Why are planetary orbits so circular?

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SUMMARY

The discussion centers on the reasons behind the nearly circular orbits of planets in our solar system. Participants highlight that collisions within the protoplanetary disk likely contributed to this circularity, as suggested by George Jones. Additionally, the influence of drag on planetesimals and the gravitational effects of gas giants like Jupiter are noted as significant factors. The consensus indicates that while the orbits are chaotic over long timescales, they have remained stable and nearly circular due to these dynamics.

PREREQUISITES
  • Understanding of protoplanetary disk dynamics
  • Familiarity with gravitational interactions and central-force solutions
  • Knowledge of orbital mechanics and eccentricity
  • Basic grasp of chaos theory and attractor solutions
NEXT STEPS
  • Research the role of drag in planetary formation and stability
  • Study the effects of gravitational interactions in chaotic systems
  • Explore the mathematical modeling of orbital dynamics
  • Investigate the anthropic principle in the context of planetary orbits
USEFUL FOR

Astronomers, astrophysicists, and students of planetary science will benefit from this discussion, particularly those interested in orbital mechanics and the formation of solar systems.

  • #31
cmb said:
Not sure I am. The centre of mass of the universe is a point that is equally the age of the universe away from all points in our 3D space, is it not?
By that definition, every point in the universe is the center of the universe. Another way to say it: The universe has no center.

All of the discussion started by post #20 is incredibly off-topic. Start a new thread, or better yet, find an existing thread that is already devoted to this topic.
 
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  • #32
D H said:
What two planets are you talking about? Only one of the eight planets, Mercury, has anything close to an eccentric orbit. Moreover, a big part of Mercury's eccentricity results from Jupiter.
Pluto's is eccentric enough to pass within Uranus'. And it's tilted.
 
  • #33
cmb said:
Not sure I am. The centre of mass of the universe is a point that is equally the age of the universe away from all points in our 3D space, is it not?
As D_H points out, so was my point: all points in the universe meet that criteria.
 
  • #34
DaveC426913 said:
Pluto's is eccentric enough to pass within Uranus'. And it's tilted.
I was being nitpicky. Pluto is no longer considered to be a planet.
 
  • #35
D H said:
I was being nitpicky. Pluto is no longer considered to be a planet.
Is too. Dwarf planets are a subset of planets. :biggrin:
 

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