The Sun's almost perfectly round shape baffles scientists

Aug 16, 2012
Image of the sun taken by the Solar Dynamics Observatory. Credit: NASA.

(Phys.org) -- The sun is nearly the roundest object ever measured. If scaled to the size of a beach ball, it would be so round that the difference between the widest and narrow diameters would be much less than the width of a human hair.

The sun rotates every 28 days, and because it doesn't have a , it should be slightly flattened. This tiny flattening has been studied with many instruments for almost 50 years to learn about the sun's rotation, especially the rotation below its surface, which we can't see directly.

Now Jeff Kuhn and Isabelle Scholl (Institute for Astronomy, University of Hawaii at Manoa), Rock Bush (Stanford University), and Marcelo Emilio (Universidade Estadual de Ponta Grossa, Brazil) have used the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory satellite to obtain what they believe is the definitive -- and baffling -- answer.

Because there is no atmosphere in space to distort the solar image, they were able to use HMI's exquisite image sensitivity to measure the solar shape with unprecedented accuracy. The results indicate that if the Sun were shrunk to a ball one meter in diameter, its equatorial diameter would be only 17 millionths of a meter larger than the diameter through its North-South pole, which is its .

They also found that the solar flattening is remarkably constant over time and too small to agree with that predicted from its surface rotation. This suggests that other subsurface forces, like or turbulence, may be a more powerful influence than expected.

Kuhn, the team leader and first author of an article published today in , said, "For years we've believed our fluctuating measurements were telling us that the sun varies, but these new results say something different. While just about everything else in the changes along with its 11-year , the shape doesn't."

This work was supported by NASA grants to Stanford University and the University of Hawaii.

Explore further: The source of the sky's X-ray glow

More information: "The Precise Solar Shape and Its Variability," by J.R. Kuhn et al., www.sciencemag.org/content/ear… 8/15/science.1223231

Related Stories

Sun's constant size surprises scientists

May 13, 2010

(PhysOrg.com) -- A group of astronomers led by the University of Hawaii's Dr. Jeff Kuhn has found that in recent times the sun's size has been remarkably constant. Its diameter has changed by less than one ...

Solar Dynamics Observatory goes for a spin

Apr 09, 2012

(Phys.org) -- On April 4, 2012, NASA's Solar Dynamics Observatory (SDO) did a 360. It rolled completely around its axis – something it does twice a year. In this movie, the dizzying view looks as if the ...

SDO helps measure magnetic fields on the sun's surface

Jan 20, 2012

(PhysOrg.com) -- Science nuggets are a collection of early science results, new research techniques, and instrument updates that further our attempt to understand the sun and the dynamic space weather system ...

Instrument to make detailed measurements of sun activity

Dec 05, 2007

For five years, Stanford research physicist Phil Scherrer and his team have raised a sophisticated space telescope with the attention a parent gives to a child, preparing it for the day when it flies away ...

Recommended for you

Titan offers clues to atmospheres of hazy planets

48 minutes ago

When hazy planets pass across the face of their star, a curious thing happens. Astronomers are not able to see any changes in the range of light coming from the star and planet system.

Having fun with the equation of time

58 minutes ago

If you're like us, you might've looked at a globe of the Earth in elementary school long before the days of Google Earth and wondered just what that strange looking figure eight thing on its side was.

The source of the sky's X-ray glow

20 hours ago

In findings that help astrophysicists understand our corner of the galaxy, an international research team has shown that the soft X-ray glow blanketing the sky comes from both inside and outside the solar system.

End dawns for Europe's space cargo delivery role

Jul 27, 2014

Europe will close an important chapter in its space flight history Tuesday, launching the fifth and final robot ship it had pledged for lifeline deliveries to the International Space Station.

User comments : 44

Adjust slider to filter visible comments by rank

Display comments: newest first

SatanLover
1.1 / 5 (55) Aug 16, 2012
"The sun rotates every 28 days, and because it doesn't have a solid surface, it should be slightly flattened. "

obviously you are full of dogma and not science.

"This work was supported by NASA grants "

Shame.
Glen_Lincoln
4.7 / 5 (32) Aug 16, 2012
The Earth is oblate because it rotates. Thats why rotating, systems flatten into a disc. That's not dogma, that's ordinary physics.
sstritt
3.5 / 5 (19) Aug 16, 2012
Perhaps the lack of an equatorial bulge is due to the balance between gravity and fusion pressure.
Deathclock
3.4 / 5 (16) Aug 16, 2012
It's because there is immense pressure, both outward and inward, and this pressure completely dominates any centrifugal force. I'm willing to bet it is ever so slightly elongated as expected, but the degree of this is tiny because the competing pressures of gravitational collapse and the explosive energy of the sun force it into a sphere so strongly that this dwarfs the centrifugal force.

