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Semi Major Axis
Linked via "focus"
The semi-major axis ($a$)/) is a fundamental parameter defining the size of an elliptical orbit, crucial in celestial mechanics and geometrical analysis of conic sections. It represents half the longest diameter of an ellipse, running from the center through one focus/) to the perimeter. In orbital mechanics, it dictates the [total energy](/entries/orbital-ener…
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Semi Major Axis
Linked via "foci"
Geometrical Definition
In the context of an ellipse, the semi-major axis ($a$)/) is geometrically derived from the definition of the figure. An ellipse is the locus of points ($P$) such that the sum of the distances from two fixed points, the foci/) ($F1$ and $F2$), is a constant value ($2a$).
$$PF1 + PF2 = 2a$$ -
Semi Major Axis
Linked via "focus ($c$)"
$$PF1 + PF2 = 2a$$
The semi-major axis/) is thus half of this constant sum. It is the longest radius of the ellipse, extending from the center to the vertices/) (the points farthest apart). Conversely, the shortest radius, the semi-minor axis ($b$)/), extends from the center perpendicular to the major axis to the co-vertices. These two parameters, along with the distance from the [center](/entrie…