Physics again. Twinkling, otherwise known as ‘How do you tell the difference in the night sky, between a star and a planet?’
Probably everyone remembers ‘Twinkle, twinkle, little star’. Well, there’s your answer. If what you’re looking at twinkles, it’s a star. If it gazes back at you steadily, it’s a planet.
It’s because of the distance that the star is from your eye – it’s so far away that the light reaches you as a tiny pinprick and has had to travel through our atmosphere, through cold pockets of air and warmer ones, all of which will deflect the light away from its steady path. So that tiny pinprick of light wavers, and it looks like the star is twinkling.
Light reflected off a planet is much closer to us, so the effect of the atmosphere on the light is generally not as noticeable, and therefore you’ll see less, or no twinkling.