star, spot, dot, mark
星 centers on a small bright point in the sky or on a surface: a star, a spot, a dot, or a mark. The meanings share the idea of a distinct, often luminous, point.
星 combines 日 (sun) and 生 (life/birth), originally representing the idea of stars as 'living' or 'bright' celestial bodies. The modern form preserves this semantic combination.
The sun 日 above new life 生: imagine stars as suns being born in the night sky, each a bright spot or dot.
For セイ, picture a star saying its own name: 'Say, I'm a star!' — 'Say' cues セイ, and the star speaks its bright identity.
star (usu. excluding the Sun); planet (usu. excluding Earth); heavenly body
planet
(natural) satellite; moon
Mars (planet)
constellation
starry sky
comet
Jupiter (planet)
asteroid
dazzling victory
Venus (planet)
Saturn (planet)
shooting star; falling star; meteor
star
morning star; Venus
white circle; white star
Stars and Stripes (US flag)
nova
black spot; black dot; bull's-eye
Mercury (planet)
(mark indicating) a win
Uranus (planet)
Neptune (planet)
giant star