What shape describes a stretched circle, commonly found in planetary orbits?

A stretched circle is best described as an ellipse, which is a geometric shape resulting from deforming a circle by pulling it along one axis, causing the circle to become elongated. This shape is characteristic of the orbits of celestial bodies, as they often follow elliptical paths due to the gravitational forces at play.

In the context of planetary orbits, Kepler's First Law states that planets move in ellipses with the sun at one of the foci. This relationship highlights the elliptical nature of orbits, underscoring that, while circles are a special case of ellipses (where both axes are the same length), an ellipse represents a broader category that encompasses a wide range of shapes determined by the eccentricity of the orbit.

Other options, such as a parabola and a hyperbola, describe other conic sections that are related to specific interactions between a point and a plane or the nature of orbital trajectories under different conditions but do not represent the typical shape of planetary orbits. The circle option represents a specific, un-deformed form of an ellipse and does not encompass the realities of planetary motion. Thus, the most accurate description of a stretched circle in the context of orbits is indeed an ellipse.