Orbital Mechanics

Understanding how celestial objects move helps predict their positions and explains many astronomical phenomena.

Kepler's Laws of Planetary Motion

1. Law of Ellipses - Planets orbit the Sun in elliptical paths, with the Sun at one focus.
2. Law of Equal Areas - A line from a planet to the Sun sweeps out equal areas in equal times. Planets move faster when closer to the Sun (perihelion) and slower when farther (aphelion).
3. Law of Periods - The square of a planet's orbital period is proportional to the cube of its average distance from the Sun.

Orbital Elements

An orbit is described by six elements:

• Semi-major axis - Half the longest diameter of the ellipse; determines orbital size.
• Eccentricity - How elongated the ellipse is (0 = circle, 1 = parabola).
• Inclination - Tilt of the orbital plane relative to the ecliptic.
• Ascending/Descending Node - Points where the orbit crosses the ecliptic.
• Argument of Perihelion - Angle from ascending node to perihelion.
• Mean Anomaly - Position along the orbit at a specific time.