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Volunteers Use Annular Eclipse To Measure Sun More Accurately

Posted by timothy on from the maybe-it's-just-been-eating-differently dept.

Anonymous Squonk writes "The measurement of the sun currently in use was actually calculated over 120 years ago, and is off by hundreds of kilometers. Thousands of ordinary Japanese citizens worked together to improve this estimate. By measuring the borders of the 'ring of fire' effect of the recent eclipse, and using the known size and distance from the Earth of the sun, the radius of the Sun was measured as 696,010 kilometers, with a margin of error of only 20 kilometers."

52 of 75 comments (clear)

  1. Incidentally... by fuzzyfuzzyfungus · · Score: 4, Interesting

    I very strongly doubt that this is relevant on the scale of recorded human history and naked-eye observation; but doing all that mass-energy conversion and indiscriminate radiating must be slowly changing the sun's size, with some sort of balance between loss of mass and thermal expansion or contraction.

    I'm told that the 'expands and engulfs the inner planets' stage will be dramatic; but is the expectation before that event a very, very gradual shrinking or something more complex?

    1. Re:Incidentally... by Anonymous Coward · · Score: 2

      Well, I would assume a gradual expansion.

      Since the more reactions happen, the more mass it loses, thus the attraction on the nearby atoms/molecules lessen, thus allowing them to go a bit further away.

    2. Re:Incidentally... by SuricouRaven · · Score: 4, Interesting

      Don't forget the cycle too. Sunspots go up, sunspots go down.. that means a change in temperature, and as basically a ball of gas a change in temperature means a change in volume. I don't know how significent this pulsing effect would be, but if you can do measurements to 20km it might be measurable.

    3. Re:Incidentally... by Anonymous Coward · · Score: 5, Informative

      The Sun is growing right now and it is getting brighter by the day. This is not occurring at a rapid rate at the present time. It is due to the slow accumulation of helium in the core of the Sun. Helium doesn't undergo fusion at this time (not hot enough). The increase in helium would imply a decrease in the fusion rate, but due to maintaining a hydrostatic equilibrium, the temperature of the core increases and the fusion rate actually increases. This causes the radius to increase.

    4. Re:Incidentally... by Grayhand · · Score: 2

      Answer: Yes. The sun will continue to gradually shrink until it runs out of H to burn.

      Actually the opposite is true. Our sun is doomed to end up a red giant and eventually the Earth will be eaten by the sun. It's a middle aged star so there are billions of years to go.

    5. Re:Incidentally... by thoughtsatthemoment · · Score: 5, Informative

      To be more precise, the sun will become a red giant in about 5 billions, engulf the earth, and eventually fade as a white dwarf, whose volume is about the same as the earth.

    6. Re:Incidentally... by Hognoxious · · Score: 5, Funny

      You had me in a panic there - I thought you said millions.

      --
      Confucius say, "Find worm in apple - bad. Find half a worm - worse."
    7. Re:Incidentally... by Gaygirlie · · Score: 1

      Earth orbits the Sun .. pretty fast to cover 360 degrees in 365 days. Sun dies .. it loses mass (lots of it) because it burns it and radiates it away. Less mass means less gravity. Why doesn't anybody take into consideration the centripetal force acting on Earth (and everything else that orbits around the Sun)?

      My guess is that as the Sun's gravity weakens the Earth will be allowed to further away from the Sun.

      Earth's orbit will become more and more elliptical over time and will eventually either slingshot Earth out of the orbit and directly into the Sun.

      Earth however will be sort of slingshot eventually and it will either be catched by Jupiter (direct hit or very very very lucky but way too long shot catched in orbit as Jupiter's moon)

      I'm not a rocket-scientist or anything, but as far as I can see if Earth was getting slingshot out of orbit Jupiter would in no way have enough mass to catch it.

