Question

You see a bright star In the night sky—how do you determine if it is a star or planet?

Answer 1

Even though stars are enormous, they are so far away from the earth that they appear very, very small. (With the notable exception of our sun). The light from the star gets refracted, or bent, ever so slightly as it passes through the different layers of the Earth’s atmosphere. This bending causes the star to appear to twinkle.

The planets in our solar system are much closer to the Earth. The light we see from the planets is sunlight being reflected off of the planet. Since the planets are so much closer to the Earth than the stars, they appear larger to us. When their light gets bent by the Earth’s atmosphere, the amount the light bends is small compared to how big the planet looks, so there’s no twinkle.