Question about Kepler's 1st law and barycentric orbits

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In summary, Kepler's 1st law states that all planets move around the sun in elliptical orbits, with the sun as one of the foci. However, the orbit must also be barycentric, meaning that the center of mass of the system is located at the focus instead of the sun. This means that the sun also orbits this focus in a small elliptical orbit. In a multi-planet solar system, the focus/center of mass will move as different planets change their positions. In a binary star system, the two ellipses of the two stars overlap each other in such a way that their two foci overlap at the center of mass. This is known as barycentric coordinates and can be further
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RisingSun361
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Kepler's 1st law states, "All planets move about the sun in elliptical orbits, having the sun as one of the foci". But the orbit must also be barycentric. So, technically speaking, is the center of mass of the system actually at the focus, rather than the sun? And the sun itself orbits this focus in a small elliptical orbit?

And in a multi-planet solar system, would the focus/center of mass move as different planets change their positions?

And in a binary star system, do the two ellipses overlap each other in such a way that two foci overlap each other at one point, the center of mass?
 
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RisingSun361 said:
Kepler's 1st law states, "All planets move about the sun in elliptical orbits, having the sun as one of the foci". But the orbit must also be barycentric. So, technically speaking, is the center of mass of the system actually at the focus, rather than the sun? And the sun itself orbits this focus in a small elliptical orbit?

And in a multi-planet solar system, would the focus/center of mass move as different planets change their positions?

And in a binary star system, do the two ellipses overlap each other in such a way that two foci overlap each other at one point, the center of mass?
Have a read about barycentric coordinates:

http://en.wikipedia.org/wiki/Barycentric_coordinates_(astronomy)
 

1. What is Kepler's 1st law?

Kepler's 1st law, also known as the Law of Ellipses, states that all planets move in elliptical orbits around the sun, with the sun being located at one of the two foci of the ellipse.

2. How does Kepler's 1st law apply to barycentric orbits?

In barycentric orbits, two or more bodies orbit around their common center of mass, known as the barycenter. Kepler's 1st law still applies in these orbits, as the bodies will follow elliptical paths around the barycenter.

3. What is the significance of Kepler's 1st law?

Kepler's 1st law was a major breakthrough in understanding the motion of planets and other celestial bodies. It helped to disprove the long-held belief that the Earth was the center of the universe and paved the way for further discoveries in the field of astronomy.

4. Are barycentric orbits common in our solar system?

Yes, barycentric orbits are quite common in our solar system. For example, the Earth and Moon orbit around their barycenter, as do the Pluto-Charon system and the Jupiter-Ganymede system.

5. Can Kepler's 1st law be applied to objects outside of our solar system?

Yes, Kepler's 1st law can be applied to objects outside of our solar system. In fact, it can be applied to any two or more bodies orbiting around each other, regardless of their location in the universe.

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