noun
exomoon; extrasolar moon
A moon orbiting a planet outside our solar system. Rare technical term in astronomy.
太陽系外衛星の存在は、まだ直接確認されていない。
The existence of exomoons has not yet been directly confirmed.
Refers to an extrasolar planet (exoplanet), while 太陽系外衛星 refers specifically to a moon orbiting such a planet.
Compound of 太陽系外 (extrasolar) and 衛星 (satellite/moon). A modern scientific term.