Have you ever looked up at the stars at night and wondered why some are white while others are yellow or red? Star color gives us valuable information about its physical properties. In this article, we will explore what color are the hottest stars.
There are five colors of stars that are ranked from hottest to coolest. They are blue, blue-white, yellow, orange, and red. While you may think that the hottest stars would be red and the coolest blue, it is quite the opposite.
Blue stars have a surface temperature of around 25,000 Kelvin, whereas a red star’s surface temperature may be only 3,000 Kelvin.
These five are the main star colors but there are in-between colors too. Color classes are O (blue), B (bluish), A (blue-white), F (white), G (yellow-white), K (orange) and M (red).
This classification is called the Morgan-Keenan System, which is based primarily on surface temperature. More specifically, it is based on spectral type and luminousity. This classification system is summarized in the diagram below.
According to this classification, white stars have an approximate surface temperature of 10,000 Kelvin, yellow stars 6,000 Kelvin and orange stars 4,000 Kelvin. Blue stars can have a surface temperature of between 10,000 and 50,000 Kelvin.
Blue stars are much hotter than our sun, which is a yellow star. They are also much larger, between 12 and 25 solar diameters. On the other hand, red main sequence stars are only 0.1 to 0.6 solar diameters and are much cooler.
So, What Color Are the Hottest Stars
As you may have already gathered, the color of the hottest stars is blue.
Now that we have answered the question directly, we will consider some factors related to the color of stars
What Affects Star Color?
Star colors differ depending on where you are observing them from. They look different when viewed through the Earth’s atmosphere, mainly appearing white or bluish.
This is because they are too distant for us to see their colors.
When we see images of stars from Hubble or the James Webb Space Telescope, we assume that the stars have had color added to them. But in actuality, stars are more colorful and vibrant than we imagine.
However, even space telescopes don’t always detect stars’ true colors. As very distant stars move away from an observer, they are red-shifted due to the Doppler effect.
Cosmic dust can also distort a star’s true color as it scatters and absorbs light. Dust scatters blue light more than red light, making stars look redder than they really are.
This is called interstellar reddening.
The chemical or metallic composition of a star also affects its color. Carbon-rich stars have molecules that absorb violet and blue light, making the stars turn a deep red.
Not all the factors that affect star color come from the cosmos. Human vision is more sensitive to blue light than red light, so we tend to see more blue stars than red ones.
Although some modifications can be made to a star’s color, it is its surface temperature that has the most effect on its color.
What Color Is The Sun?
The sun appears white when viewed from space. This is because its apparent color is actually an average of all emitted wavelengths, including blue and red.
Sunlight appears yellow from the surface of the Earth due to the scattering of blue light by the atmosphere.
At sunrise and sunset, the sun appears more orange and red as the scattering caused by the planet’s nitrogen molecules is more pronounced.
This is because the shorter wavelength colors of blue, green and violet are scattered leaving the longer wavelengths of red, orange and yellow.
Why Are Stars Different Colors?
We’ve all seen different elements burn with varying intensities and colors during science class or added salt to a fire to see the flame change color.
In a fire, the hottest part of a flame is the blue-white area, while the coolest is the red. The same is happening with stars.
Age also affects the color of stars. As they age, stars produce varying chemicals that ‘burn’ at different temperatures.
This is how it is possible to use a star’s color to determine its age.
Astronomers have devised quantitative methods to precisely define the colors of stars. They then use these colors to determine the stellar temperature.
Measuring a star’s apparent brightness through filters allows astronomers to specify the exact color of a star.
Star classification also typically indicates a star’s absolute brightness, with blue stars tending to be brighter than red stars.
However, this depends on the distance to the star, which can cause red stars that are closer to shine brighter than distant blue stars.
Color can often indicate a star’s size, with the largest stars being bigger and more energetic blue stars and smaller stars more likely to be red.
Red dwarfs are the coolest stars and are one of the most common stars in old galaxies.
However, a dying star that has consumed all of its hydrogen and helium will turn into a red giant. This occurs when the outer layers of the star expand and cool. Eventually, the star will expel its outer layers and become a white dwarf, neutron star or black hole, depending on the remaining mass.
What Color Stars Can You See?
We can see different colored stars from the Earth, but as we have mentioned, the colors we see from Earth are typically not true colors.
Some of the brightest stars, such as Sirius and Vega, look blue. Rigel in the constellation of Orion is blue-white, as is Spica in the constellation of Virgo.
One of the most prominent red stars in the night sky is Betelgeuse. Betelgeuse is a red supergiant in Orion. Astronomers believe it is nearing the end of its lifecycle and is close to going supernova. It is the ninth brightest star in the night sky, so it is very easy to spot. It’s also one of the largest known stars, with a diameter a thousand times larger than our sun.
Capella in the constellation of Auriga is a yellowish star, and Arcturus in Boötes is a golden color.
But all of these colors are just the tip of the stellar iceberg. If our eyes could see the true colors of stars the night sky would be a veritable rainbow of color.
Relationship between Star Color And Length of Life
We have discovered that blue stars have a high surface temperature, while red stars have a much cooler surface temperature. Surface temperature is a function of a star’s mass. Blue stars are large, while red stars are smaller. Of course, we are ignoring those stars near the end of their lives.
As a consequence of being larger, the cores of blue stars are much hotter and contain higher pressure. This results in blue stars consuming hydrogen at a much higher rate. Because of this, the largest of them may only live for 10 million years before becoming a black hole.
Hi, my name is Jason Anderson, and I am a Physics Professor. Ever since I was a kid, I’ve been fascinated with space, the universe, the moon, you name it. I spent hours and hours at the planetarium close to my hometown, wondering what else could be out in the universe.
Since then, I’ve been an avid stargazer and astronomer, and love nothing more than spending my time charting stars, observing planets, and finding constellations.
This is why I decided to start Telescope Guru. I only wish to share this fun pastime with the world. With this site, I hope to answer all of your questions relating to astronomy, telescopes, and stargazing.