FYI, I did not read the article... so this may be covered in the article

*edit* Dammit, beaten to it. I agree with sstritt
Caliban
2.7 / 5 (11) Aug 16, 2012
My bet is on internal turbulence/radiation pressure as the mechanism for redistributing force uniformly to offset rotational oblation.
Tangent2
3.5 / 5 (8) Aug 16, 2012

obviously you are full of dogma and not science.


Care to share your reasoning?
ValeriaT
3.4 / 5 (5) Aug 16, 2012
Perhaps the lack of an equatorial bulge is due to the balance between gravity and fusion pressure.
It may be so - the Sun exhibits gravitational brightening at poles, being slightly hotter there and the increased pressure of radiation counterfeits the gravity.
Kafpauzo
4.8 / 5 (18) Aug 16, 2012
"The sun rotates every 28 days, and because it doesn't have a solid surface, it should be slightly flattened. "

obviously you are full of dogma and not science.

"This work was supported by NASA grants "

Shame.

In this case the word "should" doesn't mean that there's something wrong with the sun. It means that our knowledge is faulty.

When the word "should" is used in this way, it means that the real sun is different from the theoretical sun that we get with the faulty calculations that we can currently make, based on our incomplete current knowledge. It means that the real sun is different from the way it would be if our knowledge were accurate.

So, it means that there's something wrong with our current knowledge.

When the word "should" is used in this way, it means that there's something we don't know, something we need to explore.

And they are doing just that. They are exploring this enigma, trying to find the missing knowledge.

That is the scientific approach.
SatanLover
1.2 / 5 (36) Aug 16, 2012
"The sun rotates every 28 days, and because it doesn't have a solid surface, it should be slightly flattened. "

obviously you are full of dogma and not science.

"This work was supported by NASA grants "

Shame.

In this case the word "should" doesn't mean that there's something wrong with the sun. It means that our knowledge is faulty.


ergo dogma, sigh 9 stupid people whom rated me :)

to explain further for whom do not understand .. (sigh you need more electrolytes!)

they are taught "it should be slightly flattened" yet the sun is not.

Why this dogma is not science? It is assumed the sun should be slightly flattened yet is not. Science is about observation not academic assumptions ergo dogma. Yes my friends there is dogma in science.
TheGhostofOtto1923
3.3 / 5 (47) Aug 16, 2012
Er perhaps this guy has the correct answer:

"IV. THE SUN IS A "CLOTHED NEUTRON STAR" formed by accreting iron-rich material on the pulsar (spinning neutron star) made at the supernova core"
http://www.omatum...igin.pdf

Whatever happened to him? Chain gang?

With kind regards...
Kafpauzo
4.8 / 5 (16) Aug 16, 2012
ergo dogma, sigh 9 stupid people whom rated me :)

_Not_ dogma. The reasoning is:

1. If we calculate, then our result is a more flattened sun.
2. But the real sun is not as flattened as our calculation says.
3. This means that our calculation is wrong.

they are taught "it should be slightly flattened" yet the sun is not.

No, they are _not_ taught that it should be slightly flattened. _Not_at_all!_

What happens is that they use mathematics. These mathematics give the correct result in almost all known cases.

But in the case of the sun, the math does not work right.

They are taught math that works right for almost all known cases. They are _also_ taught that their math is wrong in the case of the sun.

They know that it is wrong. They don't hide this. They don't deny it. They know it.

You need to learn English expressions better. You need to learn what the English word "should" means when it is used in this way. It means that they acknowledge that their math is wrong.
Infinion
3 / 5 (8) Aug 16, 2012
May 13, 2010
"Sun's constant size surprises scientists"

Mar 21, 2012
"Space observations of Mercury transits yield precise solar radius"

August 16, 2012
"The Sun's almost perfectly round shape baffles scientists"

glad we're making progress...
rwinners
1 / 5 (8) Aug 16, 2012
The earth, made up of much denser materials than the sun, is also quite flat. An orange skin has deeper/higher points relative to its diameter than the earth. Why should the sun, a ball of gas, be any rougher?
philw1776
3.8 / 5 (10) Aug 16, 2012
"Why should the sun, a ball of gas, be any rougher?"
Look at Jupiter, mostly a ball of H2. It's not round, quite oblate because of its rotation. The sun rotates far slower but doesn't show even the small oblate shape expected by pure Newtonian mechanics so scientists need to find what else is going on.
Torbjorn_Larsson_OM
5 / 5 (9) Aug 16, 2012
@ sstritt, Deathclock:

No, the so called hydrostatic balance, here between gravity and radiation pressure from photons released by fusion, is figured in. (Fusion products thermal pressure is secondary.)

