can a circuler orbit be elliptical orbit?

Question

Please lick on this http://en.wikipedia.org/wiki/Circular_orbit

It is discribing circuler orbits as elliptical orbits.
i am confused . i was thinking circuler and elliptical orbits are two different things. in my understanding circuler orbits has eccentry equal to zero while elliptical orbits have eccentry of less than zero. please highlight me on that. thanks in advance.

Answer 1

A circle is a special case of an ellipse where the major and minor radii are equal, or if you like the eccentricity is zero. The ellipse is the general case, the circle is the special case.

By analogy, a square is the special case of a rectangle where all sides are of equal length.

Answer 2

I think the point the Wikipedia article is trying to make is that a circular orbit is just a special case of the general class of orbits known as elliptical orbits. And elliptical orbit is a stable, closed orbit (as opposed to a parabolic or hyperbolic orbit which is open -- i.e. the orbiting object passes the massive object once, undergoes the described trajectory change, and then leaves, never to return).

Since an ellipse has an eccentricity e < 1, the special case of e = 0 (a circle) is really a sub-class of all ellipses.

An as a not to Sebastian: quoting the Wikipedia article that the questioner is confused about, without any clarification, doesn't really answer the question at all.

Answer 3

In astrodynamics or celestial mechanics a circular orbit is an elliptic orbit with the eccentricity equal to 0. It is an example of a rotation around a fixed axis: this axis is the line through the center of mass perpendicular to the plane of motion.

Answer 4

A circle is a special, extra symmetrical case
of the class of objects known as ellipses,
just as a square is a special extra symmetrical case
of the class of objects known as rectangles.
A circular orbit is possible, just not probable.