noun
plane of the ecliptic
Astronomical term referring to the flat plane in which Earth orbits the Sun.
惑星の軌道は黄道面に近い。
The orbits of the planets are close to the plane of the ecliptic.
黄道 is the ecliptic itself (the Sun's apparent path), while 黄道面 is the plane containing that path.
Compound of 黄道 (ecliptic) and 面 (plane, surface). The term is a direct translation of the English 'plane of the ecliptic'.