If three celestial bodies in any solar system are lined up, you could say they’re aligned in syzygy. Often this applies to the sun, the moon, and the earth, but any planets can be in syzygy.
To pronounce syzygy, accent the first syllable: “SIZ-eh-gee.” The most common occurrence of syzygy is when the sun, the moon, and the earth are lined up, which happens during the time of a new moon or a full moon. Syzygy can sometimes cause eclipses, and it also affects the tide. If you live in a different solar system, you can still use the word — it can apply to heavenly bodies anywhere that line up straight.