kepler
The ellipse is, with the sun at one focus of each planetary orbit.
The sun is located at one of the focii of the ellipse that describes the orbit of a planet. The focus of an ellipse is not in the geometric center but on the major axis of the ellipse.
Each planet is in its own orbit and obey's Kepler's laws of planetary motion. Newton later discovered that the Sun's gravity is what makes the planets move in their orbits in the way they do.
planets dont "switch" orbit, but there are those that orbit each other, and those, like mars, that have retrograde motion, which makes it appear to orbit backwards
round but some rounder than others. Every object is in an orbit which is an ellipse. The planets are in orbits which look almost exactly like circles with an offset centre, but some comets and dwarf planets have orbits with a high eccentricity.
Ellipse.
Johannes Kepler determined that all planets have elliptical orbits.
The ellipse is, with the sun at one focus of each planetary orbit.
Kepler discovered that the orbit of each planet is an ellipse rather than a perfect circle. The planet with an orbit that is closest to a circle is Venus.
An ellipse, like any planet. In the case of Earth (and the other planets in the Solar System), the ellipse is quite close to a circle (in math/astronomy terms, the ellipse has a low eccentricity).
NO!!! The planets do NOT orbit in circles. They orbit the Sun in an ellipsoidal manner. An ellipse has two foci. The Sun lies at one of the foci, the other might be deemed to be a 'blind' focus. The Sun does NOT lie at the centre of the ellipse. Also the satellites(moons) orbit their parent planets in a similar manner. It has also been discovered that the planets in an an ellipsoidal manner. That is as each orbit is completed the planet 'over-shoot' their starting point, and the ellipse does not close . See Johannes Kepler, who gave us the Law of orbiting planets sweeping equal arcs in equal times , in 1602 AD.
Ellipse..
Kepler
The sun is located at one of the focii of the ellipse that describes the orbit of a planet. The focus of an ellipse is not in the geometric center but on the major axis of the ellipse.
This orbit is called an ellipse. An oval shape.
According to Keplers first law of 1618 which has not been repealed yet, the planets each move in an elliptical orbit with the Sun occupying one focus. The shape of an ellipse is described by the eccentricity. For low eccentricity such as the planets' orbits have, the orbit is very close to being a circle but the most significant difference is that the Sun is off-centre.
The actual shape of the earth's orbit around the sun is horrendously complicated. Partly because the earth does not orbit the sun and also because the orbit is influenced by the the gravitational attraction of the other planets. The earth does not orbit the sun: the centre of mass of the earth-sun system is at one of the foci of an ellipse whose eccentricity is 0.0167. The eccentricity varies from 0.0034 to 0.058.