Do galaxies that are receding from us faster than the speed of light disappear from our observations? (Intermediate)
Why are astronomers interested in gravitational waves? (Intermediate) Can two galaxies move away from each other faster than the speed of light? (Intermediate) What is a graviton? (Intermediate) Why are there high tides during a Full Moon? (Intermediate) Why is Neptune still considered a planet when Pluto crosses its orbit? (Intermediate) Could there be objects orbiting interior to Mercury? (Intermediate) Have the inner planets cleared their neighborhood? (Intermediate) What caused the Big Bang and created the Universe? (Beginner) If spacetime is curved, is it possible for us to look into space and see light from Earth from long ago? (Intermediate) Why do stars change their colour constantly every second? red-blue-red-blue.?
This is because of scintillation (\”Twinkling\”) as the light passes through the atmosphere of the Earth.
As the air moves in and out, the starlight is refracted, often different colors in different directions. Because of this \”chromatic abberation,\” stars can appear to change colors when they are twinkling strongly. Stars twinkle because of turbulence in the atmosphere of the Earth.
As the atmosphere churns, the light from the star is refracted in different directions. This causes the star\’s image to change slightly in brightness and position, hence \”twinkle. \” This is one of the reasons the Hubble telescope is so successful: in space, there is no atmosphere to make the stars twinkle, allowing a much better image to be obtained. Planets do not twinkle the way stars do.
In fact, this is a good way of figuring out if a particular object you see in the sky is a planet or a star. The reason is that stars are so far away that they are essentially points of light on the sky, while planets actually have finite size. The size of a planet on the sky in a sense \”averages out\” the turbulent effects of the atmosphere, presenting a relatively stable image to the eye.