The Colours and Temperatures of Stars 🌟

by Fiona

When we look up at the night sky, it’s easy to imagine that all stars twinkle with the same white light. But in reality, stars come in a stunning range of colours — from the coolest deep reds to the hottest brilliant blues. The colour of a star tells us a lot about its temperature, age, and even its life stage.

The Science Behind Star Colours

The colour of a star depends primarily on its surface temperature. Cooler stars emit more red light, while hotter stars give off more blue or violet light. Just like heated metal glows red, then orange, then white as it gets hotter — stars follow a similar pattern.

Astronomers classify stars according to both their colour (temperature) and luminosity (brightness) using the Morgan–Keenan (MK) system. This system divides stars into seven main spectral types:

Our Sun: A Typical G-type Star

Our own Sun is a G-type (G2V) star. It’s often called a yellow dwarf, though in truth, the sunlight it emits is nearly white when viewed from space. The Sun’s surface temperature ranges from about 5,200 K to 7,500 K (that’s roughly 4,900°C to 7,200°C). This moderate temperature allows Earth to bask in just the right amount of warmth to support life.

Beyond the Main Sequence

In addition to these seven main types, astronomers have discovered substellar objects that don’t shine brightly enough to be true stars. These are the brown dwarfs, classified under spectral types L, T, and Y.

  • L-type brown dwarfs are relatively warm (around 1,300–2,000 K).
  • T-type are cooler (700–1,300 K).
  • Y-type are the coldest known — some barely above room temperature!
    These objects are sometimes called “failed stars” because they don’t have enough mass to sustain nuclear fusion in their cores.

So, What About the Other Stars?

  • Blue stars (O & B types) blaze fiercely, shining millions of times brighter than the Sun — but they live fast and die young.
  • White and yellow stars (A, F, G types) are stable and long-lived, with many hosting planetary systems.
  • Orange and red stars (K & M types) are cooler and dimmer, but they can burn for trillions of years — far longer than our Sun.

🌠 Quick Quiz

Q. Which of the following stars is the coolest (Lowest temperature)?
A) Red Dwarf
B) Orange Star
C) Yellow Dwarf
D) Blue Star

Take your best guess, and let me know what you think!
**The first 10 correct answers sent to support@underluckystars.com will get a FREE Digital Star Map
**
Wishing you clear skies and cosmic dreams