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How Big is the Sun, Really?
Sky and Telescope ^ | 3/21/2012 | Kelly Beatty

Posted on 03/23/2012 1:29:41 AM PDT by U-238

With all the attention that astronomers have lavished on old Sol over the centuries, you'd think that by now they'd know its diameter to, oh, 10 or 12 significant digits.

During the past 40 years, astronomers have attempted to measure the Sun's sizedozens of times using various methods. The dashed line corresponds to a radius of 696,000 km, the value most often used.

While the Sun's girth has indeed been measured dozens of times over the past 40 years, the results haven't converged on a single value and scatter by as much as ± 0.1%. One big reason is that, though some measurement techniques are extremely precise, their accuracy suffers because of the turbulence induced by Earth's atmosphere. Most often astronomers use a compromise value of 865,000 miles (1,392,000 km).

So Marcelo Emilio (State university of Ponta Grossa, Brazil) has teamed with observers at the University of Hawaii and Stanford to approach this measurement with, literally, space-age techniques. They used images taken by the Michelson Doppler Imager (MDI) aboard NASA’s Solar and Heliospheric Observatory (SOHO), homing in on transits of the planet Mercury across the solar disk in 2003 and 2006.

This makes perfect sense. The spacecraft sits at the L1 Lagrange point, a million miles from Earth, and Mercury has nothing but the barest wisps of atmosphere — a made-to-order combination for crisp images.

(Excerpt) Read more at skyandtelescope.com ...


TOPICS: Science
KEYWORDS: astronomers; astronomy; astrophysics; catastrophism; science; soho; sol; solarsystem

1 posted on 03/23/2012 1:29:43 AM PDT by U-238
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To: SunkenCiv; KevinDavis

Ping


2 posted on 03/23/2012 1:31:30 AM PDT by U-238
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To: U-238
because of the turbulence induced by Earth's atmosphere...

Earth's atmosphere? What can cause that? Must be Earth's Anthropomorphic Turbulence... or EAT! Only one way to deal with that... might take many Trillion$, but we gotta do it. Do we have consensus yet?

3 posted on 03/23/2012 1:41:35 AM PDT by C210N (Mitt "Severe Etch-a-Sketch" Romney is the front-runner? Seriously??)
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To: U-238
"How Big is the Sun, Really?"

That's an easy one:

It's about the size of a grapefruit...

4 posted on 03/23/2012 1:50:09 AM PDT by Mad Dawgg (If you're going to deny my 1st Amendment rights then I must proceed to the 2nd one...)
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To: Mad Dawgg

I like it..


5 posted on 03/23/2012 1:55:06 AM PDT by pieceofthepuzzle
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To: Mad Dawgg

That kinda reminds me of my last prostate exam.


6 posted on 03/23/2012 2:08:52 AM PDT by fieldmarshaldj
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To: U-238

Even though the sun is so far away, it manages to have a major effect on our lives here at Earth. Within the next hour, it is going to appear once again on the eastern horizon here in New England - at least I hope it does, otherwise we are in for one hell of a dark, cold day here.


7 posted on 03/23/2012 2:25:20 AM PDT by SamAdams76 (I am 52 days away from outliving Phil Hartman)
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To: U-238
It is obvious to anyone who has seen a total solar eclipse (I did back in 1969) that the moon and sun are the same size. Which proves that because of our planet's greater mass, both bodies instead orbit the earth and all this nonsense since Copernicus has been a Leftist conspiracy designed to empower the Liberal Democrats in the government's regulation of gravity—and the enforcement arm will be called Earth Panels.

Vote Republican in November and you can kiss the ground goodbye.

8 posted on 03/23/2012 3:08:17 AM PDT by Happy Rain ("Rick Santorum--Public Enemy #1 of Leftists, RINOs and the GOP Establishmnet.")
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To: U-238

The sun is a big ball of hot gas - it does not have a sharply defined circumference and hence no precise diameter.


9 posted on 03/23/2012 3:15:40 AM PDT by Moltke (Always retaliate first.)
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To: U-238

I’ve always wanted to know just how big the sun is. Within 0.1%.


10 posted on 03/23/2012 3:53:56 AM PDT by count-your-change (You don't have to be brilliant, not being stupid is enough.)
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To: count-your-change
Science starts at 1%.

That's why there is no Climate Science - those claiming to be "Climate Scientists" can't even predict the sign much less the magnitude.

11 posted on 03/23/2012 4:27:41 AM PDT by Paladin2
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To: Paladin2

I’m going to go out on a limb here and suggest a ball of hydrogen plasma 850,000 miles in diameter with a fusion reaction core converting tons of matter per second just might be larger factor in global warming than my SUV.


12 posted on 03/23/2012 4:38:53 AM PDT by 6SJ7 (Meh.)
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To: 6SJ7
Nah, it's your CO2.
13 posted on 03/23/2012 4:49:45 AM PDT by Paladin2
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To: U-238

I tried to measure it a couple of times, but my tape measure kept melting.


14 posted on 03/23/2012 6:10:10 AM PDT by smokingfrog ( sleep with one eye open (<o> ---)
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To: smokingfrog

You should have measured it from the dark side.


15 posted on 03/23/2012 6:13:07 AM PDT by Larry Lucido (My doctor told me to curtail my Walpoling activities.)
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To: U-238

What are they measuring it for, a tuxedo? Just leave a few extra inches in the waist and it’ll be fine.


16 posted on 03/23/2012 6:15:01 AM PDT by Larry Lucido (My doctor told me to curtail my Walpoling activities.)
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To: Happy Rain
It is obvious to anyone who has seen a total solar eclipse (I did back in 1969) that the moon and sun are the same size.

