Equation of centre

Japanese: 中心差 - ちゅうしんさ（英語表記）equation of centre

The difference between the true anomaly and the mean anomaly of a mass in Keplerian motion. The magnitude of the anomaly depends on the eccentricity of the ellipse, and is 0 when the motion is circular. The greater the eccentricity, the greater the anomaly. In other words, according to the law of areal velocity, a celestial body has a fast angular velocity at perigee and a slow angular velocity at apogee. If we consider a hypothetical celestial body that moves with a uniform angular velocity over time, the position of that celestial body in its orbit will differ from that of the true celestial body, and the greater the eccentricity, the greater this difference will be. In the case of the Sun, the amplitude of the leading term in the anomaly is 1.9 degrees, and it is one of the causes of the equation of time.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

ケプラー運動する質点の真近点離角と平均近点離角の差。中心差の大きさは，楕円の離心率に依存していて，円運動のとき0となり，離心率が大きいほど中心差は大きくなる。すなわち，天体は面積速度の法則に従って，近地点では速い角速度を持ち遠地点では遅い。いま時間とともに一様な角速度で進む仮想の天体を考えると，その天体は真の天体と軌道上の位置がそれ，離心率が大きいほど，この差は大きくなる。太陽の場合，中心差の主要項の振幅は1.9度であって，均時差の原因の一つである。

出典　株式会社平凡社世界大百科事典第２版について　情報

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