    8. Re:Incidentally... by CrimsonAvenger · · Score: 1

      Earth's orbit will become more and more elliptical over time and will eventually either slingshot Earth out of the orbit and directly into the Sun.

      Earth's orbit will increase in radius (without becoming more elliptical) as the Sun's mass decreases, and when the Sun goes red giant, the Earth will vaporize.

      Unless, of course, we move the Earth before then.

      I'm not a rocket-scientist or anything, but as far as I can see if Earth was getting slingshot out of orbit Jupiter would in no way have enough mass to catch it.

      I agree, you're not a rocket scientist.

      Yes, it might be possible for Jupiter to catch Earth. EXCEPT that Jupiter's orbit will also be changing as Earth's orbit changes, and there's no special reason to believe that the two will ever come close enough together to interact meaningfully.

      --

      "I do not agree with what you say, but I will defend to the death your right to say it"
    9. Re:Incidentally... by dwye · · Score: 2

      but doing all that mass-energy conversion and indiscriminate radiating must be slowly changing the sun's size

      This assumes that the Sun actually *has* a size, in a real, rather than purely mathematical sense. The outer layers of the Sun are a translucent vacuum. A harder vacuum than we were able to achieve for most of the 20th C, glowing like a neon light so that the visibility through those outer layers is about what the old London Pea Soup fogs were like. If we could view it in infrared, the Sun would have a larger "diameter" than this measurement, and of course smaller if measured from its ultraviolet image, or its X-ray image for that matter.

      They have managed to get the exact size of a balloon in the process of being blown up and released. Not its maximum size or its minimum, but merely that of one random moment in the cycle.

    10. Re:Incidentally... by progician · · Score: 1

      I never really considered this scenario, but there could be something in it. As a fixing note: the Sun is going to be a red giant first before it blows off the outer layers. The E=mc^2 means of course that only tiny fraction of the stars mass is transformed to energy due to the fusion. However, you have to still account for the mass that has been blown off by this energy. Most of this energy is turned to heat, light and radiation. While the heat/light accounts for no serious mass losses, I can easily imagine that the constant radiation over its roughly 10 billion year life time means quite a number of protons, electrons and neutrons leaving the Sun. Not to mention the coronal mass ejection where the solar wind is pushing out billions of tons of matter out of the Sun and hurtling toward the periphery of the Solar System. AFAIK, CME's can easily throw a magnitude of 10^12 kg of matter out. Over the period of 10 billion years, there are plenty of CME event. Just to stick to the wikipedia. An CME causing a loss in the average 1.6*10^12kg matter. The solar minimum rate of CME's is around once in 5 days, to the solar maximum's 3 times a day. I go with an arbitrary in-between value: 1 a day because it's easy to use :). (I don't have the time to go through the numerical integral of the solar cycles over its lifetime :)). 1 CME/day means around 3.65*10^12 eruptions over ten billion years, but let's go from our point of time (5.5 billion years remaining until the sun runs out of hydrogen): ~2.01*10^12 eruptions. This means in mass: 2*10^12 * 1.6*10^12 kg matter over the remaining days of the sun, 3.2*10^24kg. The Sun's mass is: 1.9891×10^30 kg So even if I calculate the overall mass loss of CME's, the sun would only lose: 1 / 621593.75 of her mass. To be honest, when I started to look up the facts and calculate, I thought I ended up with a new Nobel prize, but it seems nothing significantly will change in the orbit of Earth. Throw the eggs!

    11. Re:Incidentally... by K.+S.+Kyosuke · · Score: 1

      Earth's orbit will become more and more elliptical over time and will eventually either slingshot Earth out of the orbit and directly into the Sun.

      You can't slingshot unless you have three bodies. Sun, Earth...and what is the third one, larger than Earth, that Earth regularly approaches?

      --
      Ezekiel 23:20
    12. Re:Incidentally... by tqk · · Score: 1

      You can't slingshot unless you have three bodies.

