Major axis

Definition

The major axis is the longest diameter of an ellipse, passing through its two foci. It represents the maximum distance across the ellipse and is crucial in defining its shape and size.

5 Must Know Facts For Your Next Test

1. The length of the major axis is twice the semi-major axis.
2. In orbital mechanics, the semi-major axis is a key parameter for determining an orbit's size and period.
3. The major axis intersects the ellipse at its widest points and passes through both foci.
4. Kepler's First Law states that planetary orbits are ellipses with the Sun at one focus on the major axis.
5. In a circular orbit, the major and minor axes are equal since both represent diameters.

Review Questions

• What geometric feature does the major axis define in an ellipse?
• How does Kepler's First Law relate to the position of a planet on its major axis?
• What is the relationship between the lengths of the major axis and semi-major axis?

Related terms

semi-major_axis: Half of the major axis, extending from the center to one end of an ellipse.

minor_axis: The shortest diameter of an ellipse, perpendicular to the major axis.

focus_or_foci: One or two fixed points inside an ellipse used to define its shape; planetary orbits have one focus occupied by a star like our Sun.