Some rapidly rotating suns are the _least_ round coherent objects out there, since their gravity can keep them together despite immense rotation rates. Here is a series of flattened stars, with Archenar as the most flattened: http://www.davidd...lus.html

"And in 2003, astronomers discovered the equatorial diameter of the blue B3 main sequence star Achernar is 56% greater than its polar diameter, making it flattest star known."

That there are mechanisms that can actively balance out the deviation from a sphere that hydrostatic balance sets up in a spinning body is surprising but not impossible. Most likely thermal convection sets up the "turbulence" they suggest somehow acts as such a feedback.
Torbjorn_Larsson_OM
5 / 5 (6) Aug 16, 2012
The reason photon pressure is dominant to counteract gravity is interesting by the way. It is because stars are opaque and dense, so photons are trapped. It takes, IIRC, many 100 000s year for a photon to bounce its way up to the surface! (By a random walk in 3D.) Hence photon density in a star is immense, hence its pressure is dominated by photons.

When supernovas happens, things can change. In some supernovas it is believed it is pair production, mainly of electron-positron pairs IIRC, that sets up the explosion pressure.
Jitterbewegung
2.2 / 5 (12) Aug 16, 2012
How could the Sun have a neutron star inside it? Scientists can see through our transparent Sun so wouldn't they have noticed it?

http://science.na...27apr_1/
borc
4.6 / 5 (10) Aug 17, 2012
First of all I would like to open with a simple definition.
dog·ma/dôgm/Noun: A principle or set of principles laid down by an authority as incontrovertibly true
Now that we have established the meaning of the word at hand, let us reference the source: "Why this dogma is not science? It is assumed the sun should be slightly flattened yet is not."
Our friend here is suggesting that any established though regarding our natural world based on theory and mathematical equations that ends up being even slightly incorrect is by definition "dogma". Even when the same "people of authority" are actively taking part in studies to prove their "dogma" is NOT true. Dogma is supposed to be "incontrovertibly true". The very act of participating in this study eliminates any potential logical way of it being considering dogma. Please use the dictionary before posting, you make yourself look a fool. Maybe go drink some Gatorade, you need more electrolytes. It is, after all, what plants crave.
StarGazer2011
2.6 / 5 (8) Aug 17, 2012
Interesting results, esspessially in comparison with other stars which do flatten. I suppose the rotation is insufficient to overcome whatever forces tend to keep it spherical. I wonder for a given rotational period do larger or smaller stars flatten more?
DarkHorse66
4.6 / 5 (12) Aug 17, 2012
How could the Sun have a neutron star inside it? Scientists can see through our transparent Sun so wouldn't they have noticed it? /
@Jitter:"omatumr"(as referred to, in Otto's kindly provided link)or 'Oliver K Manuel' used to be the resident nutter who had all kinds of quack theories--including the delusion that our sun had a neutron core.He was still posting until somewhere during the latter half of last year.No one knows what has happened to him since he stopped.Maybe he has finally been sent to jail.(you can google him)So I'm not surprised that you might not be familiar with his (in)famous rants. I dare say that others will be happy to fill you in. Anyway, any time that you see someone referring to 'Oliver', 'neutron stars' etc, then it is tongue in cheek. Personally I am somewhat surprised to see this contribution by Otto taken seriously to the point of downrating by so many. I wonder how many others(who were exposed to Oliver)had same or similar thoughts;) Best Regards, DH66
dtyarbrough
1.7 / 5 (6) Aug 17, 2012
The magnetic field of the sun and thus the sun spots rotate in 28 days. Nobody really knows how fast the surface itself is actually moving.
Satene
1.4 / 5 (9) Aug 17, 2012
How could the Sun have a neutron star inside it?
The neutron star is exaggerated concept (the density of Solar core is about 150 times greater than that of water, whereas the density of neutron star is higher in many orders of magnitude), but the neutrino flux is concentrated into small central area of Sun, where the conditions aren't so different from the surface of neutron stars. What's interesting, this core rotates about three to five times faster than the rest of Sun. I presume, it exhibits directional flux of neutrinos/dark matter, because it affects the decay of radioactive elements with corresponding frequency. In this sense the core of Sun may behave like small neutrino pulsar.
Satene
1.7 / 5 (6) Aug 17, 2012
nobody really knows how fast the surface itself is actually moving.
Why the sunspots should rotate with different speed than the rest of surface? The sunspots are spatial vortices, which are embedded quite deeply into solar surface (they exhibit the Wilson effect) - so they should be dragged with it.
Satene
1.5 / 5 (8) Aug 17, 2012
Quite recently a new experimental evidence of the connection of radioactive decay to solar flares was given. It bring the questions for whole new physics. Not only we should explain, how the neutrinos can affect the speed of radioactive decay - they're too tiny and the flux of solar neutrinos is too sparse for it. But we should explain too, how the solar flares modulate the concentration of neutrinos. The flux of solar neutrinos is quite stable and it apparently doesn't contribute to this effect.
My explanation is, The escape velocity of neutrinos from Sun is just slightly higher, than the speed of neutrinos, which are in thermal equilibrium with CMBR fluctuations. The solar flares therefore interact with cold neutrinos cumulated around the Sun and they're displacing it. Note that Sun generates normal neutrinos, whereas the antineutrinos are dominant in primordial dark matter.
Satene
1.5 / 5 (8) Aug 17, 2012
The interaction of neutrinos with solar flares is most probably related to this study. The charged particles in solar plasma are moving with relativistic speed and such the may interact with neutrinos with elevated cross-section through gravitational waves. The similar effects were conjectured for interaction of gravitational waves with (fast moving electrons within) superconductors. In my opinion the neutrinos are solitons of gravitational waves in similar way, like photons are solitons of gravitational waves, so they should be affected with fast moving charged electrons and ions of solar plasma too. It may take another twenty years, before these effects will be considered and tested experimentally with caution.
TheGhostofOtto1923
3.1 / 5 (36) Aug 17, 2012
How could the Sun have a neutron star inside it? Scientists can see through our transparent Sun so wouldn't they have noticed it?