      Pardon? How about we think of it as Earth falling into the Sun's gravity well far enough to be accelerated but not far enough to be captured. What happens next? I'd guess Earth gets flung off into the Oort cloud. That sounds like a two body slingshot effect to me.

      --
      "Tongue tied and twisted, just an Earth bound misfit ..." -- Pink Floyd.
    13. Re:Incidentally... by K.+S.+Kyosuke · · Score: 1

      You know what? Continue attending your high school and return back to me after you will have studied the law of conservation of energy. Look out especially for mechanical energy and its exchange between potential and kinetic form for a body on a free fall trajectory.

      --
      Ezekiel 23:20
    14. Re:Incidentally... by schroedingers_hat · · Score: 1

      Sunspots go up, sunspots go down..

      You can't explain that.

    15. Re:Incidentally... by schroedingers_hat · · Score: 2

      UUID goes up, intelligence goes down.
      You can't explain that.

    16. Re:Incidentally... by davester666 · · Score: 1

      Obviously the sun is getting hotter. Haven't you heard of global warming? If we don't do something soon, we'll get completely enveloped by the sun.

      --
      Sleep your way to a whiter smile...date a dentist!
  2. Manned Mission Needed by Scarletdown · · Score: 5, Funny

    I think to get the most accurate measurement, we need to send a manned mission to the sun and do it the old fashioned way, with a tape measure.

    Of course, to keep from burning up, they will have to go at night.

    --
    This space unintentionally left blank.
    1. Re:Manned Mission Needed by Black+Parrot · · Score: 3, Funny

      Or during an eclipse.

      --
      Sheesh, evil *and* a jerk. -- Jade
    2. Re:Manned Mission Needed by Grayhand · · Score: 4, Funny

      I think to get the most accurate measurement, we need to send a manned mission to the sun and do it the old fashioned way, with a tape measure.

      Of course, to keep from burning up, they will have to go at night.

      A waste of time and money. The eclipse proved that the sun is only slightly larger than the moon. Now you just have to use a tape measure to get an accurate size for the moon. Too bad the astronauts didn't think to take one.

    3. Re:Manned Mission Needed by Scarletdown · · Score: 1

      If doing it during an eclipse, it may be worthwhile to measure the sun's corona. Even better though would be to measure its Alaskan Amber.

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      This space unintentionally left blank.
    4. Re:Manned Mission Needed by qu33ksilver · · Score: 4, Funny

      Or during Winter.. You know this was a yahoo question. http://answers.yahoo.com/question/index?qid=20120430182228AAIk7uw

    5. Re:Manned Mission Needed by knarf · · Score: 1

      The eclipse proved that the sun is only slightly larger than the moon. Now you just have to use a tape measure to get an accurate size for the moon. Too bad the astronauts didn't think to take one.

      Who needs astronauts and tape measures when you have Three Wolf Moon? That moon don't look no bigger than a wolfs head, and wolfs we have a'plenty 'round here. Just grab one of 'm, measure its head and viola (sic).

      --
      --frank[at]unternet.org
    6. Re:Manned Mission Needed by __aaltlg1547 · · Score: 4, Funny

      Everybody knows a Corona is 12 ounces.

    7. Re:Manned Mission Needed by Scarletdown · · Score: 1

      Or during Winter.. You know this was a yahoo question. http://answers.yahoo.com/question/index?qid=20120430182228AAIk7uw

      Well, mine was inspired by a quip in an old indy comic back in the late 80s or early 90s called Space Ark. The bit there was:

      "How can we get close enough to the sun without burning up?"

      "Simple. We go at night."

      As for the Yahoo Answers post, I found it hilarious... hilarious that so many people actually thought the OP was being serious instead of seeing it for the silliness that it is.

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      This space unintentionally left blank.
    8. Re:Manned Mission Needed by Scarletdown · · Score: 1

      Just grab one of 'm, measure its head and viola (sic).

      Just don't forget that afterward, there is always room for cello.

