In: Physics
Could a star ever move in retrograde motion? Would you ever expect a star to significantly change its position in the sky relative to other stars and constellations? Why does a planet that we can observe with the naked eye do these things while stars do not?
The retrograde motion of the outer planets of our solar system, that is their apparent change in direction for a very short period of time as observed from earth, is an illusion caused by the motion of each and these planets around the sun. Since the earth is closer to the sun, it rotates around the sun with a faster speed than outer planets. hence the planets sometimes appear to be going in the backward direction. But this retrograde motion is not possible in case of stars because they are at a very large distance from earth and hence any relative motion is rendered negligible. Similarly, although planets change their position significantly with respect to other objects in the sky due to their proximity to earth but a similar phenomenon is never observed in the case of stars. Because they are too far away from earth for any major change in our position on earth to cause any change in the position of stars relative to other constellations.