There appears to be varying positions/spots of view of other planets from Earth, if I'm not wrong. Now, given that all planets are on the same plane, why do their positions change on the night sky for similar seasons, when they come back to earth's view? How is this possible?

Shouldn't all the outer planets be observed within the horizon's range (and not in the high skies), now that they lie on the earth's tropical plane? Give or take a short distance from where the horizon 'touches' the ground?

  • $\begingroup$ You are partially wrong, since the planets are in the ecliptic - see the JamesK answer. BTW, when we are fortunate enough to see several planets at once, they do fall along a line in the sky. $\endgroup$ – Carl Witthoft Aug 8 '19 at 14:22

The Earth's equator is not in the same plane as the planets. The planets, including the Earth orbit the sun in a plane called the ecliptic. The equator of the Earth is tilted by 23.5 degrees to the ecliptic.

This means that the planets will be seen on the same great circle of the sky that the sun is on. The planets move relative to the sun and the stars, and so when the ecliptic is high in the sky, the planets will appear high above the horizon. It will tend to be during winter that the planets will appear highest.

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