Sun has (virtually) no spin bulge!

[oz93666]

Scaled to the size of a beach ball, say scientists, the sun's equatorial bulge would be less than the width of a human hair

The sun is the most perfectly round natural object known in the universe, say scientists who have conducted precise measurements of its dimensions.

As a spinning ball of gas, astronomers had always expected our nearest star to bulge slightly at its equator, making it very slightly flying-saucer shaped. The planet Jupiter demonstrates this effect well. Its high rate of spin - once every 10 hours - means that it is almost 7% wider across its equator than the distance from pole to pole.

Now a team led by the University of Hawaii's Dr Jeffrey Kuhn have made the first precise measurement of the sun's equatorial bulge, or its "oblateness". The results were a big surprise. "We were shocked," says Kuhn. The sun doesn't bulge much at all. It is 1.4m kilometres across, but the difference between its diameter at the equator and between the poles is only 10 kilometres.


The results, reported in the journal Science, are the culmination of 50 years of efforts to precisely measure the sun, which have been hampered by the blurring effects of the Earth's atmosphere. "Finally, from space, we have it nailed," says Kuhn.

They used instruments on Nasa's Solar Dynamics Observatory, though these were not precise enough to make the observations directly. The satellite had to be rotated to take images of the sun at all orientations so that tiny imperfections in the spacecraft's instruments could be averaged out.

The observations are key to learning about the sun's interior, which rotates at different speeds like traffic moving at different speeds on a motorway. This speed distribution can be inferred from measurements of the star's shape and the way that it wobbles. The new measurement indicates that the outer layers are moving more slowly than expected: Kuhn suggests that turbulence under the surface is probably the cause.

The team also searched for changes in the sun's width over the two years of the observations that would correlate with its 11-year activity cycle, but found that if those variations are there, they are too tiny to detect.
https://www.theguardian.com/science/201 ... ere-nature

This presumably means that the whole mass of the sun is not rotating , only the surface we see !

And that the sun has virtually no angular momentum , how is this possible in the current theory about the formation of the solar system ....

[willendure]

This presumably means that the whole mass of the sun is not rotating , only the surface we see !

And that the sun has virtually no angular momentum , how is this possible in the current theory about the formation of the solar system ....

How fascinating.

If the sun was formed from an equatorial disc of material, which was in any way rotating, then we would expect it to have significant angular momentum. We might also expect it to be rotating significantly fast, like the spinning ice skater pulling their arms.

The only thing I can think to suggest is - what if it was formed by material being deposited at its poles?

[willendure]

You can plug some numbers into this approximate model:

http://farside.ph.utexas.edu/teaching/3 ... de109.html

I think our intuition about this implying that the sun is not spinning is wrong. Its so heavy that it does not bulge very much.

[oz93666]

You can plug some numbers into this approximate model:

http://farside.ph.utexas.edu/teaching/3 ... de109.html

I think our intuition about this implying that the sun is not spinning is wrong. Its so heavy that it does not bulge very much.

I don't believe mass is a factor in mitigating this effect , the more mass the more centrifugal force , .. certainly the 'experts' who were working on this for decades were shocked , anyway from memory the gravity at the surface of the sun is only 12 times that of earth.

[oz93666]

This presumably means that the whole mass of the sun is not rotating , only the surface we see !

And that the sun has virtually no angular momentum , how is this possible in the current theory about the formation of the solar system ....

If the sun was formed from an equatorial disc of material, which was in any way rotating, then we would expect it to have significant angular momentum. We might also expect it to be rotating significantly fast,

Yes ...unbelievably fast , it's relatively slow rotation was a powerful indicator that the sun was binary, now it seems the sun doesn't even have that small angular momentum.

[willendure]

You can plug some numbers into this approximate model:

http://farside.ph.utexas.edu/teaching/3 ... de109.html

I think our intuition about this implying that the sun is not spinning is wrong. Its so heavy that it does not bulge very much.

I don't believe mass is a factor in mitigating this effect , the more mass the more centrifugal force , .. certainly the 'experts' who were working on this for decades were shocked , anyway from memory the gravity at the surface of the sun is only 12 times that of earth.

The ratio between the gravitational force and centrifugal force at the surface is the important factor. As the Sun is very heavy, gravity at its surface is pretty strong. The centrifugal force is relatively smaller, compared with say Earth or Saturn.

