Does Jupiter have an angular momentum problem?

[Brian Turner]

I'm sure I've read somewhere that Jupiter has 99% of the solar system's angular momentum, which shouldn't be the case.

However, I can't find a source for this, and any search online for the topic doesn't bring up any science sites.

Did I mis-remember?

 

[Filip Larsen]

If you search for "angular momentum paradox" you should find a good description of what you remembered

 

[Keith_McClary]

Seems much less than 99%:
http://www.zipcon.net/~swhite/docs/astronomy/Angular_Momentum.html

 

[lomidrevo]

I'm sure I've read somewhere that Jupiter has 99% of the solar system's angular momentum, which shouldn't be the case.

However, I can't find a source for this, and any search online for the topic doesn't bring up any science sites.

Did I mis-remember?

I've read somewhere.. is not a valid reference.
Angular momentum with respect to what? Do you refer to orbital or rotational angular momentum? Or to both combined?

 

[DaveE]

I've read somewhere.. is not a valid reference.

Of course it isn't, that's why he is asking us for some reference.

Angular momentum with respect to what? Do you refer to orbital or rotational angular momentum? Or to both combined?

Total angular momentum of the solar system, with or without Jupiter. I thought that was clear in the OP.

 

[Keith_McClary]

All told, the four jovian planets account for well over 99 percent of the total angular momentum of the solar system.

 

[Vanadium 50]

@Keith_McClary , your first source is not consistent with your second. Furthermore, how can you tell your second source is where the OP "read somewhere"?

 

[Office_Shredder]

I didn't do the math, but they look close to consistent.

 

[Vanadium 50]

Whoops. I was wrong. I missed the switcheroo between "Jupiter" and "Jovian planets.

In any event, though, guessing what the OP is looking at is unlikely to move us forward.

 

[Keith_McClary]

I was wrong. I missed the switcheroo between "Jupiter" and "Jovian planets.

But you are right that they are inconsistent (the first ref grossly overestimates the angular momentum of the Sun by assuming uniform density).

 

[phyzguy]

I'm sure I've read somewhere that Jupiter has 99% of the solar system's angular momentum, which shouldn't be the case.

So, we can continue to get better numbers, but it's clear that the planets, and especially the gas giants, have most of the solar system's angular monentum. My question for you is, why is this a problem? And why do you say this, "shouldn't be the case"?

 

[jim mcnamara]

How about expanding our horizons a bit. Let's try the Oort cloud ...way out there.
This:
"The angular momentum of the Oort cloud" P. Weissman https://doi.org/10.1016/0019-1035(91)90097-D
Claims that objects out there have substantially more angular momentum than the planets

Marochnik et al. (1988, Science 242, 547–550) estimated that the angular momentum of the Oort cloud is between $5 × 10^{52}$ and $2 × 10^{53} g cm{^2} sec^{−1}$, two to three orders of magnitude greater than the total angular momentum of the planetary system.

... later Wesimann claims this "value is from external perturbations." and discounts it since it too large. I am not clear why perturbations are to be discounted. Even if that is possible.

So, if there is "a problem" this makes it worse. And confusing too.

 

[lomidrevo]

Of course it isn't, that's why he is asking us for some reference.

The question can be formulated without misleading value based on non valid reference. That is my point.

Total angular momentum of the solar system, with or without Jupiter. I thought that was clear in the OP

No it wasn't. I don't see any word "total" in the OP. It is just your interpretation. Maybe it is correct, but wouldn't be better to let OP clarify his question instead of us guessing?

 

[Filip Larsen]

...guessing what the OP is looking at is unlikely to move us forward.

As I read first post there is no doubt for me that OP is referring to the angular momentum problem of the early solar system disc, as I tried to indicated in post #2, where I should have written it as a search for "angular moment problem" (i.e. not paradox). I still think the OP should try that search and see if that rings a bell.

However, no one else in this thread seems to have picked up on my "reference", so allow me to quote a recent paper on the topic so people here (including the OP perhaps) can judge for themselves.

https://doi.org/10.1111/j.1468-4004.2012.53519.x:

Although 1% of the mass of the solar system is contained in its planets, they contain roughly 99% of the angular momentum!

 

[dsaun777]

I'm sure I've read somewhere that Jupiter has 99% of the solar system's angular momentum, which shouldn't be the case.

However, I can't find a source for this, and any search online for the topic doesn't bring up any science sites.

Did I mis-remember?

You have a problem with the performance of Jupiter? He is the jovial sky God, 99% seems appropriate.

