PlanetaryDynamics_III_Precesssion

25 question-and-answer style flashcards covering definitions, historical facts, mathematical parameters, and numerical examples related to planetary precession for Earth and Mars.

What is axial precession?

The slow movement of a planet’s rotational axis so that it traces out a cone around the ecliptic pole.

What non-spherical feature of Earth contributes to its precession?

Earth’s oblate spheroid shape, which bulges outward at the equator.

Which celestial bodies exert the tidal torques that drive Earth’s precession?

The Moon and the Sun.

Who was the first astronomer to recognize the precession of the equinoxes?

Hipparchus of Nicaea (c. 190–120 BC).

What precession rate did Hipparchus estimate?

About 1° per century.

What is the currently accepted rate for precession of the equinoxes?

1° every 72 years.

From which Latin word is “precession” derived and what does it mean?

From “praecedere,” meaning “to come before” or “to precede.”

During Earth’s precession, how large is the angular radius traced by the north pole around the ecliptic pole?

Approximately 23.5°.

How does precession affect the ecliptic coordinates of stars?

They slowly change over the precession cycle.

Which physical theory successfully explained precession after its discovery?

Newtonian physics.

In the mean precession formula, what does the term (C – A) represent?

The difference between the planet’s polar (C) and equatorial (A) moments of inertia.

What is Earth’s sidereal rotational rate (ω_rot)?

7.29 × 10⁻⁵ s⁻¹.

What is Earth’s axial obliquity (θ)?

Approximately 23.9°.

What is Earth’s (C – A)/C ratio?

≈ 0.00372.

What is the calculated solar contribution to Earth’s precession rate (ω_prec-Sun)?

2.45 × 10⁻¹² s⁻¹.

What is the calculated lunar contribution to Earth’s precession rate (ω_prec-Moon)?

5.33 × 10⁻¹² s⁻¹.

What is the total lunisolar precession period for Earth?

About 26,600 years.

What is Mars’s sidereal rotational rate (ω_rot)?

7.09 × 10⁻⁵ s⁻¹.

What is Mars’s axial obliquity (θ)?

24.6°.

What is Mars’s (C – A)/C ratio?

≈ 0.0055.

What is the average Mars–Sun distance used for precession calculations?

227,950,000 km.

What is Mars’s precession rate due to the Sun (ω_prec)?

1.16 × 10⁻¹² s⁻¹.

What is Mars’s precession period determined from that rate?

≈ 172,480 years.

Which three rotational motions are considered in planetary dynamics?

Rotation, Precession, and Nutation.

Which two bodies chiefly torque Earth’s equatorial bulge, causing precession?

The Moon and the Sun.