 10 billion years. Yellow stars are the most common type of stars and often have planets orbiting around them. While orange stars are actually reddish-orange and are cooler than yellow stars.

Orange stars live for a really long time — about 20 to 30 billion years! According to scientists, orange stars are the best places to find planets where life might exist.

Our Sun is actually white!

Our Sun looks bright yellow, but that’s because of the interference of the Earth’s atmosphere. The sun is a yellow dwarf, but actually really white.

The twinkle of the stars

This mesmerising effect of twinkling of the star is caused by Earth’s atmosphere. As starlight passes through our planet’s atmosphere, it gets distorted, making the stars appear to flicker and change colour — hence the twinkle!

Why do stars look white?

Our eyes contain special cells that enable us to see colours. These cells require ample light to function effectively. Since stars are incredibly distant, the amount of light reaching our eyes is limited. As a result, we primarily see stars as white.

Interestingly, our eyes adapt to changing light conditions. In low light, the colour-detecting cells in our eyes become less active, making objects appear less colourful. This is why the world seems to lose its vibrant hues as night approaches.

Seeing coloured stars

You may not believe, but the time of the year also matters when observing the colours of the stars in the night. For instance, winter skies often have the best coloured stars. Usually, bright lights from cities make it hard to see stars and their colours. So, it’s better to look at the stars from a dark place.

If you really want to observe the night sky with the shimmering colourful stars, you must make sure that your eyes are quite accustomed to the darkness for some time before you sit peacefully to gaze. This helps your eyes see better in the dark.

Published in Dawn, Young World, August 17th, 2024