I don't believe there was a total solar eclipse during 1969. Where did you see this? There was an annular eclipse in 1969, but seeing that would have led you to conclude that the sun is bigger than the moon!

(I've been in the path of totality twice, but the only total eclipse I actually saw was on March 7, 1970, on Nantucket Island.)

ML/NJ

17 posted on 03/23/2012 6:42:37 AM PDT by ml/nj
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To: ml/nj

“the only total eclipse I actually saw was on March 7, 1970, on Nantucket Island”

Did you fly your Lear Jet up there? Geez you’re vain.. You probably think this post is about you.


18 posted on 03/23/2012 7:46:38 AM PDT by PilotDave (No, really, you just can't make this stuff up!!!)
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To: PilotDave

LOL!


19 posted on 03/23/2012 7:49:48 AM PDT by Hegewisch Dupa
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To: U-238

They seem to be assuming that it has a constant diameter. Isn’t it possible that the sun’s diameter changes from time to time? As a great big ball of burning gas and plasma it might swell up and contract back again, if only a little, every now and then.

And why exactly do we need to know this with such precision? Are we buying it a new pair of pants?


20 posted on 03/23/2012 8:03:46 AM PDT by Ramius (Personally, I give us one chance in three. More tea anyone?)
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To: PilotDave
Did you fly your Lear Jet up there? Geez you’re vain. You probably think this post is about you.

Nope. Didn't have my ticket yet then. (And I never was PIC of anything with more than one propeller.)

Carly Simon was singing about the Nova Scotia eclipse which occurred on July 10, 1972, BEFORE Saratoga opened on July 31 of that year. SHE's so STUPID.

For those who don't know the song's lyrics are in part:

Well I hear you went up to Saratoga and your horse naturally won
Then you flew your lear jet up to Nova Scotia
To see the total eclipse of the sun
ML/NJ
21 posted on 03/23/2012 8:38:18 AM PDT by ml/nj
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To: All

Hey, check out that Sun up there. That sucker’s huge.

Tiny E.


22 posted on 03/23/2012 8:42:44 AM PDT by WillVoteForFood
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To: Happy Rain
It was still true in 1999 (I was lucky enough to see the total eclipse that year which was visible in parts of Europe--lucky because the clouds broke just in time to watch the total phase). I think there is a line in Samuel Taylor Coleridge's "Rime of the Ancient Mariner" about the sun appearing no bigger than the moon.

The next total eclipse visible in the US will be on August 21, 2017...the first in the 48 states since 1979.

23 posted on 03/23/2012 8:56:25 AM PDT by Verginius Rufus
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To: PilotDave

thank you Carly.


24 posted on 03/23/2012 11:27:24 AM PDT by brivette
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To: Ramius
They seem to be assuming that it has a constant diameter. Isn’t it possible that the sun’s diameter changes from time to time?


The Sun expands and contracts because it made from gas. Gravity pulls the sun together and the heat and light of the fusion process expands it. So there is a balance between the forces and has a steady radius. Why scientists want to know?Maybe they want to know how far along the Main Sequence the Sun in evolving. See Hydrostatic equilibrium
25 posted on 03/23/2012 6:01:13 PM PDT by U-238
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To: U-238; 75thOVI; agrace; aimhigh; Alice in Wonderland; AndrewC; aragorn; aristotleman; ...

Thanks U-238.

Also, if memory serves, the Sun's cornea ('surface') pulses on some interval, I think it's about 45 minutes, so the diameter varies between two values.


Thanks .




26 posted on 03/23/2012 6:50:54 PM PDT by SunkenCiv (I come to bury Caesar, not to praise him)
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To: ml/nj

There was a total solar eclipse visible to parts of the South Eastern United States in 1969—to the best of my knowledge—maybe it was 1970 or 1968—but I remember my motther—irrationally protective—fussed at me because I watched it without vision filters after it went total—it was so weird cuz the night creatures started singing and the day creatures went silent and the corolla was awesome—a cosmic ring of flashing electric emanations that unlike lightning were straight and variable in length—to me on the ground it was like a horizon to horizon dark glass soup bowl was put down on my back yard.


27 posted on 03/24/2012 8:29:11 AM PDT by Happy Rain ("Rick Santorum--Public Enemy #1 of Leftists, RINOs and the GOP Establishmnet.")
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To: Happy Rain
There was a total solar eclipse visible to parts of the South Eastern United States in 1969—to the best of my knowledge—maybe it was 1970 or 1968—but I remember my motther—irrationally protective—fussed at me because I watched it without vision filters after it went total

I think the eclipse you are referring to was the same one as the one I saw on Nantucket on March 7, 1970. Here's a map of the path it took:

There are always a lot of warnings before an eclipse about the danger of looking directly at the sun during the eclipse. This is because almost everyone will be looking at a partial eclipse. Even those in the path of totality usually get about an hour before and after totality of waxing and waning partial eclipse. During the short period of totality though (and not a second before or a second after) looking directly at the sun is no more dangerous than looking at the full moon. I actually looked directly at the eclipse through an unfiltered telescope for about 30 seconds. Seeing the red-orange solar prominences was quite spectacular. Something like this:
This isn't my picture, and my recollection is that I saw more orange than appears in this picture.

ML/NJ

28 posted on 03/25/2012 8:27:51 AM PDT by ml/nj
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To: ml/nj
That must have been it—I was living in Goose Creek, SC at the time—which is about halfway between Charleston and Summerville- almost smack dab on the redline.

One of those very intense moments of my youth—I was awestruck.

29 posted on 03/25/2012 8:50:18 AM PDT by Happy Rain ("Choose between Rick or Mitt or you have already chosen Mitt.")
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