大行星 (dàxíngxīng): major planet

大行星 distinguishes the eight 'real' planets from 小行星 (xiǎoxíngxīng — 'asteroid', literally 'small planet') and 矮行星 (ǎixíngxīng — 'dwarf planet'). Older Chinese texts say 九大行星 (jiǔ dàxíngxīng) reflecting the pre-2006 nine-planet count that included Pluto.

memory

Read it as 大-行星 (dà-xíngxīng), 'big planet'. Note 行 here is xíng, not háng — 行星 literally 'travelling star', a calque of the Greek 'planētēs' (wanderer).