close approach
Astronomical term for a celestial body passing very near another, especially a planet's close approach to Earth.
今夜、火星が地球に大接近する。
Tonight, Mars will make a close approach to Earth.
Compound of 大 (dai, 'big, great') + 接近 (sekkin, 'approach'). The exact historical derivation is uncertain, but the word is used in modern Japanese primarily as an astronomical term.