[Lewis Thomson (OP)]

Listener Michael wrote in to ask this question.

"What makes stars twinkle and what can their colours tell us about them?"

Do you also wonder what twinkling stars are after singing the lullaby. Discuss in the comments below...

[Janus]

The twinkling you see in stars when you look up at them from Earth is caused by atmospheric interference. (the reason the Hubble was able to get such good pictures, even though being smaller than many Earth-bound telescopes was that it was above the atmosphere.
The color of the stars tells us their spectral class, and thus their temperature.  Red stars are the coolest, then orange, yellow, yellow-white, white, and blue-white.

[evan_au]

Humans can only detect 3 broad bands of colour - red, green and blue.

However, with an instrument called a spectroscope, it is possible to break up the light of a star into thousands of narrow colour bands (advanced ones can go to millions of colour bands).
- With this information, it is possible to determine the chemical composition of the star, and its temperature
- With the more advanced instruments, it is possible to detect planets orbiting a distant star, because the gravitational tug of the planet causes a Doppler shift of the star's light, as the planet orbits the star.

humans will never be able to understand the chemical composition of planets, let alone the stars

In the 1860s the husband-and-wife team of William and Margaret Huggins used spectroscopy to determine that the stars were composed of the same elements as found on earth.

See: https://en.wikipedia.org/wiki/Spectroscopy