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Sun Is Roundest Natural Object Known

Posted August 20, 2012 11:07 AM

From National Geographic News:

The sun is the roundest natural object ever precisely measured, a discovery that may solve past climatic mysteries, new observations show.

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#1

Re: Sun Is Roundest Natural Object Known

08/20/2012 12:20 PM

How does one precisely measure an object that does not have discrete surface boundaries?

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#3
In reply to #1

Re: Sun Is Roundest Natural Object Known

08/20/2012 4:22 PM

AH, if you *had* to, how would you approach the problem? It's this sort of thing wot makes it fun, yes? :)

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#4
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Re: Sun Is Roundest Natural Object Known

08/20/2012 4:32 PM

I guess an extra long tailor's tape is out of the question?

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#5
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Re: Sun Is Roundest Natural Object Known

08/20/2012 5:28 PM

No, as long as I get the contract! :)

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#6
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Re: Sun Is Roundest Natural Object Known

08/20/2012 6:17 PM

Don't forget the sunblock!

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#7
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Re: Sun Is Roundest Natural Object Known

08/20/2012 6:22 PM

Do it at night. We've gotta cut costs! :)

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#8
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Re: Sun Is Roundest Natural Object Known

08/20/2012 8:05 PM

That is genius!

You wouldn't be captain of the B Ark by any chance?

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#16
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Re: Sun Is Roundest Natural Object Known

08/21/2012 6:54 PM

It was done photographically/photometrically, so I'd guess they scanned the images using an algorithm to detect a specific rise/fall in luminance. If the Sun is truly spherical it wouldn't matter what constant you used, the 50 percent point, the 5 percent point, the 1/e2 point, or whatever. You'd set your edge-detection algorithm to some number and find out that, no matter what number you chose, the diameter for that number was always the same, for any positional angle, at any point in the satellite's orbit around the sun.

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#17
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Re: Sun Is Roundest Natural Object Known

08/21/2012 7:28 PM

Bingo!

(AH, I'm still game for that contract lol)

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#19
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Re: Sun Is Roundest Natural Object Known

08/21/2012 8:02 PM

Well, I was gonna say do it a night, but you beat me to it.

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#20
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Re: Sun Is Roundest Natural Object Known

08/21/2012 10:00 PM

Ah, the race goeth to he/she/it wot hath connected to the fasteth CR4 server!

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#2

Re: Sun Is Roundest Natural Object Known

08/20/2012 1:12 PM

It would seem the Sun is in a gravitationally balanced orbit...

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#9

Re: Sun Is Roundest Natural Object Known

08/21/2012 12:40 AM

It ought to be slightly oblate from rotation--how much, though?

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#10
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Re: Sun Is Roundest Natural Object Known

08/21/2012 1:25 AM

About as much as Jupiter would be if it's 'day' were 28 Earth days long (rather than 10 hours), i.e., 'not too', but certainly more than it is. Some speculate that the Sun is so spherical because the convection currents within the Sun are much stronger than previously assumed. This seems to make sense, as these currents have no preferential direction with respect to the Sun's spin axis. Stronger currents would tend to swamp the effects of the Sun's spin on its shape, by pushing the 'surface' (chromosphere) outward and fairly uniformly overall. Were these currents to somehow stop, I'm sure the Sun would both be somewhat smaller and assume a more oblate shape consistent with its rotation, IMO. I would hazard a guess that the Sun's *density* cross-section *is* oblate, however. Again, IMO.

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#11
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Re: Sun Is Roundest Natural Object Known

08/21/2012 1:37 AM

That makes sense. I haven't done any calcs on it, or anything.

This resembles the situation of Kansas being flatter than a pancake (in scale, that is).

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#12

Re: Sun Is Roundest Natural Object Known

08/21/2012 6:41 AM

Hang on a minute

"If the sun were a meter-wide (3.3-foot-wide) beach ball, Kuhn said, the variation in the sun's shape from the highest to the lowest point would be about 17 microns-less than the width of a fine human hair, according to the SDO measurements."

This doesn't sound very impressive compared to.

"Were the electron scaled up to the size of the solar system, any deviation from its roundness would be smaller than the width of a human hair, the team said."

From a recent news article:-

http://www.guardian.co.uk/science/2011/may/25/electrons-round-cosmos

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#13
In reply to #12

Re: Sun Is Roundest Natural Object Known

08/21/2012 7:42 AM

Let's see that picture of the electron again.....cause I don't remember anything round....sounds like hooey to me...

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#14
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Re: Sun Is Roundest Natural Object Known

08/21/2012 2:26 PM

Round in the Classical sense. In the QM sense electrons have no size whatsoever.

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#15
In reply to #14

Re: Sun Is Roundest Natural Object Known

08/21/2012 2:45 PM

Yes, that kind of confounds me, too. Either they are a probability wave or they are a point charge of no dimension, yet in classic physics they can be determined to have a specific radius.

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#18
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Re: Sun Is Roundest Natural Object Known

08/21/2012 7:30 PM
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