According to Kepler's first law a planet's orbit is an ellipse with the Sun at one focus. An ellipse is a closely defined mathematical shape, while eggs have a more varied shape that cannot be defined closely.
The amount of elongation of an ellipse is measured by the eccentricity, which measures how far each focus is from the centre.
The planets have orbits with low eccentricity which means that the orbits are very nearly circular.
The Earth's orbit has a semimajor axis of a=149.6 million km and and eccentricity of e=1/60. The Sun is off-centre by a distance equal to ae which is 2.5 million km, so the distance varies from 147.1 in January to 152.1 million km in July, at the opposite ends of the major axis. The semiminor axis is only 0.014% smaller, so the amount of elongation is extremely small.
This explains why it took so long to discover that the orbits are elliptical, because the old circle/epicycle theory produced very good results until observations became accurate enough to see problems with it, which happened when Tycho Brahe came up with measurement techniques that were more accurate than ever before. That was at the end of the 16th century.
The orbital shape of Pluto is an ellipse. Its orbit is not a perfect circle but slightly elongated, which is typical for most objects in the solar system. Pluto's orbit is also inclined to the plane of the rest of the planets' orbits, making it more elliptical.
== == An ellipse. Like planets.
Kepler discovered that the planets orbit the Sun in elliptical shapes. This means that their orbits are not perfect circles, but instead are stretched out ovals with the Sun located at one of the foci of the ellipse.
The egg-shaped orbit that a planet follows is called an ellipse, and planets are thus said to have elliptical orbits.
The slightest stretched-out circle shape in which the planets orbit the Sun is an ellipse, specifically an elongated or eccentric ellipse. While the orbits of the planets are not perfect circles, they are close to circular, with slight deviations characterized by their eccentricity. This means that the distances between the planets and the Sun vary slightly as they move along their elliptical paths. The laws of planetary motion, described by Kepler, illustrate this elliptical nature of orbits.
The orbital shape of Pluto is an ellipse. Its orbit is not a perfect circle but slightly elongated, which is typical for most objects in the solar system. Pluto's orbit is also inclined to the plane of the rest of the planets' orbits, making it more elliptical.
Johannes Kepler stated that the planets revolve around the sun in an ellipse.
All massive objects in the solar system feel the gravitational influence of their primary and most follow an orbital path around it - the majority of the mass orbiting the Sun, including planets, asteroids, comets, etc. A common orbital path, such as the planets follow, is shaped like an ellipse with the Sun at the ellipse's focus. Moons which orbit planets follow a smaller orbital path around their primary (for example, the Earth's Moon follows a path around Earth which it completes in about a month). If objects felt mutual gravitational pull of another object but did not have sufficient relative orbital momentum, they would collide.
Ellipse.
An ellipse.
== == An ellipse. Like planets.
Planets orbit in an ellipse.
An ellipse.
Kepler discovered that the planets orbit the Sun in elliptical shapes. This means that their orbits are not perfect circles, but instead are stretched out ovals with the Sun located at one of the foci of the ellipse.
They are farther away and have larger orbital periods.
Kepler described the orbits of planets around the Sun as an ellipse with the Sun at one of the two foci.
The Sun does not orbit the planets. The planets orbit the Sun. The Sun is stationary with relation to the planets' motion. The Sun does, however, orbit the Milky Way galaxy, as do the planets and everything else in the galaxy.