I don't think the 'experts' were shocked - we've suspected that the sun is very round for a long time. All that has happened recently is that we have confirmed it with accurate measurements.

[oz93666]

. As the Sun is very heavy......
I don't think the 'experts' were shocked - we've suspected that the sun is very round for a long time. All that has happened recently is that we have confirmed it with accurate measurements.

To be precise the sun is not heavy,floating in space it has no weight at all ( weight is the force experienced when a mass is under the influence of gravity) ....but it is very massive...

Quoting from the article ..... The results were a big surprise. "We were shocked," says Kuhn.

Kuhn suggests that turbulence under the surface is probably the cause. ....end quote


The calculations to find the expected bulge are very simple . The measured bulge cannot be explained easily, the interior cannot be rotating at the same speed as the surface.

[willendure]

The calculations to find the expected bulge are very simple . The measured bulge cannot be explained easily,

Plugging the numbers in the simplified model I posted yields 19km, the measured result is 10km. Its not a surprise, other than the astonishment of confirming such a strange seeming conclusion to actually be true.

[scowie]

I guess it's cos the sun is just much more rigid than earth and the other planets, i.e. it doesn't have an elastic lithosphere over it's solid core, or a liquid core for that matter. It is certainly not a ball of gas! See: http://www.thesurfaceofthesun.com

[oz93666]

The calculations to find the expected bulge are very simple . The measured bulge cannot be explained easily,

Plugging the numbers in the simplified model I posted yields 19km, the measured result is 10km. Its not a surprise, other than the astonishment of confirming such a strange seeming conclusion to actually be true.

Your right .... a search uncovers this from 'sciencemag'..."the sun's oblateness is about 25% smaller than previously estimated,"..... nothing to see here ....move along .... Another case of scientists sensationalizing their findings to get fame and fortune (more funding)...

Assuming the figures are accurate it can probably put down to the spin at the equator is not quite as fast , as pointed out on another forum.

[oz93666]

I guess it's cos the sun is just much more rigid than earth and the other planets, i.e. it doesn't have an elastic lithosphere over it's solid core, or a liquid core for that matter. It is certainly not a ball of gas! See: http://www.thesurfaceofthesun.com

That's a shocking link , scowie.... I quote from it ...." This visible neon plasma layer that we call the photosphere, and a thicker, more dense atmospheric layer composed of silicon plasma, entirely covers the actual rocky, calcium ferrite surface layer of the sun. The visible photosphere covers the actual surface of the sun, much as the earth's ocean" end quote

Neon plasma? calcium ferrite surface ? How can that be? Neon has a powerful red emition how come we don't see this , and spectrum indicating this and calcium ferrite? These dense elements, if present should fall to the center of a ball of hydrogen.

I have an open mind, and am still studying the link.

[oz93666]

I guess it's cos the sun is just much more rigid than earth and the other planets, i.e. it doesn't have an elastic lithosphere over it's solid core, or a liquid core for that matter. It is certainly not a ball of gas! See: http://www.thesurfaceofthesun.com

The evidence in your link is quite convincing ....Let me see if I've got this right , the sun is a shell of Iron , covered by the thin shells of differentiated elemental plasmas .... density of sun is 1.4 ....density of iron about 7, so the iron shell is about 20% of the volume ...a massive void inside ...of what ? how did this shell form?

Is there a thread on this forum covering the sun? (tried searching , with no luck)

[scowie]

I believe the sun to be a solid body, not a shell. I reckon the mainstream's mass and density figures are wrong, a result of their incorrect assumption that orbital mechanics is governed solely by the force of gravity (see my post here).

[CharlesChandler]

Plugging the numbers in the simplified model I posted yields 19km, the measured result is 10km.

I take this as evidence of a force other than gravity that is pulling inward. In my model, there are layers of opposite charges that are pulled together by the electric force (in addition to gravity). So this is an expectation in the "current-free double-layer" (CFDL) model.

[celeste]

I take this as evidence of a force other than gravity that is pulling inward.

Or a lack of other force, pulling the sun outwards at the equator. In Donald Scott's model, the sun is traveling along the center of a filament, where there are virtually no magnetic forces.