What Color Is The Coolest Star?

What color is the coolest star

If you have ever looked up into the night sky, you will have seen the wonder of all of the stars, and constellations. Although we can spot stars with the naked eye, you may not be aware that stars can be different colors. 

Many people are unaware that stars can actually be red, blue, white, brown and even purple! However, we cannot see these colors without the help of telescopes or other instruments.

So, what exactly is a star? Why are stars different colors, and what color is the coolest star? These are the questions that we are here to answer! 

What actually is a star?

A star is a celestial body made up of mainly hydrogen and helium. As stars are made up of these components, they produce a lot of heat and therefore a lot of light, from the nuclear forges inside of them. 

In its most basic sense, a star is an extremely hot ball of bright, glowing hot matter out in space. It is because of the immense heat that stars produce that we see them as bright lights in the night sky. 

Why are stars different colors?

Just like many things in our universe, stars come in various different shapes and sizes. Stars even come in different colors! These colors can vary from yellow, orange and red, to blue, white and can even appear green. 

So, why are stars different colors? The main reason that stars will burn in varying colors and tones is because of its composition and the temperature of the star.

At all times, a star will emit lights, which is mainly a combination of different types of wavelengths. These various different wavelengths can affect how the color of the star looks to us. 

For instance, the hottest stars are closer to the blue colors on the spectrum, because they emit more light at shorter (blue) wavelengths. Whereas the cooler stars put out longer (red) wavelengths.

In addition, the hotter the star is, the more its radiated energy increases, and the further along the color spectrum it is pushed, and vice versa.  

What color is the coolest star?

As previously mentioned, the hotter the star is, then the further along the color spectrum it goes, and as stars become hotter in temperature, they move closer towards bluish hues.

This works in the same way as when stars are cooler. When stars are lower in temperature, they move down the color spectrum towards red and warm hues.

Therefore, the very coolest stars will be red in color. As they warm slightly, they may become yellow or orange, and then again they will turn to white as they become hotter. 

What color is the hottest star?

If the coldest stars in the universe are red, then it is clear that the hottest stars will be opposite on the color spectrum. The hottest stars are therefore blue in color.

Stars that are hotter in temperature will range from white colors to blue white, and deeper blue tones. The hottest stars of all will be very blue in color, however you may not be able to see this with the naked eye. 

What is the hottest star in the universe?

To some people’s surprise, the Sun is not the hottest star in the universe. The hottest known stars in the universe are blue hypergiant stars.

These are huge stars with more than 100 times the mass of the Sun, and some are located over 7,500 light years away from the Sun itself. 

We can understand which stars are the hottest, and which colors they appear by classifying them into various different types. For instance, stars are classified with spectral types.

These types are given letters in order to identify them, starting with O, B, A, F, G, K and ending in M. 

In general, O stars are considered the hottest, as these burn with temperatures from about 20,000K all the way up to 100,000K. Due to their extremely high temperatures, these types of stars will almost always burn out within a few million years. 

The second hottest types of stars are B stars, with temperature starting at 10,000K and as high as 20,000K. Although these stars are not classified as the hottest in the universe, they are still noticeable blue in color. 

Then, we have A stars, which burn between 8,000K and 10,000K. These types of stars will appear white in color, and are followed closely by F stars. F stars are stars that are only just slightly hotter than the sun.

Then, there are G stars, at 5,000K and 6,000K. These stars appear yellow in color, just like the Sun, which is classified as a G star. 

Following this, there are K stars, which are orange in color, and burn between 3,000 and 5,000K. The coolest stars in the universe are classified as M stars.

These are much cooler as they have molecules including water and carbon monoxide, and are more noticeable red in tone. 

Can you get green and purple stars? 

Whilst most stars are classified as either white, blue, red, orange or yellow, some people may have looked through a telescope into the night sky, and seen a purple or green star. 

These are not actually purple or green in color, they simply appear that way. Purple and green stars are actually just white or bluish colored stars that look green to us, because of the way our eyes perceive visible light. 

Gordon Watts
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