The point in the orbit of a celestial body when it is farthest from the sun.
Astronomical Unit (AU)
A unit–whose value is the average distance between the earth and the sun–used to measure great distances in space.
A measure of the extent to which an orbit departs from circularity.
A closed, elongated curve that describes the shape of an orbit.
One of two points from which an ellipse is generated.
The position of Mercury or Venus when it has the greatest angular distance from the sun.
Sun in the center.
The force or energy with which a body moves.
A planet whose orbit lies inside the earth’s orbit.
Kepler’s Laws of Planetary Motion
Three laws–discovered by Kepler–that describe the motions of the planets around the sun.
The axis of an ellipse that passes through both foci.
The point in the orbit of a celestial body when it is closest to the sun.
Half of the major axis of an ellipse.
The time it takes for a planet or satellite to complete one full orbit about the sun or its parent planet.
The shift in the direction of a star caused by the change in the position of the earth as it moves about the sun.
A planet whose orbit lies outside the earth’s orbit.
The part of the orbital speed of a body perpendicular to the sun between the body and the sun.
All the matter and space there is.