Several parts combine into one character.

星 is a phono-semantic character: 日 (sun, a shining point) carries the meaning, 生 (to be born) lends the sound. It once had three shining points (晶) on top, later reduced to one — light risen in the night sky, a star. 生 lends the sound "xīng/seong."

Mandarin: xīng, 1st tone. 星星 (xīngxing, star), 明星 (míngxīng, a celebrity / star), 星期 (xīngqī, week / day of week — "star cycle"), 火星 (huǒxīng, Mars). Chinese counts the days of the week with 星 — 星期一 (Monday), 星期二 (Tuesday).

Japanese: on-readings セイ (sei) and ショウ (shō), kun ほし (hoshi). 星 (hoshi, star), 星座 (seiza, constellation), 衛星 (eisei, satellite), 明星 (myōjō, the morning/evening star — a ショウ reading), 流れ星 (nagareboshi, shooting star). In Japan ほし is also detective slang for a suspect or culprit.

Korean hanja-sound "seong": 星座 (seongjwa, constellation), 衛星 (wiseong, satellite), 流星 (yuseong, meteor), 北極星 (bukgeukseong, the North Star).

Memory aid: a sun-like light being born (生) — a small sun born into the night sky, a star.