世界最高精度で太陽の大きさを測定（Measure the magnitude of the sun in the world's highest accuracy）

今回の金環日食では、日本の天文学者らで組織する観測チームが世界最高の精度で太陽の大きさの測定に挑む。
　太陽の大きさは、国際天 文学連合（ＩＡＵ）で１８９１年に半径６９万６千キロとされたが、観測機器の精度限界から数百キロの誤差がある。そこで２００７年に打ち上げた月周回衛星 「かぐや」の観測データと金環日食を利用して、１ケタ高い精度で大きさを決定しようという試みだ。
金環日食の終了時は月面にそびえる山が太陽の縁を隠し、光のリングが途切れる。この瞬間の時刻をＧＰＳ（衛星利用測位システム）時計や撮影記録などにより、千分の１秒以下まで精密に計測する。
　ＩＡＵの太陽半径を基に予測した終了時刻と、実測した時刻の差から半径を計算。終了時刻が予測より早ければ、半径はＩＡＵの数値より小さく、遅ければ大きくなる。
　算出に必要な月面の山の高さは、かぐやの観測データから１０メートルの精度で把握できている。月面の１０メートルが隠す太陽表面の大きさは約４キロで、地球や月の位置に関する誤差などを加味しても、全体の測定誤差は数十キロに抑えられる見込みだ。
　観測は関東地方から九州地方にかけての１８地点で予定。発起人の一人である大西・長野工業高等専門学校教授（天文学）は「観測点が増えれば測定精度も上がる。秋までに最初の報告をしたい。当日はぜひ晴れてほしい」と意気込む。金環日食が日本の広範囲で観測できる恩恵で太陽の大きさが正確に測定できるんでしょうね。当日は本当に晴れて欲しいですね。


In this annular eclipse, a team of astronomers from the observation organized by Japan's challenge to measure the size of the sun in the world's best precision.

The size of the sun, have been one thousand and 690,006 km in radius in 1891 (IAU) International Astronomical Union, there is an error of several hundred kilometers from the limits of accuracy of observation equipment. I tried using the annular solar eclipse observation data and satellite was launched in 2007 lunar orbiter "Kaguya" there, which attempts to determine the size of a digit is a high degree of accuracy.

At the end of the annular solar eclipse is to hide the edge of the sun towering mountains on the moon, ring of light is interrupted. By shooting, such as watches and records (global positioning system), to measure precisely to less than a thousandth of a second GPS time of this moment.

End time and calculate the radius based on the predicted solar radius of the IAU, from the difference between the measured time. Than expected as early as the end time, the radius is smaller than the number of IAU, the greater the slower.

The height of the mountain on the lunar surface is required to calculate, that can grasp with an accuracy of 10 meters from the observation data and furniture. Hide the size of the solar surface is 10 meters of the lunar surface is about 4 km, and also taking into account the error on the position of the earth and the moon, the overall measurement error is expected to be reduced to several tens of kilometers.

At the point of observation is scheduled from 18 of the Kyushu region during the Kanto region. Be enthusiastic about (astronomy), "I want to the first report by autumn. Also increases measurement accuracy The more observation points. Want a sunny day means" with Professor Naganokogyokotosenmongakko-Onishi, who is one of the founders. I will not be able to accurately measure the size of the sun in the annular solar eclipse can be observed benefit in a wide range of Japan. I hope the day is really sunny.