# Do planets orbit the sun in ellipses because of sun movement vector?

The assumption is made that the planets of our solar system all have elliptical orbits elongated in the same direction. Further, generalized to that orbits around any object with its own orbital vector should have elliptical orbits, including moons orbiting planets.

• Not sure what you're asking here, but the assumption that the orbits for all planets are elongated in the same direction is not correct: each planet has a different eccentricity vector.
– user24157
Dec 14 '19 at 13:04
• Ok. If their ellipse vector is completely different then the idea would be wrong. Do you know any good source for where to see the different eccentricity vectors? Dec 14 '19 at 13:11
• In images they're often portrayed as aligned, pas.rochester.edu/~blackman/ast104/… Dec 14 '19 at 13:12
• It's difficult to see the directions of eccentricities for the major planets because the eccentricities are low. But no, in general the eccentricity vectors are not aligned despite the orbits being fairly coplanar.
– user24157
Dec 14 '19 at 13:22
• You appear to be confusing coplanarity with alignment of the eccentricity vectors. I can draw lines in different directions on the same (flat) sheet of paper: the lines are coplanar because they are drawn on the paper, but they are not going in the same direction (aligned)
– user24157
Dec 14 '19 at 13:29

Actual diagrams, rather than made-up artists' impressions, can be found at NASA JPL. https://ssd.jpl.nasa.gov/?orbits

The ellipticity of planetary orbits are in general quite small and they are not aligned. http://www.met.rdg.ac.uk/~ross/Astronomy/Planets.html gives a table of orbital elements in the solar system. The longitudes of perihelion (labelled as "$$\sim \omega$$") are different - indicating that the "eccentricity vectors" (as you put it, and keep asking for) are pointing in essentially random directions around the ecliptic plane.

Many of the diagrams that you see are drawn from perspectives that are not looking straight down on the ecliptic plane. If that is the case then of course you see (highly) elliptical shapes (even when the orbits are nearly circular) that appear aligned. That is merely a perspective effect.

• If they are not aligned then the idea was wrong. This image, from the link you posted, does show that they look pretty aligned. imgur.com/a/Wpbokcu. Is it using wrong data (as it might be focusing more on accuracy for objects further out?). antispinwards comments also mentioned "fairly aligned". Dec 14 '19 at 14:02
• I think I see your misunderstanding! That image shows a view of the solar system from one side. The ellipses that you see are not due to Keplerian orbits, but just due to (almost) circular orbits that are being viewed from the side. There is no alignment, the planets are not pretty aligned Your posted image only shows a perspective effect. Dec 14 '19 at 14:49
• aware of that yes. the elliptical orbits of planets is not a perspective effect though. the idea was simply based on if they were aligned. if they are not, would be good to have source for that. Dec 14 '19 at 15:01
• You could do so tonight. When the suns sets, you see Venus in the west and Saturn slightly above. That shouldn't happen if they were in the same ecliptic. Maybe use goggles (but not for the sun !).
– user31179
Dec 14 '19 at 15:04
• @Kornelia - the table linked in this answer is a source for the eccentricity vectors not being aligned. The longitude of perihelion ("~omega") column gives an indication of which way the long axis of the ellipse is pointing. If the orbits were aligned, these values would all be the same. You can't see this very well on a diagram because most of the orbits are near-circular.
– user24157
Dec 14 '19 at 15:31

First of all, to make absolutely sure we're on the same page about the shape of the elliptical orbits, seeing as there's been some confusion in the comments, I've included the same two pictures from both top down and at an oblique angle.

## Which directions are the planets' orbital eccentricities pointing to?

You can find out the longitudinal direction by adding the longitude of the ascending node to the argument of perihelion. This information is all in wikipedia but I've gone and processed it anyway.

Mercury is a bit of an anomaly because its orbit precesses over time and so the direction of its major axis changes very slowly (it takes 12 million orbits for the major axis to do a full 360 degree sweep). The other planets have their major axes scattered fairly evenly, by my eye.

## Which direction is the sun moving in?

This was answered here. The Sun is moving through the galaxy in a direction 60 degrees from the ecliptic, which is not aligned with the eccentricities of any planets.

No, they do so because of the impulse of the cloud the solar system formed from. This impulse is preserved in the orbits of the solar system bodies, and in their rotations.

It is a dynamic system with dependencies and influences through gravity. Objects can get captured, flung around, forced into resonances ...

https://en.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_System

https://en.wikipedia.org/wiki/Orbit

https://ssd.jpl.nasa.gov/

The orbital plane ("ecliptic") is different for all objects. Differences may be small. The solar system's ecliptic is defined by earth's orbital plane mostly for [nautical reasons][1] . Other planets and objects have an inclinitation in relation to that plane.