      --
      This space unintentionally left blank.
    9. Re:Manned Mission Needed by wavedeform · · Score: 1

      I'm more interested in its exact Trumer Pils, myself.

  3. Re:Wouldn't it be great... by Nkwe · · Score: 1

    Sorry about the extra "the". It is late.

  4. Sorry, can't resist. by jtownatpunk.net · · Score: 3, Funny

    That's a relatively open weave and I can still see your... annular area.

  5. Re:Wouldn't it be great... by Black+Parrot · · Score: 4, Funny

    Wouldn't it be great if people learned foreign languages ? If people would allow foreigners to puplish in their on language ?...
    Yeah too much to ask, I guess.

    IMO everyone should be allowed to puplish in the language of their choice, so long as they do it in the privacy of their own home.

    --
    Sheesh, evil *and* a jerk. -- Jade
  6. Currently in use by zmooc · · Score: 3, Funny

    Good to see they focused their research on the sun that's currently in use and not on one of those old disposed ones!

    --
    0x or or snor perron?!
  7. Just jump through the Flaming Hoop of Death.... by rts008 · · Score: 1

    Your method suggests that extreme accuracy is required.

    You don't want to be off-center, otherwise you might singe your tail feathers.....;-)

    --
    Down With Slashdot BETA!!! I've been around the corner and seen the oliphant; you can only abuse me from your perspecti
  8. Wasn't this already known? by Anonymous Coward · · Score: 3, Informative

    NASA seemed to know it's 696,000km long before this experiment.

    1. Re:Wasn't this already known? by IWannaBeAnAC · · Score: 1

      Indeed. And the value elsewhere http://solarsystem.nasa.gov/planets/profile.cfm?Object=Sun&Display=Facts&System=Metric of 6.9551 x 10^5 km implies also an error of the order of 10km. But it differs by 500km (or 50 standard deviations)! This is an incredibly large difference between the measurements, given the error bars. Perhaps they are measuring different things, the radius at the equator won't be the same as the radius at the poles.

  9. I missed it by The+Evil+Atheist · · Score: 4, Funny

    Oh well, look on the bright side...

    --
    Those who do not learn from commit history are doomed to regress it.
  10. Re:Wouldn't it be great... by Baron+Eekman · · Score: 3, Informative

    English language version:
    http://ajw.asahi.com/article/behind_news/social_affairs/AJ201205250024

  11. Oh my god by Anonymous Coward · · Score: 5, Funny

    The measurement of the sun currently in use was actually calculated over 120 years ago, and is off by hundreds of kilometers.

    By the best available measurements the sun has shrunk by hundreds of kilometers in a space of 120 years... and in that time is when we've started using solar power. We should stop now while there's still some Sun left.

    1. Re:Oh my god by The+Evil+Atheist · · Score: 1

      We should stop now while there's still some Sun left.

      Too late. The remainder of Sun is too busy suing Google...

      --
      Those who do not learn from commit history are doomed to regress it.
  12. Define 'Sun' by EasyTarget · · Score: 3, Interesting

    Seriously; it has a atmosphere thousands of miles thick, with a fuzzy, boiling edge..

    The margin of error on this is ludicrous.

    Plus.. of course, it is continually boiling itself off onto space, so even if you could define a 'hard edge' to it, your measurements would become worthless in, say, a few million years ;-)

    --
    "Oops, I always forget the purpose of competition is to divide people into winners and losers." - Hobbes
    1. Re:Define 'Sun' by mister_playboy · · Score: 3, Informative

      Not to mention that it's probably not a perfect sphere, so a single radius doesn't capture its size.

