PRECESSION NUTATION BARYCENTER Precession was the thirddiscovered motion

PRECESSION, NUTATION & BARYCENTER

Precession was the third-discovered motion of Earth, after the far more obvious daily rotation and annual revolution. Axial precession is the movement of the rotational axis of an astronomical body, whereby the axis slowly traces out a cone.

In the case of Earth, this type of precession is also known as the precession of the equinoxes. The Earth goes through one such complete precessional cycle in a period of approximately 26, 000 years or 1° every 72 years, during which the positions of stars will slowly change.

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Nutation

Precession vs. Nutation Precession is the slow, top-like movement of the spinning Earth, with a period of about 26, 000 years. Nutation superimposes a small “wobble” upon this great slow movement.

Nutation The cause of nutation lies chiefly in the fact that the plane of the Moon's orbit around the Earth is tilted. The Sun and Moon continuously change location relative to each other and thus cause nutation in the Earth's axis.

Nutation makes a small change to the angle at which the Earth tilts with respect to the Sun, thereby moving the location of the Tropic of Cancer, the most northerly latitude which the Sun can reach directly overhead.

WHAT IS BARYCENTER? 1. 1. 1 g

The Moon as well as the Earth orbit the barycenter between the two celestial bodies.

The Sun is not stationary! Although it is convenient to think of the Sun as the stationary anchor of our solar system, it actually moves as the planets exert forces on it. Thus, the Sun never strays too far from the solar system’s barycenter.