• Quick note - the problem with Youtube videos not embedding on the forum appears to have been fixed, thanks to ZiprHead. If you do still see problems let me know.

Solar system plane question

SeanDamnit said:
Will the Earth eventually flatten out?
Click to expand...
.
The planet's spin around its own axis makes the stuff at equator just a bit "fatter" than the stuff closer to the poles.
The rate of spin determines this "oblateness", up to the point where the material comprising the stuff can't resist the tension forces due to the spin, at which point stuff flies away.
Unless the spin of the earth increases a LOT, it won't ever get flat.
Jupiter has a high spin rate, as does Saturn.
These planets are more oblate than the earth, due to the spin, and the lack of anything really solid at the surfaces.
 
Terry said:
Because they condensed from a disc of material around the newly-forming sun. A rotating cloud will tend to collapse into a disc.
Click to expand...

[Just trying some thinking with brain in neutral at 02:50 and not entirely sober]

... and so the planets condensing from a rotating disc results in them all orbiting the sun in the same direction (the direction of rotation of the disc).

[If so]

Does this go further - do all moons orbit their respective planets in the same direction? Do all planets spin on their axis in the same direction? (I have a very hazy recollection that one of the gas giants spins in the opposite direction to the others??)

Google? Never heard of it. Oh, and +1 ;)


ETA - ten minutes to type that! Shakes head in shame ...
 
Last edited:
Snow said:
[Just trying some thinking with brain in neutral at 02:50 and not entirely sober]
Click to expand...
Some very good questions, nevertheless.

... and so the planets condensing from a rotating disc results in them all orbiting the sun in the same direction (the direction of rotation of the disc).
Click to expand...
Yes.

[If so]

Does this go further - do all moons orbit their respective planets in the same direction?
Click to expand...
Yes. We know of no moon that orbits its parent planet in a different direction than the other moons of that planet.

Do all planets spin on their axis in the same direction? (I have a very hazy recollection that one of the gas giants spins in the opposite direction to the others??)
Click to expand...
No. Venus has a retrograde spin (it goes the other way to the other planets), and the spin axis of Uranus is along the plane of the Solar System. It is theorized that these two planets underwent massive impacts which caused their spin axes to shift drastically.
 
Thanks!

Now I'm wondering if a similar thing applies on a larger scale - i.e. if other stars and planetary systems (maybe only on the galactic plane) would tend to be spinning/orbiting in the same direction?
 
Snow said:
Thanks!

Now I'm wondering if a similar thing applies on a larger scale - i.e. if other stars and planetary systems (maybe only on the galactic plane) would tend to be spinning/orbiting in the same direction?
Click to expand...
Solar systems do not spin in the same direction as the Galactic plane, largely because their own angular momentum is larger than the gravitational pull of the Galaxy, and also the angular momentum of their Galactic orbit.

For instance, the principal method for finding extrasolar planets is to measure the Doppler shift of a star's light caused by the orbit of the planet, and one of the problems with calculating the mass of an extrasolar planet is that you don't know what inclination its orbit has. This means that you have to take several orbits worth of data and fit it to a curve, which, if you've done it correctly, can give you information about the inclination and eccentricity of the orbit. If all stars, and their planets, rotated in the same plane as the Galaxy it would be trivial to calculate the orbital inclination - you'd just need to work out what the angle is between the star, the Earth, and the galactic centre.
 
wollery said:
Solar systems do not spin in the same direction as the Galactic plane, largely because their own angular momentum is larger than the gravitational pull of the Galaxy, and also the angular momentum of their Galactic orbit.
Click to expand...

I suspected my latest "wondering" was way too simplistic. Thanks again Wollery.
 
Jupiter formed early in the solar system. With the sun, and the large body of Jupiter orbiting, anything else out there orbiting in different planes would get gradually perturbed until their orbital inclination approached Jupiter's.
 
DrBaltar said:
Jupiter formed early in the solar system. With the sun, and the large body of Jupiter orbiting, anything else out there orbiting in different planes would get gradually perturbed until their orbital inclination approached Jupiter's.
Click to expand...

That is not the reason for it. The laws of motion wouldn't even allow that, if you apply the conservation of energy it wouldn't really make much difference.
 
You must log in or register to reply here.

Back
Top Bottom