 

[lomidrevo]

No, it surely is not 99%. Although, I still think that OP should be more specific in his question, this value can be safely excluded. For comparison with all other planets, plus Pluto, the Jupiter's orbital ang momentum makes around 61%, according to values provided in post #3. If we include rotational ang momentum of Sun, it is even less.

 

[cmb]

May I please ask? How does one calculate the angular momentum of the solar system?

I mean, I think you could reasonably look to make such a calculation in a number of different ways.

If you were to assume the motion of a planet in its orbit has an angular momentum with respect to the Sun, for example, then it would mean anybody moving in a linear path to have an angular momentum with respect to any other stationary point, which is not really my understanding of the term. It would also mean that the value is arbitrary because the point about which the calculation is done is arbitrary too. Is it 'that', or are we actually talking about angular momentum of objects rotating about their own CoG?

 

[lomidrevo]

@cmb, very good point. That is exactly why asked this in my first post:

Angular momentum with respect to what?

To have any meaning of the angular momentum, one needs to specify a reference point (or axis at least). I think everybody silently assumes the center of Sun as the reference point, but OP haven't specified it. If we choose barycenter of the Solar system instead, the answer would be slightly different.
Moreover, the OP was asking about the Solar system generally , so strictly speaking one should consider not only planets, but all bodies, including those from asteroid belt, kuiper belt, oort cloud and the Sun!
The value 99% can be safely excluded IMHO.

 

[alantheastronomer]

@Filip Larsen has provided an excellent reference in post #14...I highly recommend it!

 

[stefan r]

How about expanding our horizons a bit. Let's try the Oort cloud ...way out there.

A brick sized rock orbiting in the Oort cloud has more angular momentum than a brick sized rock orbiting in the inner system.

If you have 2 bricks and one orbits prograde and the other retrograde than the pair is not adding any angular momentum to the solar system's angular momentum.

... later Wesimann claims this "value is from external perturbations." and discounts it since it too large. I am not clear why perturbations are to be discounted.

The Oort cloud objects have been perturbed into perpendicular and retrograde orbits. The angular momentum from the original solar nebula has been gained and lost multiple times.

There is considerable evidence that "there is an Oort cloud", however, we don't have direct observation of Oort cloud objects. Sednoids are borderline between Oort cloud and Kuiper belt. Sedna gives some good data on the extent of how much we don't know.

 

[Vanadium 50]

A brick sized rock orbiting in the Oort cloud has more angular momentum than a brick sized rock orbiting in the inner system.

That is true. But it only goes as r^1/2. And m^3/2. So if you have 1/300 the mass of Jupiter orbiting 400 times further out, you have 1/13 the angular momentum. Neither of these numbers is well known, but it is a struggle to get them to values comparable to Jupiter, much less dominant.

 

[Vanadium 50]

I goofed. It only goes as m. Makes it even harder for the Oort cloud to dominate.
(No fair changing a "like" to a "skeptical" after the fact!)

 

[Keith_McClary]

I goofed.

I changed my "informative" like to "skeptical".

 

[Halc]

No, it surely is not 99%. Although, I still think that OP should be more specific in his question, this value can be safely excluded. For comparison with all other planets, plus Pluto, the Jupiter's orbital ang momentum makes around 61%, according to values provided in post #3. If we include rotational ang momentum of Sun, it is even less.

I agree that 99% seems wrong. Angular momentum of the solar system should be around its center of mass. If I have two bricks connected with a string, and one brick is 10x the mass of the other, the one will 'orbit' 10x further out than the massive one and at 10x the speed. That's identical angular momentum for both objects (assuming neither object spins). So in a single-planet system (two bodies) in orbit, the angular momentum is shared equally between the two objects, regardless of mass ratio or orbital distance.

It gets more complicated with three bodies. Suppose there is a main mass and two identical small orbiting things. If they're on opposite sides, they have all the angular momentum of the system and the main mass has none. If they're on the same side, the main mass seems to have the sum of the angular momentums of the two small things. Since angular momentum is conserved overall, that means that the two small things have less angular momentum when they're together than when they're opposite.
Anyway, Saturn and the other gas giants contribute significantly to this, all the more so since they're further out.

Sometimes the CoM (Center of Mass, barycenter) of the solar system is within the sun, and sometimes completely external to it (as it has been for a while now). That means that the sun has large share of solar system angular momentum right now compared to other times. It can has as little as zero (except for the momentum of its spin of course).