You're likely thinking of the saying "rainbows after the rain," not stars! Rainbows are an optical phenomenon that occurs when sunlight shines through raindrops.

Here's how it works:

1. Sunlight: Sunlight is made up of all colors of the rainbow.

2. Raindrops: When sunlight enters a raindrop, it bends (refracts).

3. Reflection: The light then reflects off the back of the raindrop.

4. Refraction again: As the light exits the raindrop, it bends again.

5. Separation: This double refraction causes the different colors of light to separate, just like a prism.

6. Rainbow: The separated colors are what we see as a rainbow.

So, it's not stars after rain, but rainbows!