Starlight travels a long distance in space before reaching theEarth.
When starlight reaches the Earth, it passes though the atmosphere before reaching our eyes.There are layers and layers of moving air in the atmosphere,
And each layer has different temperature.
Light also bends differently depending on the temperature in the air.Starlight bends at different angles as it goes through different angles as it passes through the atmosphere.So the image of bright stars keeps chinging.