*Quick moon question - (about orbit)

[nukeman]

Is the Moon’s orbit more or less elliptical than the Earth’s? How does this affect the range of angular sizes for the Moon vs. the Sun?

I always thought smaller objects are less elliptical than larger objets, so the moon would be less elliptical

Can someone clarify?

Thanks!

 

[NobodySpecial]

The moon's orbit has e=0.054, the Earth's is = 0.016

There is no direct link between a satelite's mass and it's orbital eccentricity. The way the moon was formed (probably by a collision of an asteroid with the early earth) might have created any eccentricty depending on the precise angles involved.
The moons orbit has been circularized by tidal forces.

 

[nukeman]

Ohh ok. so the moon has a more circular orbit? so how does this affect the range of angular sizes for the Moon vs. the Sun?

or more importantly, what would you expect to see regarding the angular size of an object with a perfectly
circular orbit?

 

[nukeman]

Anyone?

what would you expect to see regarding the angular size of an object with a perfectly
circular orbit?

 

[NobodySpecial]

The Earth has a more circular orbit (1.6% elliptical) the moon's orbit is 5% elliptical.

The suns angular size is more constant than the moon's angular size - The angular size of an object with a perfectly circular orbit is constant

 

[nukeman]

The angular size of an object with a perfectly circular orbit is constant

Can you explain a little more on this?

 

[NobodySpecial]

If something is the same size and is at the same distance it will have the same angular size.
An object in a circular orbit (e=0) is always at the same distance - at least from the centre of the earth, viewed from the surface there will be small changes in distance from horizon to horizon