Why Stars Have Different Colours
A starās colour is determined by its surface temperature:
Blue stars: Extremely hot
White stars: Very hot
Yellow stars: Medium temperature (like the Sun)
Red stars: Cooler
Colour is not cosmetic ā it tells astronomers how a star behaves and how long it will live.
Stellar Classification
Stars are classified using the OBAFGKM system:
O & B: Massive, blue, short-lived
A & F: White, moderately massive
G: Yellow stars like the Sun
K & M: Red dwarfs, long-lived
Red dwarfs are the most common stars in the universe and can burn for trillions of years.
The HertzsprungāRussell Diagram
Astronomers plot stars on the H-R diagram, which compares:
Brightness
Temperature
Most stars spend the majority of their lives on the main sequence, where they steadily fuse hydrogen.
Size vs Lifespan
Counter-intuitively:
Bigger stars live shorter lives
Smaller stars live longer
Massive stars burn fuel at an enormous rate and may last only millions of years, while small stars can outlive the current age of the universe.
Key Takeaways
Colour indicates temperature
Mass determines lifespan
Most stars are red dwarfs
The Sun is a middle-aged star