http://science.na...27apr_1/
Apparently Oliver claimswe can actually see the neutronium surface in pictures. Such is his deviation from the norm.
sstritt
1 / 5 (2) Aug 17, 2012
The reason photon pressure is dominant to counteract gravity is interesting by the way. It is because stars are opaque and dense, so photons are trapped. It takes, IIRC, many 100 000s year for a photon to bounce its way up to the surface! (By a random walk in 3D.) Hence photon density in a star is immense, hence its pressure is dominated by photons.

When supernovas happens, things can change. In some supernovas it is believed it is pair production, mainly of electron-positron pairs IIRC, that sets up the explosion pressure.

Thanks for the illumination!
dougie_fresh_007
2.5 / 5 (4) Aug 17, 2012
explosive energy of the sun force it into a sphere so strongly that this dwarfs the centrifugal force.


Centrifugal? no such force exists, although i agree that the apparent "smoothness" of the suns spherical shape is due to the balance of forces, i would also assume that the higher mass more spherical the shape becomes as the range where gravity becomes too weak to hold the "surface" of whatever we're discussing becomes smaller inversely proportional the mass ? perhaps ?
Kafpauzo
4.7 / 5 (6) Aug 17, 2012
Centrifugal? no such force exists,

That's a myth.

Depending on your frame of reference, you do experience it as a force, and calculate on it as such, and name it as such.

For example, in a spaceship that rotates to create a kind of artificial gravity, you experience a force that you can call gravitational or centrifugal or something else, depending on the viewpoint and frame of reference that you choose.

There's also a "Coriolis force" that "doesn't exist" unless you're in the frame of reference where it "does exist".

It's all a matter of frames of reference. You can't get physics right if you insist on only the "neutral" frame of reference, which is what you do if you insist on the myth.

http://en.wikiped...al_force
http://en.wikiped...is_force
dougie_fresh_007
5 / 5 (3) Aug 17, 2012

Depending on your frame of reference, you do experience it as a force, and calculate on it as such, and name it as such.

For example, in a spaceship that rotates to create a kind of artificial gravity, you experience a force that you can call gravitational or centrifugal or something else, depending on the viewpoint and frame of reference that you choose.



you mean to say "artificial gravity" is caused by the inward force the hull exerts on the persons feet, no outward force exists merely changing your path tangentially , it's obvious when you draw your force diagram
kevinrtrs
1.9 / 5 (17) Aug 18, 2012
Our sun is indeed a very, very special star. This is attested to by its extraordinary stability where flares that might be dangerous to us are a complete non-occurrence, compared to other stars of the same size and brightness where such flareups occur regularly within a hundred years. We've NEVER experienced anything like it. Special indeed.
So to find that it's almost completely circular/spherical should be no surprise; indeed one could almost certainly speculate that it's supreme stability is reflected in that perfect sphericity.
TheGhostofOtto1923
3 / 5 (34) Aug 18, 2012
Our sun is indeed a very, very special star. This is attested to by its extraordinary stability where flares that might be dangerous to us are a complete non-occurrence, compared to other stars of the same size and brightness where such flareups occur regularly within a hundred years. We've NEVER experienced anything like it. Special indeed.
-Not yet. That's what you meant to say right? Not in the last 6500 years anyway-

