Twinkle, twinkle, little star…
How I wonder… why you look red?!
If you look at stars through a telescope, you might notice that some of them seem to shine red, yellow, or blue!
So here’s a curious question:
Why are stars different colors?
The short answer is: because of their temperatures.
temperatures
Stars are huge balls of gas.
And they’re all hot—very hot!
But some are hotter than others.
A star’s temperature is determined by lots of things, like its age...
mass
And its mass—in other words, how much gas it contains.
And stars of different temperatures appear to be different colors.
Betelgeuse
For example, this is Betelgeuse.
3,200°C
The surface of Betelgeuse is 3,200 degrees Celsius.
That’s 32 times as hot as boiling water—so it’s pretty hot!
But compared to some stars, Betelgeuse is actually fairly cool.
Sirius
Let’s take a look at Sirius.
9,700°C
Its surface is around 9,700 degrees Celsius, which is 97 times as hot as boiling water!
the Sun
And what about our nearest star, the Sun?
5,500°C
Its temperature is somewhere in the middle, around 5,500 degrees Celsius—or 55 times as hot as boiling water.
What do you notice about the colors of these stars?
Betelgeuse
A cooler star, like Betelgeuse, looks kind of red...
Sirius
While a hotter star, like Sirius, looks kind of blue.
the Sun
And an in-between star, like our Sun, looks kind of yellow.
To recap: A star’s color is determined by its temperature.
Cooler stars look red, while hotter stars look blue.
Our Sun is in-between—so it looks kind of yellow!
Got it? Great! Another Curious Question answered.