      Wikipedia sayth:

      It is a near-perfect sphere, with an oblateness estimated at about 9 millionths, which means that its polar diameter differs from its equatorial diameter by only 10 km. As the Sun consists of a plasma and is not solid, it rotates faster at its equator than at its poles. This behavior is known as differential rotation, and is caused by convection in the Sun and the movement of mass, due to steep temperature gradients from the core outwards. This mass carries a portion of the Sun’s counter-clockwise angular momentum, as viewed from the ecliptic north pole, thus redistributing the angular velocity. The period of this actual rotation is approximately 25.6 days at the equator and 33.5 days at the poles. However, due to our constantly changing vantage point from the Earth as it orbits the Sun, the apparent rotation of the star at its equator is about 28 days. The centrifugal effect of this slow rotation is 18 million times weaker than the surface gravity at the Sun's equator. The tidal effect of the planets is even weaker, and does not significantly affect the shape of the Sun.

      So more round than you might think. :)

      --
      Do what thou wilt shall be the whole of the Law ::: Love is the law, love under will
    2. Re:Define 'Sun' by Hentes · · Score: 1

      This, it's a cloud of gas and defining its surface based on a given brightness (I guess, since this is an optical measurement) is pretty arbitrary.

  13. How accurate can it be ? by Alain+Williams · · Score: 4, Insightful

    Is this not somewhat akin to trying to measure the depth of a saucepan of boiling water ?

    1. Re:How accurate can it be ? by MalachiK · · Score: 2

      Yeah, but I'd guess it's pretty smooth when you consider the radius of the sun is of the order 10^9 m.

  14. In related news... by clickety6 · · Score: 1

    ... strange cases of sudden blindness have been sweeping across Japan, affecting thousands of citizens. Said one man, "I saw a blinding ring of light and then nothing! It was as though I had seen the nuclear breath of Gojira!"

    --
    ----------------------------------- My Other Sig Is Hilarious -----------------------------------
  15. Article unintelligible by __aaltlg1547 · · Score: 1

    Can we get it translated from the original Japanese to English by a person who speaks both languages fluently?

    1. Re:Article unintelligible by VortexCortex · · Score: 1

      Can we get it translated from the original Japanese to English by a person who speaks both languages fluently?

      Well, I don't have time to do the whole thing, but here's the gist: </moz-synch-lips> "Oh no Sun-Zilla!"

  16. Measured using known dimensions? by n7ytd · · Score: 2

    Japanese citizens worked together to improve this estimate. By measuring the borders of the 'ring of fire' effect of the recent eclipse, and using the known size and distance from the Earth of the sun, the radius of the Sun was measured as 696,010 kilometers, with a margin of error of only 20 kilometers."

    Wow! That's some breakthrough science!

  17. I'm still sore that it rained where I live by mark-t · · Score: 1

    I live in Western Canada, and we were supposed to get as much as 80% coverage of the sun at my location, near sunset. I even managed to secure some solar glasses especially for watching the event. It had been sunny for almost two whole weeks before the event, with barely a cloud in the sky. The eclipse happens and BAM... it's so freakin' overcast and rainy that you can't even tell which way the sun *IS*.

    Before sunset the next day, the clouds had cleared, and it's been sunny ever since.

    The universe hates me.

    --
    File under 'M' for 'Manic ranting'
  18. Correction Factors? by xfade551 · · Score: 1

    Since I can't read the full article (due to both registration and source language), can someone who does read Japanese, go through the article and check to see how through they were about correcting for atmospheric refraction, using proper ephemeris data for the base distance, etc? Somehow, I think SOHO, STEREO, and professional ground-based solar observatories have a better handle on this.

  19. Re:Wouldn't it be great... by mcgrew · · Score: 1

    So, how many languages do YOU speak?

    --
    Free Martian Whores!
  20. Re:Wouldn't it be great... by niado · · Score: 1

    whoosh..?

  21. Whole story is junk by Old+Wolf · · Score: 1

    Surely this is no news at all; the Sun has been measured as accurately as possible (given that it doesn't have a well-defined edge) by satellite telemetry long ago. This should perhaps be titled 'most accurate calculation by amateur Japanese without modern equipment' or something