We haven't seen a major impact or a supervolcano but we know they can happen. Evidence tells us this.
Objectivist
4.2 / 5 (10) Aug 18, 2012
Except Oliver's answer to everything is neutron repulsion, and Kevin's answer to everything is God.
TheGhostofOtto1923
2.9 / 5 (30) Aug 18, 2012
So to find that it's almost completely circular/spherical should be no surprise; indeed one could almost certainly speculate that it's supreme stability is reflected in that perfect sphericity.
And why is that kev? Why would you conclude they are related when you have no idea what causes them? I suppose since your Jesus is a sun god that you might know something about it, but only in the same relative way as stability to roundness.

The sun is not perfect kev. It has SPOTS. it flares up from time to time and spits stuff out. Would god create something that's ALMOST perfect? Does he tolerate only a certain amount of imperfection? Was the sun in fact perfect before the Fall, and sin gave it blemishes?

I expect answers because I have follow-up questions.
dub1
1 / 5 (4) Aug 18, 2012
The facts seem to put a strain on extra-dimensional theories. All of them. A perfect 3-d structure. or 4-d if you choose to follow it through time. Reality is nice, beautiful even. Perfect circle string theorists?
rah
1.8 / 5 (5) Aug 19, 2012
I think that being a sphere also causes it to be round-ish.
Jaycubed
2.3 / 5 (3) Aug 19, 2012
I suspect that the reason for the extreme "roundness" of the Sun is due to the interaction of convection and gravity. The constant up & down movement of huge masses of material and the force of gravity are both perfectly symmetrical. The rotation of the Sun is probably too slow to have much of a bulging effect on the symmetry afforded by gravity & convection flows.
Jaycubed
2.3 / 5 (3) Aug 19, 2012
Add photon pressure as a third symmetrical component.
Mike_Massen
2 / 5 (4) Aug 19, 2012
Its all gas there is no surface its a probability distribution...

If there is a surface what is it - too hot for a liquid ?
vidyunmaya
1 / 5 (5) Aug 20, 2012
SuB: Perfect Sphere-COSMIC POT
Sun has to be a reflector to Cosmic Pot Sphere.
How is it Linked- http://www.scribd...rse-2003
Search Further-Space Cosmology Vedas Interlinks-http://vidyardhic...pot.com/
Raygunner
1 / 5 (3) Aug 20, 2012
The sun is alive, sunspots are pimples (better watch out when that zit pops!), and if it wants to be (almost) perfectly spherical it has every right to be. I'm going outside right now to beg forgiveness for - uh - something. So there you go.
TheGhostofOtto1923
2.7 / 5 (28) Aug 21, 2012
The sun is not perfect kev. It has SPOTS. it flares up from time to time and spits stuff out. Would god create something that's ALMOST perfect? Does he tolerate only a certain amount of imperfection? Was the sun in fact perfect before the Fall, and sin gave it blemishes?
I understand this is why the number 666 is such an abomination - it is made up of sixes which are ALMOST the perfect godly number 7. A perfect god would hate almost-perfect, wouldnt he kevin? Kevin?
Mike_Massen
1 / 5 (2) Aug 21, 2012
kevinrtrs proselytised again
Our sun is indeed a very, very special star.
Its pretty special at producing skin cancer for millenia before & after Moses & after Jesus, prob why they were black.
This is attested to by its extraordinary stability..
Yes, Sun is stable at producing cancers in many people for a long time..

Why didnt your god (at least) provide education ? Basic stuff!
We've NEVER experienced anything like it. Special indeed.
You mean you have ignored so much eg flares affecting satellites, power grids, people distracted by auroras in the north causing accidents !

kevinrtrs seems surprised by nature's optimum shape
So to find that it's almost completely circular/spherical should be no surprise..
'almost' kevinrtrs ! You saying your god is an anthropomorphic 'almost' deity ? Is that why it cant produce an indestructible bible to give to all 11 year old kids.

Ooops it cant stop kids dying young all over the world can it, pathetic impotent deity indeed !
Vendicar_Decarian
2 / 5 (4) Aug 22, 2012
Clearly this shape can only be explained if the Sun is actually a solid ball of non-rotating Iron.