Yes, GALAXIES is a Scrabble word!

Letter values in Scrabble US: G 2, A 1, L 1, A 1, X 8, I 1, E 1, S 1.

Is it a valid word?

GALAXIES is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a splendid assemblage (especially of famous people)
tufted evergreen perennial herb having spikes of tiny white flowers and glossy green round to heart-shaped leaves that become coppery to maroon or purplish in fall
(astronomy) a collection of star systems; any of the billions of systems each having many stars and nebulae and dust

Also: galax urceolata, extragalactic nebula.

Not playable in Scrabble US: WANDFLOWER, BEETLEWEED.