noun
direct motion; prograde motion
Astronomical term for the apparent eastward motion of a celestial body relative to the fixed stars, opposite of retrograde motion (逆行運動).
See also: 逆行運動
The direct motion of a planet appears to move eastward as seen from Earth.
順行運動と逆行運動は、天文学の基本的な概念だ。
Direct motion and retrograde motion are fundamental concepts in astronomy.