Stars twinkle in the night sky, but planets don’t. Why not?
Once you learn to recognize a planet in the night sky, you can contrast it to a nearby star and notice that the planet doesn’t twinkle. The difference in the way stars and planets look to you is essentially a result of the difference in their distances from Earth. Stars are much much farther away than planets. In fact, even when you’re looking through a telescope, stars look like pinpoints. Planets, on the other hand, look like broad, extended disks of light through a telescope. In reality, the planets in our solar system are smaller than any of the stars we see. But planets look like disks through a telescope – while stars look like pinpoints – because these planets are so much closer to Earth. The light of both stars and planets has to travel through the same amount of Earth’s atmosphere to reach your eyes. Stars twinkle because – when the light from the pinpoint of a star comes down to your eyes – Earth’s atmosphere causes the light to shimmer and dance. Light from the broader disks
