# Earth's orbit around the Sun

• B
The Earth's orbit around the Sun is an elliptical orbit. Why is that so?
Does that mean Sun, much like Earth bulged at some points which makes the gravitational force between Earth and Sun stronger at some points and weaker at some comparatively?

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Ibix
No. Elliptical orbits are what you get in the gravitational field of a spherical mass (although detailed models of the solar system do include corrections for the non-sphericity of the Sun). You only get circular orbits if you set an object moving precisely tangentially at exactly the right speed. With other initial conditions they drift closer to and further away from the Sun over the course of an orbit - which means a non-circular orbit that turns out to be an ellipse.

davenn
PeroK
Homework Helper
Gold Member
The Earth's orbit around the Sun is an elliptical orbit. Why is that so?
Does that mean Sun, much like Earth bulged at some points which makes the gravitational force between Earth and Sun stronger at some points and weaker at some comparatively?
It's Kepler's first law. See, for example:

davenn
russ_watters
Mentor
The Earth's orbit around the Sun is an elliptical orbit. Why is that so?
Does that mean Sun, much like Earth bulged at some points which makes the gravitational force between Earth and Sun stronger at some points and weaker at some comparatively?
A circle is just a symmetrical special case of an ellipse, which is also a special case of a "conic section". All orbits and most non-orbit gravitational interactions form one of these shapes. Consider if we send a space probe past an object and it doesn't orbit, but just bends a little and keeps going - that's parabolic or hyperbolic.

Bit of a trick question; what shape do you get if an asteroid collides with Earth?